Operational Status and Power Upgrade Prospects of the

arXiv:1411.5540v1 [physics.acc-ph] 20 Nov 2014
Operational Status and Power Upgrade Prospects of the
Neutrino Experimental Facility at J-PARC
Taku Ishida for the T2K Beam Group
J-PARC Center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan
E-mail: taku.ishida@kek.jp
(Received Nov. 4, 2014)
In order to explore CP asymmetry in the lepton sector, a power upgrade to the neutrino experimental
facility at J-PARC is a key requirement for both the Tokai to Kamioka (T2K) long-baseline neutrino oscillation experiment and a future project with Hyper-Kamiokande. Based on five years of
operational experience, the facility has achieved stable operation with 230 kW beam power without
significant problems on the beam-line apparatus. After successful maintenance works in 2013−2014
to replace all electromagnetic horns and a production target, the facility is now ready to accomodate a 750-kW-rated beam. Also, the possibility of achieving a few to multi-MW beam operation is
discussed in detail.
KEYWORDS: neutrino oscillation, neutrino super-beam, T2K, Hyper-Kamiokande, CP violation
1. Neutrino Experimental Facility at J-PARC
The neutrino experimental facility at J-PARC was built to produce the world’s highest intensity
neutrino beam and to facilitate leading research into neutrino physics. Its beam power is rated at 750
kW. In 2013, the facility was operated at 230 kW, which led to the first-ever definitive observation
of electron neutrino appearance by Tokai-to-Kamioka (T2K) [1], a long-baseline neutrino oscillation
experiment between J-PARC and Super-Kamiokande (Super-K). The observation illustrates that conventional super-beam experiments really come closer to seeing CP violation: T2K has the opportunity
to establish 3 σ evidence of CP violation by accumulating full statistics of data [2]. Furthermore, a
future project, the long-baseline neutrino oscillation experiment from J-PARC to Hyper-Kamiokande
(Hyper-K, whose planned fiducial volume is ∼25 times larger than that of Super-K), will allow 5 σ
observation with an accumulated beam intensity corresponding to 7.5 MW·year [3]. For these purposes, prompt realization of the designed beam power is vitally important, and an upgrade to the
Mega-Watt beam will directly enhance the reach of the future project.
The J-PARC accelerator cascade consists of a normal-conducting Linac as an injection system, a
Rapid Cycling Synchrotron (RCS), and a Main Ring synchrotron (MR). H− ion beams, with a peak
current of 50 mA and pulse width of 500 µs, are accelerated to 400 MeV by the Linac. Conversion
into a proton beam is achieved by charge-stripping foils at injection into the RCS, which accumulates
and accelerates two beam bunches up to 3 GeV at a repetition rate of 25 Hz. Most of the bunches are
extracted to the Materials and Life Science Facility (MLF) and used to generate intense neutron/muon
beams. The RCS extraction beam power is rated at 1 MW. With a prescribed repetition cycle, four
successive beam pulses are injected from the RCS into the MR to form eight bunches in a cycle
and accelerated up to 30 GeV. In the fast extraction mode, the circulating proton beam bunches are
extracted to the neutrino primary beam-line within a single turn by a kicker/septum magnet system.
Fig. 1 shows the layout of the neutrino experimental facility. The primary beam-line guides the
extracted proton beam to a production target/pion-focusing horn system at a target station (TS). The
Neutron Time-Of-Flight Spectrometer Based on HIRFL for Studies of
Spallation Reactions Related to ADS Project
ZHANG Suyalatu1,2 , CHEN Zhiqiang1,*, HAN Rui 1 , WADA Roy1 , LIU Xingquan 1,2 , LIN
Weiping1,2 , LIU Jianli 1 , SHI Fudong1 , REN Peipei 1,2 , TIAN Guoyu 1,2 , LUO Fei 1
1
Institute of Modern Physics, Chinese Academy of Sciences, Gansu, Lanzhou 730000, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
*
Corresponding author. E-mail address: zqchen@impcas.ac.cn
Abstract: A Neutron Time-Of-Flight (NTOF) spectrometer based on Heavy Ion Research Facility in
Lanzhou (HIRFL) is developed for studies of neutron production of proton induced spallation
reactions related to the ADS project. After the presentation of comparisons between calculated
spallation neutron production double-differential cross sections and the available experimental one, a
detailed description of NTOF spectrometer is given. Test beam results show that the spectrometer
works well and data analysis procedures are established. The comparisons of the test beam neutron
spectra with those of GEANT4 simulations are presented.
Key words: Time-Of-Flight spectrometer, Neutron production cross section, Spallation reaction,
ADS project, GEANT4
I.
Introduction
A great interest of spallation reactions
[1,2]
has been increasing with the development of
Accelerator Driven Systems (ADS) and the applications of Spallation Neutron Source (SNS). The
spallation reaction is defined as interactions between a light projectile (e.g. proton) with the GeV
range energy and heavy target nuclei which is split to a large number of hadrons (mostly neutrons)
or fragments. Many nuclear models, such as intra-nuclear cascade-evaporation (INC/E)
and quantum molecular dynamics (QMD) model
[4]
[3]
model
, have been developed to study spallation
reactions. These nuclear models are coded for thin-target simulations. In order to perform
calculations for practical applications, which may involve complex geometries and multiple
composite materials, nuclear models need to be embedded into a sophisticated transport code. The
combination of nuclear models with a Monte Carlo transportation code like MCNP [5], GEANT4 [6,7]
and FLUKA
[8,9]
, nucleon meson transport codes (NMTC)
facilities of engineering applications of the spallation reaction.
[10]
are widely utilized for designing
tat
io
Pa nal T
rti he
cle or
Ph etic
ysi al
cs
B
Co
m
pu
AC
KA
SFB TR9
DESY 14-159, DO–TH 14/22, SFB/CPP–14–73 , LPN 14–113
Higher Order Heavy Quark Corrections to Deep-Inelastic Scattering
J. Bl¨umleina , A. De Freitasa,b , and C. Schneiderb
arXiv:1411.5669v1 [hep-ph] 20 Nov 2014
a Deutsches
b Research
Elektronen-Synchrotron, DESY, Platanenallee 6, D-15738 Zeuthen, Germany
Institute for Symbolic Computation (RISC), Johannes Kepler University, Altenbergerstraße 69, A-4040 Linz, Austria
Abstract
The 3-loop heavy flavor corrections to deep-inelastic scattering are essential for consistent next-to-next-to-leading
order QCD analyses. We report on the present status of the calculation of these corrections at large virtualities Q2 . We
also describe a series of mathematical, computer-algebraic and combinatorial methods and special function spaces,
needed to perform these calculations. Finally, we briefly discuss the status of measuring α s (MZ ), the charm quark
mass mc , and the parton distribution functions at next-to-next-to-leading order from the world precision data on deepinelastic scattering.
Keywords: Deep-inelastic scattering, strong coupling constant, heavy flavor corrections, charm quark mass,
mathematical structures
1. Introduction
Deep-inelastic scattering (DIS) provides an important
method to determine the distribution function of the
partons inside nucleons and to measure the strong coupling constant α s from the scaling violations of the nucleon structure functions. Their heavy flavor corrections also allow the determination of the charm quark
mass mc . Currently the world data on DIS have reached
a precision which needs the next-to-next-to-leading order (NNLO) QCD corrections for an adequate description of the data. While the massless 3-loop corrections are known [1–4], the heavy flavor Wilson coefficients are only known to next-to-leading order [5]1 .
Currently the NNLO corrections to the heavy flavor
Wilson coefficients are being calculated. In this survey we give a detailed account on this project, including technical aspects of the computation, such as systematic analytic summation and integration techniques,
and their computer-algebraic implementation. On very
1 For
a numerical implementation in Mellin space see [6].
general grounds, Feynman integrals may be turned into
nested sums [7, 8]. In this context also new mathematical function spaces and algebras are of importance,
which have been worked out along with the current
project. We also give a brief account on these structures2 . Finally, we present recent phenomenological
applications determining the twist-2 parton distribution
functions at NNLO in the unpolarized case and at NLO
in the polarized case and measuring the strong coupling constant α s (MZ2 ) and the charm quark mass mc
from the world deep-inelastic scattering data. This survey summarizes main results of the research performed
in project B3:‘Structure functions in the continuum’ of
DFG Sonderforschungsbereich Transregio 9, Computergest¨utzte Theoretische Teilchenphysik. Related studies using lattice gauge methods are given in [11].
The deep-inelastic scattering cross section is of the
form
d2 σ
∼ Lµν Wµν ,
dxdQ2
2 For
recent reviews see [9, 10].
(1)
Pion-pion cross section from proton-proton collisions at the LHC
B. Z. Kopeliovich, I. K. Potashnikova, and Iv´an Schmidt
1
Departamento de F´ısica, Universidad T´ecnica Federico Santa Mar´ıa; and
Centro Cient´ıfico-Tecnol´
ogico de Valpara´ıso; Casilla 110-V, Valpara´ıso, Chile
H. J. Pirner1 and K. Reygers2
arXiv:1411.5602v1 [hep-ph] 20 Nov 2014
1
Institute for Theoretical Physics, University of Heidelberg, Germany
2
Physikalisches Institut, University of Heidelberg, Germany
The pion-pion total cross section at high energies, unknown from data, can be extracted from
proton-proton collisions with production of forward-backward leading neutrons, pp → n X n. The
zero-degree calorimeters (ZDC) installed in the ALICE, ATLAS, and CMS experiments at the LHC,
make such a measurement possible. One can also access elastic ππ scattering measuring the exclusive
two-pion production channel, pp → n π + π + n. An analysis aimed at extraction of the pion-pion
cross section from data is strongly affected by absorptive corrections, which can also be treated as
a survival of rapidity gaps. The study of absorption effects is the main focus of the present paper.
These effects are studied on the amplitude level and found to be different between the pion flux,
which conserves the nucleon helicity, and the one which flips helicity. Both fluxes are essentially
reduced by absorption, moreover, there is a common absorption suppression factor, which breaks
down the factorized form of the cross section. We also evaluated the contribution of other iso-vector
Reggeons, ρ, a2 and a1 .
PACS numbers: 13.85.Dz, 13.85.Lg, 13.85.Ni, 14.20.Dh
I.
INTRODUCTION
The proton-proton elastic scattering cross section has
been measured in a wide range of energies,
and recently
√
up to the highest energy of the LHC, s = 7 TeV [1, 2].
At the same time, measurements of the pion-nucleon
cross section have been
√ restricted so far to rather low
energies, up to about s = 35 GeV [3]. The pion-pion
cross section cannot be measured directly, and has been
extracted from data only at very low energies near threshold [4]. The theoretical description of elastic scattering
has been based so far only on phenomenological models.
Even the simplest versions of Regge models, assuming
Pomeron pole dominance (no cuts) [5] still describe the
available data reasonably well, in spite of the obvious
problems with the unitarity bound at higher energies.
Among the unitarized models [6–11], a precise prediction of the elastic cross section at the LHC was done in
[12, 13]. In contrast to the models treating teh Pomeron
as a simple Regge pole, an increasing rate of the energy
dependence was predicted. Even a steeper rise of the
cross sections at high energies is expected for π-p and
π-π scattering. The models [14] based on non perturbative interaction dynamics fixed at low energies, predict
an increasing cross section with energy. These models
provided predictions for pp, πp and ππ cross sections.
The possibility of having a pion-pion collider does not
seem to be realistic, and it has not been seriously considered so far. However, one can make use of virtual
pion beams. Indeed, nucleons are known to have pion
clouds, with low virtuality, so high energy proton beams
are accompanied by an intensive flux of high-energy pions, which participate in collisions. This way to measure
electron-pion collisions was employed in the ZEUS [15]
and H1 [16] experiments at HERA. Pion contribution
was singled out by detecting leading neutrons with large
fractional momentum, z. The main objective of these
measurements was the determination of the pion structure function F2π (x, Q2 ) at low x. This task turned out
to be not straightforward, because of absorptive corrections, which suppress the cross section. In fact, recent
study of these effects [24] found them to be quite strong,
reducing significantly the cross section. A good description of data was achieved. A weaker effect of absorption
was expected in Refs. [17–20].
Detecting leading neutrons with large z in pp collisions one can access the π-p total cross section at energies much higher than with real pion beams. Apparently,
the absorptive corrections in this case should be similar
or stronger than in γ ∗ -p collisions. A detailed study of
these effects was performed in [25]. However, no data
from modern colliders have been available so far, except
for a few points with large error bars from the PHENIX
experiment [21, 22] and old data from ISR [23]. The
normalization of the latter was found unreliable in [25].
Earlier attempts to extract the ππ and πp cross sections from neutron production at low energies of fixed
target experiments were made in [26, 27], although no
absorptive corrections were introduced.
The experiments ATLAS, CMS and ALICE at the
LHC, are equipped with zero-degree calorimeters, which
are able to detect neutrons at very small angles. This
is ideal for experimenting with pions accompanying the
colliding protons. In particular, detecting leading neutrons, simultaneously produced in both directions, one
can accesses pion-pion collisions at high c.m. energy,
sππ = (1 − z1 )(1 − z2 )s, where z1,2 are the fractional momenta of the detected neutrons. Naturally, this process is
arXiv:1411.5539v1 [hep-ph] 20 Nov 2014
Chiral phase transition in an extended linear sigma model:
initial results ∗
´ cs
Gy. Wolf, P. Kova
Institute for Particle and Nuclear Physics, Wigner Research Center for Physics,
Hungarian Academy of Sciences, POB 49, H-1525 Budapest, Hungary
´p
Zs. Sze
MTA-ELTE Statistical and Biological Physics Research Group, H-1117 Budapest,
Hungary
We investigate the scalar meson mass dependence on the chiral phase
transition in the framework of an SU(3), (axial)vector meson extended linear sigma model with additional constituent quarks and Polyakov loops.
We determine the parameters of the Lagrangian at zero temperature in a
hybrid approach, where we treat the mesons at tree-level, while the constituent quarks at 1-loop level. We assume two nonzero scalar condensates
and together with the Polyakov-loop variables we determine their temperature dependence according to the 1-loop level field equations.
PACS numbers: 12.39.Fe,12.40.Yx, 14.40.Be, 14.40.Df, 21.65.Qr, 25.75.Nq
1. Introduction
The investigation of the QCD phase diagram is a very important subject
both theoretically and experimentally nowadays. The ongoing and future
heavy ion experiments such as RHIC, and CERN/LHC study the low density
part of the phase diagram which can also be investigated theoretically by
lattice QCD, at CBM/FAIR the high density part will be studied, which is
still not settled theoretically, so it is worth to investigate the phase diagram
thoroughly.
Our starting point is the (axial)vector meson extended linear sigma
model with additional constituent quarks and Polyakov-loop variables. The
∗
Presented
at
the
Workshop
on
Unquenched
Hadron
Non-Perturbative Models and Methods of QCD vs.
At the occasion of Eef van Beveren’s 70th birthday
(1)
Spectroscopy:
Experiment,
arXiv:1411.5528v1 [physics.data-an] 20 Nov 2014
Preprint typeset in JINST style - HYPER VERSION
Kernel density estimation of a multidimensional
efficiency profile
Anton Poluektova,b
a
University of Warwick,
Gibbet Hill Road, Coventry, CV4 7AL, UK
a Budker Institute of Nuclear Physics,
630090, Lavrentieva 11, Novosibirsk, Russia
E-mail: Anton.Poluektov@cern.ch
A BSTRACT: Kernel density estimation is a convenient way to estimate the probability density of
a distribution given the sample of data points. However, it has certain drawbacks: proper description of the density using narrow kernels needs large data samples, whereas if the kernel width is
large, boundaries and narrow structures tend to be smeared. Here, an approach to correct for such
effects, is proposed that uses an approximate density to describe narrow structures and boundaries. The approach is shown to be well suited for the description of the efficiency shape over a
multidimensional phase space in a typical particle physics analysis. An example is given for the
five-dimensional phase space of the Λb0 → D0 pπ − decay.
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP/2014-249
2014/11/21
CMS-TOP-13-010
arXiv:1411.5621v1 [hep-ex] 20 Nov 2014
Measurement of the cross section ratio σttbb /σttjj in pp
√
collisions at s = 8 TeV
The CMS Collaboration∗
Abstract
The first measurement of the cross section ratio σttbb /σttjj is presented using a data
sample corresponding
to an integrated luminosity of 19.6 fb−1 collected in pp colli√
sions at s = 8 TeV with the CMS detector at the LHC. Events with two leptons (e
or µ) and four reconstructed jets, including two identified as b quark jets, in the final
state are selected. The ratio is determined for a minimum jet transverse momentum
pT of both 20 and 40 GeV/c. The measured ratio is 0.022 ± 0.003 (stat) ± 0.005 (syst)
for pT > 20 GeV/c. The absolute cross sections σttbb and σttjj are also measured. The
measured ratio for pT > 40 GeV/c is compatible with a theoretical quantum chromodynamics calculation at next-to-leading order.
Submitted to Physics Letters B
c 2014 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license
∗ See
Appendix A for the list of collaboration members
Higgs Measurement at e+e- Circular Colliders
Manqi RUANa, b
b
a
CERN, 40-b1-06, Geneva, Switzerland
Institute of High Energy Physics, 19 B Yuquan Road, Beijing, China
Abstract
Now that the mass of the Higgs boson is known, circular electron positron colliders, able to measure the
properties of these particles with high accuracy, are receiving considerable attention. Design studies have been
launched (i) at CERN with the Future Circular Colliders (FCC), of which an e+e- collider is a potential first step
(FCC-ee, formerly caller TLEP) and (ii) in China with the Circular Electron Positron Collider (CEPC). Hosted in a
tunnel of at least 50 km (CEPC) or 80-100 km (FCC), both projects can deliver very high luminosity from the Z
peak to HZ threshold (CEPC) and even to the top pair threshold and above (FCC-ee).
At the ZH production optimum, around 240 GeV, the FCC-ee (CEPC) will be able to deliver 10 (5) ab-1
integrated luminosity in 5 (10) years with 4 (2) interaction points: hence to produce millions of Higgs bosons
through the Higgsstrahlung process and vector boson fusion processes. This sample opens the possibility of subper-cent precision absolute measurements of the Higgs boson couplings to fermions and to gauge-bosons, and of
the Higgs boson width. These precision measurements are potentially sensitive to multi-TeV range new physics
interacting with the scalar sector. The ZH production mechanism also gives access to the invisible or exotic
branching ratios down to the per mil level, and with a more limited precision to the triple Higgs coupling. For the
FCC-ee, the luminosity expected at the top pair production threshold (√s ~ 340-350 GeV) further improves some
of these accuracies significantly, and is sensitive to the Higgs boson coupling to the top quark.
Keywords: Higgs factory, Circular Collider, FCC-ee, CEPC
1. Introduction
The Higgs boson is not only the last found piece of
the Standard Model (SM) [1, 2], but also an extremely
strange object. It is the only scalar particle in the SM,
and it is also responsible for most of the SM
theoretical difficulties and defects. The Higgs boson
might be a portal leads to more profound physics
models and even physics principles. Therefore, a
Higgs factory that can precisely determine the
properties of the Higgs boson is an important future
step in the high-energy physics exploration.
The LHC itself is already a Higgs factory. It not
only discovered the Higgs boson, but also
demonstrated that the discovered Higgs boson is
highly likely to be the one predicted by the SM. The
future HL-LHC program will, with 2 orders of
magnitude higher integrated luminosity, highly
enhance the understanding of this mysterious boson.
Higgs measurement at a proton collider is limited
by the Higgs width measurements. The natural width
of a 125 GeV Higgs boson is only 4.2 MeV, while the
best precision achieved with current LHC data is of
o(10) MeV [3]. The Higgs width measurement is an
essential ingredient to determine the partial width and
then the coupling constants. On the contrary, the
electron-positron collider has a remarkable capability
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
sin2 θeff and MW (indirect) extracted from 9 fb−1 µ+ µ− event sample at CDF
lept
A. Bodek, on behalf of the CDF Collaboration
arXiv:1411.5549v1 [hep-ex] 20 Nov 2014
Department of Physics and Astronomy, University of Rochester, Rochester, NY. 14627, USA
To be published in the proceedings of the 37th International Conference on High-Energy Physics, ICHEP 2014
FERMILAB-CONF-14-355-E, CDF Note 11129
Abstract
lept
We report on the extraction of sin2 θeff and indirect measurement of the mass of the W boson from the forwardbackward asymmetry of µ+ µ− events in the Z boson mass region. The data sample collected by the CDF detector
lept
corresponds to the full 9 fb−1 run II sample. We measure sin2 θeff = 0.2315 ± 0.0010, sin2 θW = 0.2233 ± 0.0009 and
MW (indirect) = 80.365±0.047 GeV/c2 , where each uncertainty includes both statistical and systematic contributions.
Comparison with the results of the D0 collaboration is presented.
Keywords: Electroweak Mixing Angle
1. Introduction
Now that the Higgs mass is known, the Standard
Model is over constrained. Therefore, any inconsistency
between precise measurements of SM parameters would
be indicative of new physics. The parameter that needs
to be measured more precisely is MW (with errors <15
2
MeV), or equivalently sin2 θW = 1 − MW
/MZ2 (with errors <0.0003). Similarly, in order to help resolve the
lept
long standing 3σ difference in sin2 θeff (MZ ) between
lept
SLD and LEP, new measurements of sin2 θeff (MZ )
should have errors similar to SLD or LEP (±0.0003).
lept
sin2 θeff (LEP − 1 : Z pole) = 0.23221 ± 0.00029
lept
sin2 θeff (S LD : Z pole)
= 0.23098 ± 0.00026
lept
sin2 θeff and
Precise extractions of
sin2 θW = 1 −
2
MW
/MZ2 using the forward-backward asymmetry (Afb )
of dilepton events produced in p p¯ and pp collisions are
now possible for the first time because of three new innovations:
• A new technique [1] for calibrating the muon energy scale as a function of detector η and φ (and
sign), thus greatly reducing systematic errors from
the energy scale. A similar method can also used
for electrons.
• A new event weighting technique[3]. With this
technique all experimental uncertainties in acceptance and efficiencies cancel (by measuring the
cos θ coefficient A4 and using the relation AFB =
8A4 /3). Similarly, additional weights can be included for antiquark dilution, which makes the
analysis independent of the acceptance in dilepton
rapidity.
• The implementation[2] of Z fitter Effective Born
Approximation (EBA) electroweak radiative corrections into the theory predictions of POWHEG
and RESBOS which allows for a measurement of
lept
2
both sin2 θeff (MZ ) and sin2 θW = 1 − MW
/MZ2 .
1.1. Momentum-energy scale corrections
This new technique[1] is used in CDF (for both
muons and electrons) and also in CMS. In CMS it is
used to get a precise measurement of the Higgs mass in
the four lepton channel. The technique relies on the fact
that the Z boson mass is well known as follows:
arXiv:1411.5529v1 [hep-ex] 20 Nov 2014
First Measurements of Spin Correlation Using
Semi-leptonic tt¯ Events at ATLAS
Boris Lemmer
On behalf of the ATLAS Collaboration
II. Physikalisches Institut, Georg-August-Universit¨
at G¨
ottingen
E-mail: boris.lemmer@cern.ch
Abstract. The top quark decays before it hadronizes. Before its spin state can be changed
in a process of strong interaction, it is directly transferred to the top quark decay products.
The top quark spin can be deduced by studying angular distributions of the decay products.
The Standard Model predicts the top/anti-top quark (tt¯) pairs to have correlated spins. The
degree is sensitive to the top-quark spin itself and the production mechanisms of the top quark.
Measuring the spin correlation allows to test the predictions. New physics effects can be reflected
in deviations from the prediction. The measurement of the spin correlation of tt¯ pairs, produced
√
at the LHC with a center-of-mass energy of s = 7 TeV and reconstructed with the ATLAS
detector, is presented. The dataset corresponds to an integrated luminosity of 4.6 fb−1 . tt¯ pairs
are reconstructed in the `+jets channel using a kinematic likelihood fit offering the identification
of light up- and down-type quarks from the t → bW → bq q¯0 decay. The spin correlation is
measured via the distribution of the azimuthal angle ∆φ between two top quark spin analyzers
in the laboratory frame. It is expressed as the degree of tt¯ spin correlation predicted by the
Standard Model, f SM . The result of f SM = 1.12 ± 0.11 (stat.) ± 0.22 (syst.) is consistent with
the Standard Model prediction of f SM = 1.0.
1. Spin Correlation in tt¯ Pairs
−25 s
The top quark as heaviest of all known quarks decays with a lifetime of 3.29+0.90
−0.63 · 10
[1]. This is at least one order of magnitude shorter than the timescale of hadronization and
depolarization and allows to deduce the top quark’s spin information via the measurement of
angular distributions of its decay products [2, 3]. Within the Standard Model (SM), top quarks
are produced almost unpolarized via the strong interaction. However, when being produced in
pairs their spins are predicted to be correlated. The degree of observed correlation depends
on the production and decay mechanisms of tt¯ pairs. Deviations from the SM prediction can
give hints for physics beyond the Standard Model, like the production via a high-mass Z 0 boson
[4, 5], a heavy Higgs boson [6] or the decay of a top quark into a bottom quark and a charged
Higgs boson [7, 8].
tt¯ spin correlations have been measured by the CDF and D0 collaborations using angular
distributions of the tt¯ decay products [9, 10]. The D0 collaboration reported a first evidence
for non-vanishing spin correlation using a matrix-element approach in the ` + jets channel [11].
At the LHC [12] the CMS collaboration measured the tt¯ spin correlation using the difference
of azimuthal angles between the two charged leptons in the laboratory frame, ∆φ, in dileptonic
tt¯ events [13]. This observable is sensitive to tt¯ spin correlation arising from gluon fusion
arXiv:1411.5671v1 [hep-th] 20 Nov 2014
Inflation, de Sitter Landscape and Super-Higgs effect
Renata Kallosh,1 Andrei Linde1 and Marco Scalisi1,2
1
2
SITP and Department of Physics, Stanford University, Stanford, CA 94305 USA
Van Swinderen Institute for Particle Physics and Gravity, University of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands
Abstract
We continue developing models which provide a simple unified description of inflation and
the current acceleration of the universe in the supergravity context. We describe here a general
class of models with a positive cosmological constant at the minimum of the potential, such that
supersymmetry is spontaneously broken in the direction of the nilpotent superfield S. In the unitary
gauge, these models have a simple action where all highly non-linear fermionic terms of the classical
Volkov-Akulov action disappear. We present masses for bosons and fermions in these theories.
EPJ manuscript No.
(will be inserted by the editor)
Confinement and screening in tachyonic matter
F.A. Brito1 , M.L.F. Freire2 , W. Serafim1,3 ,
1
Departamento de F´ısica, Universidade Federal de Campina Grande, 58109-970 Campina Grande, Para´ıba, Brazil
Departamento de F´ısica, Universidade Estadual da Para´ıba, 58109-753 Campina Grande, Para´ıba, Brazil
3
Instituto de F´ısica, Universidade Federal de Alagoas, 57072-970 Macei´
o, Alagoas, Brazil
arXiv:1411.5656v1 [hep-th] 20 Nov 2014
2
Abstract. In this paper we consider confinement and screening of the electric field. We study the behavior
of a static electric field coupled to a dielectric function with the intent of obtaining an electrical confinement
similar to what happens with the field of gluons that bind quarks in hadronic matter. For this we use the
phenomenon of ‘anti-screening’ in a medium with exotic dielectric. We show that tachyon matter behaves
like an exotic way whose associated dielectric function modifies the Maxwell’s equations and affects the
fields which results in confining and Coulombian-like potentials in three spatial dimensions. We note that
the confining regime coincides with the tachyon condensation, which resembles the effect of confinement
due to condensation of magnetic monopoles. The Coulombian-like regime is developed at large distance
which is associated with a screening phase.
Introduction
The confinement arises naturally in QCD (Quantum Chromodynamics) where the fields of gluons and quarks appear
in a confined state at low energies. Similarly to the electric field, we associate the gluon field charges to “color
charges”. In our studies we show that in general the confining phenomenon can be considered as an effect of a dielectric on the fields and charges with the opposite effect
of the screening “called anti- screening”. Throughout the
paper we shall mention the anti-screening as the way how
electric field behaves in a medium with asymptotic behavior that is opposite to that well-known asymptotic behavior in a usual dielectric medium. The hadron matter in
its confining phase develops this behavior. The tachyonic
field is presented here as a good way to develop both antiscreening (the confinement regime) and screening behavior (the Coulomb-potential behavior at sufficiently large
interquark separation). This seems to be the way in which
the hadronic matter lives. In three spatial dimensions this
effect presents Coulomb and confinement potentials to describe the potential between quark pairs. Normally it is
used the potential of Cornell [1] vc (r) = − ar + br, where
a and b are positive constants, and r is the distance between heavy quarks. In QED (Quantum Electrodynamics),
the effective electrical charge increases when the distance
r between a pair of electron-anti-electron decreases. On
the other hand, in QCD there is an effect that creates
a color charge which decreases as the distance between
a pair of quark and anti-quark decreases. Thus, in this
sense, the QCD develops effectively opposite QED phenomena. So it is natural to try to understand the QCD
phenomena in terms of QED in an “exotic” medium such
that it creates an anti - screening effect at some regime
near the QCD scale. In these sense we assume that the
electric field is now modified by a “dielectric function”.
′
q
≡ G(r)r
Consider E(r) ≡ q r(r)
2
2 where E(r) represents the
field due to an electric charge q immersed in a polarizable
medium playing the role of a “color” charge coupled to
a dielectric function G(r) where r is the distance of the
screening (or anti-screening ). The performance of screening in the QED is expressed according to the effective
electrical charge i.e., q ′ (r ≫ d) ≤ 1 or G(r ≫ d) ≥ 1
and q ′ (r ≪ d) > 1 or G(r ≪ d) < 1 being d the typical
size of the screening produced by the polarization of the
molecules. On the other hand, in QCD the phenomenon of
anti-screening manifests with color charge q ′ (r ≫ R) ≫ 1
or G(r ≫ R) ≪ 1 and q ′ (r < R) → 1 or G(r < R) → 1
and R is the radius of the anti-screening which is the typical size of hadrons. Since we are interested in confinement
we will focus our interest in the latter case where the dielectric function G(r) is such that the anti-screening provides the QCD color confinement in a pair of heavy quark.
Despite of this, in our present study, a dynamical G(r)
comes out in the tachyonic matter, such that for sufficiently large distance the anti-screening breaks down and
a screening phase associated with hadronization (or light
quarks pair creation) takes place. Indeed the main propose in the present study is to define a potential model
that may develop appropriate potentials for the confining
and screening regimes. Whereas the Cornell potential is
good to describe heavy quarks, for light quarks a screening regime takes place for sufficiently large interquark separation and another appropriate potential is necessary. In
our set up the tachyon matter properly develops the de-
Jet transport and photon bremsstrahlung via longitudinal and transverse scattering
Guang-You Qin1, 2 and Abhijit Majumder2
arXiv:1411.5642v1 [nucl-th] 20 Nov 2014
1
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE),
Central China Normal University, Wuhan, 430079, China
2
Department of Physics and Astronomy, Wayne State University, Detroit, MI, 48201.
(Dated: November 21, 2014)
We study the effect of multiple scatterings on the propagation of hard partons and the production
of jet-bremsstrahlung photons inside a dense medium in the framework of deep-inelastic scattering
off a large nucleus. We include the momentum exchanges in both longitudinal and transverse
directions between the hard partons and the constituents of the medium. Keeping up to the second
order in a momentum gradient expansion, we derive the spectrum for the photon emission from
a hard quark jet when traversing dense nuclear matter. Our calculation demonstrates that the
photon bremsstrahlung process is influenced not only by the transverse momentum diffusion of the
propagating hard parton, but also by the longitudinal drag and diffusion of the parton momentum.
A notable outcome is that the longitudinal drag tends to reduce the amount of stimulated emission
from the hard parton.
I.
INTRODUCTION
The modification of hard partonic jets in dense media provides a useful tool for studying the properties of
the highly excited nuclear matter produced in relativistic heavy-ion collisions. One of the primary experimental
signatures for jet modification is the significant depletion
of the high transverse momentum (pT ) hadron yield in
heavy-ion collisions compared to that in binary-scaled
proton-proton collisions [1–3]. Such depletion has been
attributed to the loss of the forward momentum and energy by the hard partons in the dense nuclear medium
they traversed before fragmenting into hadrons [4, 5].
By all account, one expects the energy loss to originate from a combination of elastic collisions [6–10] and
inelastic radiative processes [4, 5, 11–13] that hard jets
experience when propagating through the dense media.
For the light partons, the medium-induced gluon radiation is thought to be the more dominant mechanism for
the parton energy loss. For heavy flavor partons with
large finite masses, collisional energy loss appears to be
equally or even more important than medium-induced
gluon radiation, especially at low and intermediate pT
regime [14–18].
There are currently a few different schemes for the
study of medium-induced gluon bremsstrahlung and
radiative part of parton energy loss in dense nuclear medium, namely, Baier-Dokshitzer-Mueller-PeigneSchiff-Zakharov (BDMPS-Z) [11–13], Gyulassy, Levai
and Vitev (GLV) [19–21], Amesto-Salgado-Wiedemann
(ASW) [22, 23], Arnold-Moore-Yaffe (AMY) [24, 25] and
higher twist (HT) [26–28] formalisms. More detailed
comparison of different formalisms may be found in Ref.
[29]. Sophisticated phenomenological have been performed for various jet quenching observables, such as
single inclusive hadron suppression [30–32], as well as dihadron and photon-hadron correlations [33–36]. One of
the main goals of these studies is to quantitatively extract
the jet transport parameters, such as qˆ and eˆ, in dense
media by comparing with the data on jet modification.
This requires that the overarching formalisms contain a
representative description of all physical processes that
influence the partonic substructure of the jet.
While different parton energy loss models mentioned
above have rather different origins and make slightly different approximations, the calculations of radiative energy loss have so far only focused on the gluon radiation
induced by transverse momentum diffusion experienced
by the propagating hard partons in the dense medium. In
fact, when a jet scatters off the medium constituents, it is
not only the transverse momentum, but also the longitudinal momentum that are exchanged between the jet and
the medium [37–39]. In many calculations, the transfer of
longitudinal momentum has only been considered in the
evaluation of purely collisional energy loss. There have
been studies on the longitudinal momentum loss experienced by radiated partons in the context of jet shower
evolution [40–43]. However, the influence of exchanging longitudinal momentum on the stimulated radiation
vertex has not yet been considered. In this work, we reinvestigate the medium-induced radiation, by taking into
account the influence from both transverse and longitudinal momentum transfers when jets undergo multiple
scatterings with the medium in the radiation process.
As a step up to more complicated calculation of gluon
radiation, we study the problem of real photon radiation
from a partonic jet which propagates through a dense
medium and experiences multiple scatterings of gluons.
While the emitted photon escapes the medium without
further strong-interaction with medium, very unlike the
case of a radiated gluon, such a problem does encode
many interesting features of the medium-induced gluon
radiation, such as the Landau-Pomeranchuck-Migidal
(LPM) effect, as well as the approximation schemes involved in the problem, which are the same as the problem
with gluon radiation. Therefore, the photon calculation
serves as an intermediate step for the further investigation of medium-induced gluon emission from a hard jet.
In addition, photon bremsstrahlung from a high pT
jet is itself of great interest. Such process has shown
November 21, 2014
Lattice QCD Study of B-meson Decay Constants from ETMC
A. Bussone a , N. Carrasco b , P. Dimopoulos c,d , R. Frezzotti c , V. Gim´
enez e ,
G. Herdo´ıza f , P. Lami b,g , V. Lubicz b,g , C. Michael h , E. Picca b,g , L. Riggio b ,
G.C. Rossi c,d , F. Sanfilippo i , A. Shindler j , S. Simula b , C. Tarantino b,g
arXiv:1411.5566v1 [hep-lat] 20 Nov 2014
ETM Collaboration
a CP 3 -Origins
& Danish IAS, University of Southern Denmark, Odense M, Denmark
b INFN,
Sezione di Roma Tre, Rome, Italy
c Dipartimento
di Fisica, Universit`
a di Roma “Tor Vergata”,
INFN, Sezione di Tor Vergata, Rome, Italy
d Museo
Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Rome, Italy
e Departament
f Instituto
de F´ısica Te`
orica and IFIC, Univ. de Val`encia-CSIC, Val`encia, Spain
de F´ısica Te´
orica UAM/CSIC and Departamento de F´ısica Te´
orica,
Universidad Aut´
onoma de Madrid, Madrid, Spain
g Dipartimento
di Matematica e Fisica, Universit`
a degli Studi Roma Tre, Rome, Italy
h Theoretical
i School
j IAS,
Physics Division, The University of Liverpool, Liverpool, UK
of Physics and Astronomy, University of Southampton, Southampton, UK
IKP, JCHP and JARA-HPC, Forschungszentrum J¨
ulich, J¨
ulich, Germany
We discuss a lattice QCD computation of the B-meson decay constants by
the ETM collaboration where suitable ratios allow to reach the bottom quark
sector by combining simulations around the charm-quark mass with an exactly
known static limit. The different steps involved in this ratio method are discussed
together with an account of the assessment of various systematic effects. A
comparison of results from simulations with two and four flavour dynamical
quarks is presented.
PRESENTED AT
8th International Workshop on the CKM
Unitarity Triangle (CKM 2014)
Vienna, Austria, September 8-12, 2014
1
Introduction
Flavour physics is the place of election where probing the scale of possible extensions of
the Standard Model (SM) can be carried out up to energies considerably larger than the
ones that can be attained in present-day colliders such as the LHC. A detailed comparison
of experimental results to theoretical expectations based solely on the SM is essential to
determine its fundamental parameters. The study of the consistency of the determinations
of SM parameters by using as many independent processes as possible provides a very
stringent test of the theory in its present formulation. For this program to be successful
non-perturbative QCD effects contributing to flavour physics processes must be accurately
evaluated. In particular lattice QCD studies of hadronic matrix elements of weak operators
are essential to test unitarity constraints in the first two rows of the CKM matrix.
Leptonic decays of B-mesons, B → τ ν, have been thoroughly studied at the B-factories.
A reduction in the relative error on the branching fraction, from ∼ 20% to ∼ 5%, is expected
to be reached by Belle-II. An improvement in the extraction of the CKM matrix element
|Vub | would thus also profit from a more accurate lattice calculation of the B-meson decay
constant, fB . Similarly, rare leptonic decays of neutral B-mesons are being studied by LHC
experiments. CMS and LHCb have measured the branching fraction, B(Bs → µ+ µ− ), with
a ∼ 25% relative precision. In this case, the lattice determinations of the Bs -meson decay
constant, fBs , is an important ingredient in the SM prediction of this branching fraction.
The study of the b-quark sector on the lattice requires the development of a dedicated
approach. The reason is that the b-quark mass, mb ∼ 4.2 GeV, is larger than the range of
values of the UV cutoff – given by the inverse of the lattice spacing a – that can currently
be probed in large-volume lattice QCD simulations, a−1 . 4 GeV. The condition, amb 1,
needed to guarantee the convergence of an expansion in powers of the lattice spacing is
therefore not fulfilled. This leads to uncontrolled systematic effects due to lattice artefacts.
Several methods, relying to some extent on the use of effective theories, have been developed
to address these difficulties (see Ref. [1] for a recent review of the various approaches).
In the following we will discuss the results of the determination of the B-meson decay
constants with a method that is based on the construction – directly in QCD – of ratios of
observables that are well behaved from the point of view of lattice artefacts and that have
a precisely known static limit.
2
Approaching the b-quark sector through the ratio method
To illustrate the ratio method [2], let us consider an observable, Ξ(mh ), depending on the
heavy quark mass mh according to the scaling laws of heavy quark effective theory (HQET),
d1
1
Ξ(mh ) = Ξstat +
,
(1)
+ O
mh
m2h
where Ξstat refers to√the observable in the static limit, mh → ∞. A well known example is,
Ξ(mh ) = Φh` = fh` Mh` , where fh` and Mh` are the heavy-light (h`) pseudoscalar meson
decay constant and mass, respectively, depending on mh . By considering a geometric series
1
Quantum correlations in two-flavour neutrino oscillations
Ashutosh Kumar Alok,1, ∗ Subhashish Banerjee,1, † and S. Uma Sankar2, ‡
1
2
Indian Institute of Technology Jodhpur, Jodhpur 342011, India
Indian Institute of Technology Bombay, Mumbai 400076, India
(Dated: November 21, 2014)
arXiv:1411.5536v1 [quant-ph] 20 Nov 2014
Neutrino oscillations provide evidence for the mode entanglement of neutrino mass eigenstates in
a given flavour eigenstate. Given this mode entanglement, it is pertinent to ask if other quantum
correlations are present in neutrino evolution. In this study, we compute a number of such correlations for accelerator neutrinos in the approximation of two flavour νµ ↔ ντ oscillations. The point
of minimum survival probability corresponds to the extremum point of all measures of quantum
correlations. We find that Bell’s inequality is always violated.
I.
INTRODUCTION
The foundations of quantum mechanics are usually
studied in optical or electronic systems. In such systems,
the interplay between the various measures of quantum
correlations is well known. Due to the technical advances
in high energy physics experiments, in particular the meson factories and the long baseline neutrino experiments,
it will be fruitful to test the foundations of quantum mechanics in such systems.
In [1], the interplay between various measures of quantum correlations were studied, for the first time, in the
context of correlated unstable neutral meson systems. It
was observed that the quantum correlations for these unstable systems can be non-trivially different from their
stable counterparts. We now turn our attention to neutrinos, where such an interplay has not yet been studied,
to the best of our knowledge. Neutrino is a particularly
interesting candidate for such a study. Neutrino oscillations are experimentally well established [2–7]. Such oscillations are possible if both of the following conditions
are satisfied:
• The neutrino flavour state is a linear superposition
of non-degenerate mass eigenstates.
• The time evolution of a flavour state is a coherent
superposition of the time evolution of the corresponding mass eigenstates.
The coherent time evolution implies that there is mode
entanglement between the mass eigenstates which make
up a flavour state. Since neutrinos interact only through
weak interactions, the effect of decoherence is minimal,
when compared to other particles such as electrons and
photons that are widely used in quantum information
processing.
The quest for understanding quantum correlations
could be thought to have begun with the efforts of
Einstein-Podolsky-Rosen (EPR) [8]. A better, quantitative understanding of EPR led to the development
of Bell’s inequality [9], with refinements leading to
the Bell-CHSH (Clauser-Horn-Shimony-Holt) inequalities [10]. Violation of Bell’s inequality quantifies the nonlocality inherent in the system. A weaker, though very
popular and widely studied measure of quantum correlations, is entanglement [11]. This has been applied to understand the process of teleportation [12]. A still weaker
measure is quantum discord [13, 14] and was developed
as the difference between the quantum generalizations of
two classically equivalent formulations of mutual information. Since states with are separable and hence have
no entanglement could still have non zero discord, our
present understanding of quantum correlations is that it
is a complex entity with many facets. There is now an
abundance of measures of quantum correlations such as
quantum work deficit [15], measurement induced disturbance [16] and dissonance [17].
In this paper we study several measures of quantum
correlations in the context of two-flavour νν ↔ ντ oscillations in long baseline accelerator neutrinos. Among
the measures studied are Bell’s inequality, concurrence,
discord and teleportation fidelity. We find that the study
of quantum correlations provides useful insights into the
nature of two flavour neutrino oscillations. We find that
these oscillations always violate Bell’s inequality and that
the teleportation fidelity is always greater than 2/3.
In this work, we first provide an introduction to the
quantum mechanics of two flavour neutrino oscillations.
Here we see that the mode entanglement comes in a natural setting. We then make a brief discussion of the various measures of quantum correlations used here, to study
neutrino oscillations. We then apply the correlation measures discussed, for νν ↔ ντ oscillations in accelerator
neutrinos. We finish with our conclusions.
II. QUANTUM MECHANICS OF TWO
FLAVOUR NEUTRINO OSCILLATIONS
∗
†
‡
akalok@iitj.ac.in
subhashish@iitj.ac.in
uma@phy.iitb.ac.in
It is well known that there are three flavour states of
neutrinos, νe , νµ and ντ [18, 19]. In the oscillation formalism, it is assumed that they mix via a 3×3 unitary matrix
Impact of initial granularity on the collective flow in
√
Pb-Pb collisions at sNN = 2.76 TeV
V P Konchakovski1 , W Cassing1 and V D Toneev2
1
arXiv:1411.5534v1 [nucl-th] 20 Nov 2014
2
Institute for Theoretical Physics, University of Giessen, 35392 Giessen, Germany
Joint Institute for Nuclear Research, 141980 Dubna, Russia
Abstract. The Parton-Hadron-String-Dynamics (PHSD) transport model is used
to study the influence of initial state granularity of the interacting system on flow
√
observables in Pb-Pb collisions at sN N = 2.76 TeV for different centralities. While
the flow coefficients v2 , v3 , v4 and v5 are reasonably described in comparison to the
data from the ALICE Collaboration for different centralities within the default setting,
no essential sensitivity is found with respect to the initial state granularity even for
very central collisions where the flow coefficients are dominated by the size of initial
state fluctuations. We attribute this lack of sensitivity to the low interaction rate of the
degrees-of-freedom in this very early phase of order ∼ 0.3 fm/c which is also in common
with the weakly interacting color glass condensate (CGC) or glasma approach.
PACS numbers: 25.75.-q, 24.85.+p, 12.38.Mh
Submitted to: J. Phys. G: Nucl. Phys.
arXiv:1411.5489v1 [astro-ph.CO] 20 Nov 2014
Prepared for submission to JCAP
Anisotropic inflation reexamined:
upper bound on broken rotational
invariance during inflation
Atsushi Naruko,a,b Eiichiro Komatsu,c,d Masahide Yamaguchia
a Department
of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo
152-8551, Japan
b APC (CNRS-Universit´
e Paris 7), 10 rue Alice Domon et L´eonie Duquet, 75205 Paris Cedex
13, France
c Max-Planck-Institut f¨
ur Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
d Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for
Advanced Study, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583,
Japan
E-mail: naruko@th.phys.titech.ac.jp
Abstract. The presence of a light vector field coupled to a scalar field during inflation makes
a distinct prediction: the observed correlation functions of the cosmic microwave background
(CMB) become statistically anisotropic. We study the implications of the current bound on
statistical anisotropy derived from the Planck 2013 CMB temperature data for such a model.
The previous calculations based on the attractor solution indicate that the magnitude of
anisotropy in the power spectrum is proportional to N 2 , where N is the number of e-folds
of inflation counted from the end of inflation. In this paper, we show that the attractor
solution is not compatible with the current bound, and derive new predictions using another
branch of anisotropic inflation. In addition, we improve upon the calculation of the mode
function of perturbations by including the leading-order slow-roll corrections. We find that
the anisotropy is roughly proportional to [2(εH + 4ηH )/3 − 4(c − 1)]−2 , where εH and ηH are
the usual slow-roll parameters and c is the parameter in the model, regardless of the form
of potential of an inflaton field. The bound from Planck implies that breaking of rotational
invariance during inflation (characterized by the background homogeneous shear divided by
the Hubble rate) is limited to be less than O(10−9 ). This bound is many orders of magnitude
smaller than the amplitude of breaking of time translation invariance, which is observed to
be O(10−2 ).
IFT-UAM/CSIC-14-122
arXiv:1411.5380v1 [hep-th] 19 Nov 2014
Higgs-otic Inflation and String Theory
Luis E. Ib´an
˜ez,a,b Fernando Marchesanob and Irene Valenzuelaa,b
a Departamento
de F´ısica Te´
orica UAM
b Instituto
de F´ısica Te´orica UAM/CSIC
Universidad Aut´onoma de Madrid
Cantoblanco, 28049 Madrid, Spain
Abstract
We propose that inflation is driven by a (complex) neutral Higgs of the MSSM extension of the SM, in a chaotic-like inflation setting. The SUSY breaking soft term
masses are of order 1012 − 1013 GeV, which is identified with the inflaton mass scale
and is just enough to stabilise the SM Higgs potential. The fine-tuned SM Higgs
has then a mass around 126 GeV, in agreement with LHC results. We point out
that the required large field excursions of chaotic inflation may be realised in string
theory with the (complex) inflaton/Higgs identified with a continuous Wilson line or
D-brane position. We show specific examples and study in detail a IIB orientifold
with D7-branes at singularities, with SM gauge group and MSSM Higgs sector. In
this case the inflaton/Higgs fields correspond to D7-brane positions along a two-torus
transverse to them. Masses and monodromy are induced by closed string G3 fluxes,
and the inflaton potential can be computed directly from the DBI+CS action. We
show how this action sums over Planck suppressed corrections, which amount to a
field dependent rescaling of the inflaton fields, leading to a linear potential in the large
field regime. We study the evolution of the two components of the Higgs/inflaton and
compute the slow-roll parameters for purely adiabatic perturbations. For large regions of initial conditions slow roll inflation occurs and 50-60 efolds are obtained with
r > 0.07, testable in forthcoming experiments. Our scheme is economical in the sense
that both EWSB and inflation originate in the same sector of the theory, all inflaton
couplings are known and reheating occurs efficiently.
Recoil corrections in antikaon-deuteron scattering
Maxim Maia , Vadim Barub,c , Evgeny Epelbaumb, Akaki Rusetskya
a Helmholtz–Institut
arXiv:1411.4881v1 [nucl-th] 18 Nov 2014
b Institut
f¨ur Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universit¨at Bonn, D-53115 Bonn, Germany
f¨ur theoretische Physik II, Fakult¨at f¨ur Physik und Astronomie, Ruhr-Universit¨at Bochum, 44780 Bochum, Germany
c Institute for Theoretical and Experimental Physics, 117218, B. Cheremushkinskaya 25, Moscow, Russia
Abstract
The recoil retardation effect in the K − d scattering length is studied. Using the non-relativistic effective field theory
approach, it is demonstrated that a systematic perturbative expansion of the recoil corrections in the parameter ξ =
MK /mN is possible in spite of the fact that K − d scattering at low energies is inherently non-perturbative due to the
¯ scattering lengths. The first order correction to the K − d scattering length due to single insertion
large values of the KN
of the retardation term in the multiple-scattering series is calculated. The recoil effect turns out to be reasonably small
even at the physical value of MK /mN ≃ 0.5.
Keywords: Antikaon-deuteron scattering; Multiple scattering series; Non-relativistic effective field theories;
Nucleon recoil;
PACS: 36.10.Gv, 13.75.Cs, 13.75.Jz
1. Introduction
Antikaon-nucleon scattering is an excellent testing ground for understanding the S U(3) QCD dynamics at low
energies in the one-baryon sector. Starting from the seminal paper [1], it is often described within the so-called
unitarized Chiral Perturbation Theory (ChPT), which uses the chiral potential calculated at a certain order (see, e.g.,
Refs. [2–10]). Different versions of the unitarized ChPT are available in literature. However, a common feature of
all formulations is a relatively large number of free parameters, which are fixed from the fit to the experimental data.
¯ scattering lengths, which “nail down” the amplitudes
An important part of the input is coming from the S-wave KN
¯ threshold and thus impose stringent constraints both on the scattering in the KN
¯ channel as well as the
at the KN
sub-threshold behavior of the amplitudes. The latter plays an important role in the study of the interaction of the K −
with nuclear medium (see, e.g., Ref. [11]).
The experiments with kaonic atoms have been carried out in order to extract the precise values of the S-wave
¯ scattering lengths – a goal that could be hardly achieved by using different experimental techniques. Recently,
KN
the energy shift and width of kaonic hydrogen were measured very accurately in the SIDDHARTA experiment at
DAΦNE [12] (for the earlier attempts, see, e.g., Refs. [13, 14]). These two quantities can be related to the K − p
scattering lengths via the so-called modified Deser-type formula, see Refs. [15, 16] (a general discussion of the
procedure of extracting the scattering lengths from the hadronic atom observables can be found, e.g., in a review
article [17]). The same experimental collaboration has made an attempt to measure the energy and the width of the
ground state of the kaonic deuterium as well. However, due to a small signal-to-background ratio, no clear signal
from the kaonic deuterium was detected [18]. Only an upper limit on the yield of the kaonic deuterium Kα line could
be determined which is important for the evaluation of the new experiments proposed at LNF [19] and J-PARC [20].
In addition, the kaonic 3 He and 4 He atoms have also been studied within the SIDDHARTA experiment.
¯ scatterWhat makes the experiments with kaonic deuterium extremely important is the fact that the S-wave KN
ing lengths are complex-valued, in difference, e.g., to the πN scattering lengths, which are real quantities. The πN
scattering lengths can be, in principle, determined directly on the basis of π− H data alone [21] while the level shift
of the pionic deuterium [22] is used as a complementary information to improve the accuracy in the extraction of
the πN scattering lengths, see Ref. [23] for the results of the latest combined analysis of pionic atoms. Meanwhile,
¯ system implies
extracting two complex scattering lengths a0 , a1 corresponding to the total isospin I = 0, 1 in the KN
Preprint submitted to Elsevier
November 19, 2014
MAN/HEP/2014/14
A Possible Two-component Flux for the High Energy Neutrino Events at IceCube
Chien-Yi Chen,1 P. S. Bhupal Dev,2 and Amarjit Soni1
1
Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA
2
Consortium for Fundamental Physics, School of Physics and Astronomy,
University of Manchester, Manchester M13 9PL, United Kingdom
arXiv:1411.5658v1 [hep-ph] 20 Nov 2014
(Dated: November 21, 2014)
Motivated by the indications of a possible deficit of muon tracks and also of an apparent energy gap between 300 TeV–1 PeV in the 3-year IceCube high-energy neutrino data, we question
the standard assumption of a single power-law flux with (1:2:0) neutrino flavor composition at an
astrophysical source. Instead, we entertain the possibility of another well-motivated source with
(1:0:0) composition and show that the resulting two-component flux provides a better fit to the
existing data. In particular, it naturally addresses the ‘muon deficit problem’ along with the energy
gap without invoking any New Physics interactions. Given the extreme importance of the flavor
composition for the correct interpretation of the underlying astrophysical processes as well as for
the ramification for particle physics, it is highly desirable that the flavor composition be extracted
from experiment as more data is accumulated.
I.
INTRODUCTION
The recent observation of ultra-high energy (UHE)
neutrino events at IceCube [1–3] in previously uncharted
energy regime has commenced a new era in Neutrino Astrophysics. With the 3-year data, the observed total of
37 candidate events reject a purely atmospheric explanation at 5.7σ [3] and strongly suggest an extra-terrestrial
origin. This provides a unique opportunity to directly
probe the energetic physical processes occurring in dense
astrophysical environments, which are otherwise inaccessible with traditional messengers like photons or charged
particles.
It is imperative for both astrophysics and particle
physics to understand all possible aspects of the UHE
neutrino events (see e.g. [4, 5]). Since no significant
clustering is observed [3] and there is no evidence for
point-like sources of astrophysical neutrinos [6], the current data suggests either many isotropically distributed
point sources or some spatially extended sources. Moreover, most of the UHE neutrino events have arrival directions in high galactic latitudes [3], thereby suggesting a dominant extragalactic component [7], which could
be attributed to various astrophysical sources. Typical examples are cosmic-ray (CR) reservoirs like starburst galaxies and galaxy clusters/groups [8], CR accelerators like active galactic nuclei (AGNs) [9], gamma-ray
bursts [10] and newborn pulsars [11], or even charmed
meson decay in mildly relativistic jets of supernovae [12].
A cosmogenic source due to UHECR interactions with
the CMB background is now disfavored [13]. However, a
sub-dominant galactic contribution, possibly associated
with known local large diffuse TeV to PeV γ-ray sources
at the galactic center [14] or the interstellar medium [15]
cannot be ruled out yet.
In the IceCube analyses so far, the astrophysical neutrinos are assumed to have originated from the decay
of charged pions/kaons produced through hadro-nuclear
(pp) or photo-hadronic (pγ) interactions of UHECRs in
a dense astrophysical system. The decay chain π ± →
µ± + νµ (¯
νµ ), µ± → e± + νe (¯
νe ) + ν¯µ (νµ ) leads to a flavor composition of (νe :νµ :ντ )S =(1:2:0)S at the source (S).
After the neutrino oscillations are averaged over an astronomical distance scale, the final composition on Earth
(E) becomes (1:1:1)E [16]. The flux of these neutrinos follows that of the progenitor protons, which is typically a
power-law spectrum Φ ∝ E −γ with γ ∼ 2 for a diffusive
Fermi-shock acceleration mechanism [17].
Using the (1:1:1)E flavor composition and assuming a
single-component E −γ flux over the entire energy range
of interest, it was shown [18, 19] that the 2-year IceCube data was largely consistent with the expectations
from the Standard Model (SM) neutrino-nucleon interactions within the known uncertainties. This provides a
unique test of the SM interactions involving the highest
energy neutrinos ever observed in Nature and any statistically significant deviations in the future data from
the SM expectations might call for a non-standard explanation. In fact, several New Physics scenarios have
been envisaged in this context, e.g. early-decay of a massive long-lived particle [20], decay [21] or annihilation [22]
of a heavy Dark Matter, secret neutrino interactions involving a light mediator [23], lepto-quark resonance [24],
decay of massive neutrinos to light ones over cosmological distances [25], mirror neutrinos [26], superluminal
neutrinos [27], color-octet neutrinos [28], TeV-scale gravity [29], and so on. Even within the SM framework, various other possibilities have been considered, e.g. the
Glashow resonance in ν¯e e− [30] and ν` γ scattering [31],
and interactions of nuclei with matter [32]. If the data
continues to be consistent with the SM predictions, one
can put useful constraints on some of the exotic scenarios
mentioned above which are otherwise difficult to probe
in low-energy laboratory experiments [5].
Type II Seesaw Higgsology and LEP/LHC constraints
Abdesslam Arhrib,1 Rachid Benbrik,2 Gilbert Moultaka∗ ,3 and Larbi Rahili4
1
D´epartement de Math´ematiques, Facult´e des Sciences et Techniques, Tanger, Morocco
arXiv:1411.5645v1 [hep-ph] 20 Nov 2014
2
Facult´e Polydisciplinaire, Universit´e Cadi Ayyad, Sidi Bouzid, Safi-Morocco
3
Laboratoire Charles Coulomb (L2C) UMR 5221
CNRS-Univ. Montpellier 2, Montpellier, F-France
4
Laboratoire de Physique des Hautes Energies et Astrophysique,
Universit´e Cadi-Ayyad, FSSM, Marrakech, Morocco
(Dated: November 21, 2014)
∗
corresponding author
1
IPPP/14/99, DCPT/14/198
An upper limit on the scale of new physics phenomena
arXiv:1411.5633v1 [hep-ph] 20 Nov 2014
from
rising cross sections in high multiplicity Higgs and vector boson events
Joerg Jaeckel1 and Valentin V. Khoze2
1
2
Institut f¨
ur theoretische Physik, Universit¨
at Heidelberg,
Philosophenweg 16, 69120 Heidelberg, Germany
Institute for Particle Physics Phenomenology, Department of Physics,
South Road, Durham DH1 3LE, United Kingdom
Abstract
In very high energy scattering events production of multiple Higgs and electroweak gauge
bosons becomes possible. Indeed the perturbative cross section for these processes grows
with increasing energy, eventually violating perturbative unitarity. In addition to perturbative unitarity we also examine constraints on high multiplicity processes arising from
experimentally measured quantities. These include the shape of the Z-peak and upper limits on scattering cross sections of cosmic rays. We find that the rate of high multiplicity
electroweak processes will exceed these upper limits at energies not significantly above what
can be currently tested experimentally. This leaves two options: 1) The electroweak sector
becomes truly non-perturbative in this regime or 2) Additional physics beyond the Standard
Model is needed. In both cases novel physics phenomena must set in before these energies
are reached. Based on the measured Higgs mass we estimate the critical energy to be in
the range of 103 TeV but we also point out that it can potentially be significantly less than
that.
1
UWTHPH 2014-32
November 21, 2014
Charm and Bottom Masses from Sum Rules
with a Convergence Test
arXiv:1411.5597v1 [hep-ph] 20 Nov 2014
Bahman Dehnadi ∗,1 , Andr´
e H. Hoang ∗,† , Vicent Mateu ∗
∗
University of Vienna, Faculty of Physics, Boltzmanngasse 5, A-1090 Wien, Austria
†
Erwin Schr¨
odinger International Institute for Mathematical Physics, University of
Vienna, Boltzmanngasse 9, A-1090 Vienna, Austria
In this talk we discuss results of a new extraction of the MS charm
quark mass using relativistic QCD sum rules at O(αs3 ) based on moments
of the vector and the pseudoscalar current correlators and using the available experimental measurements from e+ e− collisions and lattice results,
respectively. The analysis of the perturbative uncertainties is based on
different implementations of the perturbative series and on independent
variations of the renormalization scales for the mass and the strong coupling following a work we carried out earlier. Accounting for the perturbative series that result from this double scale variation is crucial since some
of the series can exhibit extraordinarily small scale dependence, if the two
scales are set equal. The new aspect of the work reported here adresses
the problem that double scale variation might also lead to an overestimate
of the perturbative uncertainties. We supplement the analysis by a convergence test that allows to quantify the overall convergence of QCD perturbation theory for each moment and to discard series that are artificially
spoiled by specific choices of the renormalization scales. We also apply the
new method to an extraction of the MS bottom quark mass using experimental moments that account for a modeling uncertainty associated to
the continuum region where no experimental data is available. We obtain
mc (mc ) = 1.287 ± 0.020 GeV and mb (mb ) = 4.167 ± 0.023 GeV.
PRESENTED AT
International Workshop on the CKM Unitarity Triangle
Vienna, Austria, September 8–12, 2014
1
Presenter
Introduction: Precise and reliable determinations of the charm and bottom quark
masses are an important input for a number of theoretical predictions such as Higgs
branching ratios to charm and bottom quarks or for the corresponding Yukawa couplings [1]. They also affect the theoretical predictions of radiative and inclusive B
decays, as well as rare kaon decays. For example, the inclusive semileptonic decay
rate of B mesons depends on the fifth power of the bottom quark mass. These weak
decays provide crucial methods to determine elements of the CKM matrix and which
in turn are important for testing the validity of the Standard Model and for indirect
searches of new physics. In this context having a reliable estimate of uncertainties of
the quark masses is as important as knowing their values precisely [2]. Due to confinement quark masses are not physical observables. Rather, they are scheme-dependent
parameters of the QCD Lagrangian which have to be determined from quantities that
strongly depend on them.
One of the most precise tools to determine the charm and bottom quark masses is
the QCD sum rule method where weighted averages of the normalized cross section
Re+ e− → qq +X , with q = c, b, can be related to moments of the quark vector current
correlator ΠV which can be calculated in perturbation theory using the OPE:
Z
ds
σe+ e− → cc +X (s)
Re+ e− → cc +X (s) =
Mn =
Re+ e− → qq +X (s) ,
,
(1)
sn+1
σe+ e− → µ+ µ− (s)
2 2 12π Qq d n
2 µ
th
µ
, j (x) = ψ(x)γ ψ(x) ,
Mn =
ΠV (q )
n!
dq 2
q 2 =0
Z
2
2
iqx
gµν q − qµ qν ΠV (q ) = − i dx e h 0 |T jµ (x)jν (0)| 0 i .
p
√
Here Qq is the quark electric charge and s = q 2 is the e+ e− center of mass energy.
Since the integration over the experimental R-ratio stretches from the quark pair
threshold up to infinity and since useful experimental measurements only exist for
energies up to around 11 GeV, the method relies on using theory input for energies
above that scale (which we call “continuum”). For the charm case the combination of
all available measurements is sufficient to render the experimental moments independent of uncertainties one assigns to the theory input for the continuum region [3]. For
the bottom case the dependence on the continuum theory input is very large, and the
dependence of the low-n experimental moments on unavoidable assumptions about
the continuum error can be the most important component of the error budget. In
fact, the use of the first moment M1 appears to be excluded until experimental data
become available for higher energies.
Alternatively one can also consider moments of the pseudoscalar current correlator. Experimental information on the correlator ΠP is not available in a form useful
for quark mass determinations, but for charm quarks very precise lattice calculations
have become available recently [8]. For the pseudo-scalar correlator it turns out that
1
Quarkonia Disintegration due to time dependence of the q q¯ potential in Relativistic
Heavy Ion Collisions
Partha Bagchi∗ and Ajit M. Srivastava†
Institute of Physics, Bhubaneswar, Odisha, India 751005
arXiv:1411.5596v1 [hep-ph] 20 Nov 2014
Rapid thermalization in ultra-relativistic heavy-ion collisions leads to fast changing potential
between a heavy quark and antiquark from zero temperature potential to the finite temperature
one. Time dependent perturbation theory can then be used to calculate the survival probability
of the initial quarkonium state. In view of very short time scales of thermalization at RHIC and
LHC energies, we calculate the survival probability of J/ψ and Υ using sudden approximation. Our
results show that quarkonium decay may be significant even when temperature of QGP remains low
enough so that the conventional quarkonium melting due to Debye screening is ineffective.
PACS numbers: PACS numbers: 25.75.-q, 11.27.+d, 14.40.Lb, 12.38.Mh
Suppression of heavy quarkonia as a signal for the
quark-gluon plasma phase in relativistic heavy-ion collisions has been investigated intensively since the original
proposal by Matsui and Satz [1]. The underlying physical
picture of this suppression is that due to deconfinment,
potential between q q¯ gets Debye screened, resulting in
the swelling of quarkonia. If the Debye screening length
of the medium is less than the radius of quarkonia, then
q q¯ may not form bound states, leading to melting of the
initial quarkonium. Due to this melting, the yield of
quarkonia will be suppressed. This was proposed as a
signature of QGP and has been observed experimentally
[2]. However, there are other factors too that can lead
to the suppression of J/ψ because of which it has not
been possible to use J/ψ suppression as a clean signal
for QGP.
In the above picture, suppression of quarkonia occurs
when the temperature of QGP achieves a certain value,
TD , so that the Debye screening melts the quarkonium
bound state. Thus, if the temperature remains smaller
than TD , so that Debye screening length remains larger
than the quarkonia size, no suppression is expected. This
type of picture is consistent with the adiabatic evolution
of a quantum state under changing potential. Original
quarkonia has a wave function appropriate for zero temperature potential between a q and q¯. If the environment
of the quarkonium changes to a finite temperature QGP
adiabatically, with Debye screened potential, the final
state will evolve to the quarkonium state corresponding to the finite temperature potential. If temperature
remains below TD , quarkonium wave function changes
(adiabatically) but it survives as the quarkonium.
We question this assumption of adiabatic evolution for
ultra-relativistic heavy-ion collisions, such as at RHIC,
and especially at LHC. At such energies, it is possible that thermalization is achieved in a very short time,
about 0.25 fm for RHIC and even smaller about 0.1 fm for
∗ Electronic
† Electronic
address: partha@iopb.res.in
address: ajit@iopb.res.in
LHC [3]. Even conservatively, thermalization is achieved
within 1 fm as suggested by the elliptic flow measurements [4]. For J/ψ and even for Υ, typical time scale of
q q¯ dynamics will be at least 1-2 fm from the size of the
bound state and the fact that q q¯ have non-relativistic velocities. Also, ∆E between J/ψ and its next excited state
(χ) is about 300 MeV (400 MeV for Υ states), leading to
transition time scale ∼ 0.7 fm (0.5 fm for Υ). Thus the
change in the potential between q and q¯ occurs in a time
scale which is at most of the same order, and likely much
shorter than, the typical time scale of the dynamics of the
q q¯ system, or the time scale of transition between relevant states. The problem, therefore, should be treated
in terms of a time dependent perturbation and survival
probability of quarkonia should be calculated under this
perturbation. It is immediately clear that even if the final
temperature remains less than TD , if the change in potential is fast enough invalidating the adiabatic assumption, then transition of initial quarkonium state to other
excited states will occur. Such excited states will have
much larger size, typically larger than the Debye screening length, and will melt away. Thus quarkonia melting
can occur even when QGP temperature remains below
TD . We mention that adiabatic evolution of quarkonia
states has been discussed earlier for the cooling stage of
QGP in relativistic heavy ion collisions in the context of
sequential suppression of quarkonia states [5]. However,
as far as we are aware, validity of adiabatic evolution
during the thermalization stage has not been discussed
earlier.
Given the large difference between thermalization time
scale of order 0.1 - 0.2 fm [3], and the time scale of q q¯
dynamics in a quarkonium bound state being of order 1-2
fm (or the time scale of transition between relevant states
being 0.5 - 0.7 fm), it may be reasonable to use the sudden
perturbation approximation. The initial wave function of
the quarkonium cannot change under this sudden perturbation. Thus, as soon as thermalization is achieved with
QGP temperature being T0 (which may remain less than
TD for the quarkonium state under consideration), the
initial quarkonium wave function is no longer an energy
eigen state of the new Hamiltonian with the q q¯ potential
Could the near–threshold XY Z states be simply kinematic effects?
Feng-Kun Guo1∗ , Christoph Hanhart2† , Qian Wang2‡ , Qiang Zhao3§
arXiv:1411.5584v1 [hep-ph] 20 Nov 2014
3
1
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik and Bethe Center
for Theoretical Physics, Universit¨
at Bonn, D-53115 Bonn, Germany
2
Institut f¨
ur Kernphysik and Institute for Advanced Simulation,
Forschungszentrum J¨
ulich, D–52425 J¨
ulich, Germany
Institute of High Energy Physics and Theoretical Physics Center for Science Facilities,
Chinese Academy of Sciences, Beijing 100049, China
(Dated: November 21, 2014)
We demonstrate that the spectacular structures discovered recently in various experiments and
named as X, Y and Z states cannot be purely kinematic effects. Their existence necessarily calls
for nearby poles in the S–matrix and they therefore qualify as states.
PACS numbers: 14.40.Rt, 13.75.Lb, 13.20.Gd
In recent years various narrow (widths from well below 100 MeV down to values even below 1 MeV) peaks
were discovered both in the charmonium as well as in
the bottomonium mass range that do not fit into the
so far very successful quark model. For instance, the
most prominent ones include X(3872) [1], Zc (3900) [2–
4], Zc (4020) [5–8], Zb (10610) and Zb (10650) [9], which
¯ ∗ , DD
¯ ∗ , D∗ D
¯ ∗, BB
¯ ∗ and B ∗ B
¯∗
are located close to DD
thresholds in relative S–waves, respectively. Apart from
other interpretations, such as hadro-quarkonia [10, 11],
hybrids [12–14], and tetraquarks [15, 16] (for recent reviews we refer to Refs. [17, 18]), due to their proximity to
the thresholds these five states were proposed to be of a
molecular nature [19–37]. As an alternative explanation
various groups conclude from the mentioned proximity of
the states to the thresholds that the structures are simply kinematical effects [38–45] that necessarily occur near
every S-wave threshold. Especially, it has been claimed
that the structures are not related to a pole in the S–
matrix and therefore should not be interpreted as states.
In this letter we show that the latter statement is based
on calculations performed within an inconsistent formalism. In particular, we demonstrate that, while there is
always a cusp at the opening of an S–wave threshold,
in order to produce peaks as pronounced and narrow
as observed in experiment non-perturbative interactions
amongst the heavy mesons are necessary, and as a consequence, there is to be a near-by pole. Or, formulated
the other way around: if one assumes the two–particle
interactions to be perturbative, as it is implicitly done in
Refs. [38–45], the cusp should not appear as a prominent
narrow peak. This statement is probably best illustrated
by the famous K ± → π ± π 0 π 0 data [46]: the cusp that
appears in the π 0 π 0 invariant mass distribution at the
∗ Email
address:
address:
‡ Email address:
§ Email address:
† Email
fkguo@hiskp.uni-bonn.de
c.hanhart@fz-juelich.de
q.wang@fz-juelich.de
zhaoq@ihep.ac.cn
π
Y
D
D*
π
Y
D
D
D*
D*
(a)
π
Y
(b)
D
D
D
D*
D*
D*
(c)
FIG. 1: The tree-level, one-loop and two-loop Feynman dia¯ ∗.
grams for Y (4260) → πDD
π + π − threshold is a very moderate kink, since the ππ
interactions are sufficiently weak to allow for a perturbative treatment (for a comprehensive theoretical framework and related references we refer to Ref. [47]).
To be concrete, in this paper we demonstrate our argument on the example of an analysis of the existing data on
the Zc (3900), but it should be clear that the reasoning as
such is general and applies to all structures observed very
near S–wave thresholds such as those above-mentioned
XY Z states. To illustrate our point, we here do not aim
for field theoretical rigor but use a very simple separable
interaction for all vertices accompanied by loops regularized with a Gaussian regulator. This regulator will at the
same time control the drop-off of the amplitudes as will
be discussed below. Accordingly, we write for the Lagrangian that produces the tree–level vertices (here and
¯ ∗ for the proper
in what follows we generically write DD
arXiv:1411.5575v1 [hep-ph] 20 Nov 2014
ACFI-T14-21
Electroweak Baryogenesis in the Exceptional Supersymmetric
Standard Model
Wei Chao ∗
Amherst Center for Fundamental Interactions, Department of Physics,
University of Massachusetts-Amherst Amherst, MA 01003
Abstract
We study electroweak baryogenesis in the E6 inspired exceptional supersymmetric standard
model (E6 SSM). The relaxation coefficients driven by singlinos and the new gaugino as well as
the transport equation of the Higgs supermultiplet number density in the E6 SSM are calculated.
Our numerical simulation shows that both CP-violating source terms from singlinos and the new
gaugino can solely give rise to a correct baryon asymmetry of the Universe via the electroweak
baryogenesis mechanism.
∗
Electronic address: chao@physics.umass.edu
1
New Higgs Inflation in a No-Scale Supersymmetric SU(5) GUT
John Ellis a , Hong-Jian He b , Zhong-Zhi Xianyu b
a
arXiv:1411.5537v1 [hep-ph] 20 Nov 2014
Theoretical Particle Physics and Cosmology Group,
Department of Physics, King’s College London, London WC2R 2LS, UK;
Theory Division, CERN, CH-1211 Geneva 23, Switzerland.
b
Institute of Modern Physics and Center for High Energy Physics, Tsinghua University, Beijing 100084, China;
Center for High Energy Physics, Peking University, Beijing 100871, China.
Higgs inflation is attractive because it identifies the inflaton with the electroweak Higgs boson.
In this work, we construct a new class of supersymmetric Higgs inflationary models in the no-scale
supergravity with an SU(5) GUT group. Extending the no-scale K¨
ahler potential and SU(5) GUT
superpotential, we derive a generic potential for Higgs inflation that includes the quadratic monomial
potential and a Starobinsky-type potential as special limits. This type of models can accommodate
a wide range of the tensor-to-scalar ratio r = O(10−3 − 10−1 ) , as well as a scalar spectral index
ns ∼ 0.96 .
PACS numbers: 98.80.Cq, 04.65.+e, 12.10.-g, 12.60.Jv
KCL-PH-TH/2014-48, LCTS/2014-49, CERN-PH-TH/2014-230
1. Introduction
Cosmological inflation [1] resolves conceptual dilemma
of the standard big-bang cosmology such as the horizon and flatness problems, and predicts that large-scale
structures in the Universe originated from a nearly scaleinvariant spectrum of density perturbations, which is well
consistent with cosmological observations [2, 3]. Theories of cosmological inflation postulate a scalar field, the
inflaton, whose field energy drove an early epoch of nearexponential expansion. Before the LHC Higgs discovery,
it was very tempting to identify this inflaton as the Higgs
boson of the Standard Model (SM) [4], a very economical and predictive scenario. However, the recent LHC
and Tevatron measurements of the Higgs and top quark
masses indicate that the SM Higgs potential turns negative at ∼ 1011 GeV [5], which is lower than the typical
cosmic inflation scale ∼ 1016 GeV. This means that new
physics is indispensable for our universe to reach a stable
electroweak vacuum after inflation.
On the other hand, the SM suffers from the naturalness problem of stabilizing the electroweak scale against
radiative corrections to Higgs mass, for which one possible solution is low-energy supersymmetry (SUSY). Remarkably, it was shown [6] that the instability of the SM
Higgs potential can be cured without severe fine-tuning
by adding bosonic and fermionic degrees of freedom, ending up with a theory much like SUSY. In the simplest example along this line, it was also shown [7] that adding
a new boson-fermion pair does lead to successful Higgs
inflation with a wider range of the tensor-to-scalar ratio
than that of the conventional Higgs inflation.
Combining Higgs inflation with SUSY is a challenging
task. For instance, it was found in [8] that building Higgs
inflation in the MSSM with a minimal K¨
ahler potential
is not viable. On the other hand, in the NMSSM one encounters a tachyonic instability along the direction of the
additional singlet scalar [9], though this can be cured by
adding higher-order terms to the K¨
ahler potential [10].
Models of this kind were built in the minimal SU(5) GUT
with a (strongly) modified no-scale K¨ahler potential and
invoking a large nonminimal Higgs-curvature coupling,
which gave a small tensor-to-scalar ratio r [11]. Another
type of GUT inflation model is F -term hybrid inflation,
which generally leads to very small r as well [12], though
an enhanced value of r could be achieved with a particular choice of K¨ahler potential [13]. Finally, it was
shown in [14] that no-scale supergravity naturally accommodates models of inflation that yield predictions similar
to the Starobinsky model [15] and the original model of
Higgs inflation [4], as well as allowing more general inflationary potentials that could yield larger values of r [16].
In this work, we construct a new class of Higgs inflation models, using the framework of no-scale supergravity (SUGRA) [17] and embedded in the supersymmetric SU(5) grand unified theory (GUT). There are many
motivations for this construction, of which we mention
three. Firstly, the inflation scale may well be close to
the GUT scale, according to CMB measurements [2, 3],
so it is very attractive to embed Higgs inflation into a
GUT. Secondly, no-scale SUGRA emerges from simple
compactifications of string theory [18]. Thirdly, the flat
directions in no-scale SUGRA are advantageous for cosmological applications [19].
For our new type of supersymmetric Higgs inflation in
the no-scale SU(5) GUT framework, we adopt the minimal field content, with simple extensions of the no-scale
K¨ahler potential and minimal SU(5) GUT superpotential. We derive a generic inflationary potential that interpolates between a quadratic monomial potential and
a Starobinsky-type potential. The corresponding predictions of the tensor-to-scalar ratio r and spectral index
ns can accommodate the Planck and BICEP2 observations [2, 3]. A notable feature of this no-scale SUSY
GUT Higgs inflation scenario is that it does not invoke
any non-minimal coupling between the Higgs fields and
the Ricci curvature, i.e., all Higgs bosons couple mini-
Decrypting SO(10)-inspired leptogenesis
arXiv:1411.5478v1 [hep-ph] 20 Nov 2014
Pasquale Di Bari1, Luca Marzola2, Michele Re Fiorentin1
1
Physics and Astronomy, University of Southampton,
Southampton, SO17 1BJ, U.K.
2
Institute of Physics, University of Tartu,
Ravila 14c, 50411 Tartu, Estonia.
November 21, 2014
Abstract
Encouraged by the recent results from neutrino oscillation experiments, we perform an analytical study of SO(10)-inspired models and leptogenesis with hierarchical right-handed (RH) neutrino spectrum. Under the approximation of negligible
misalignment between the neutrino Yukawa basis and the charged lepton basis, we
find an analytical expression for the final asymmetry directly in terms of the low
energy neutrino parameters that fully reproduces previous numerical results. This
expression also shows that is possible to identify an effective leptogenesis phase for
these models. When we also impose the wash-out of a large pre-existing asymp,i
, the strong thermal (ST) condition, we derive analytically all those
metry NB−L
constraints on the low energy neutrino parameters that characterise the ST-SO(10)inspired leptogenesis solution, confirming previous numerical results. In particular
we show why, though neutrino masses have to be necessarily normally ordered, the
solution implies an analytical lower bound on the effective neutrino-less double beta
p,i
decay neutrino mass, mee & 8 meV, for NB−L
= 10−3 , testable with next generation experiments. This, in combination with an upper bound on the atmospheric
mixing angle, necessarily in the first octant, forces the lightest neutrino mass within
P
a narrow range m1 ' (10–30) meV (corresponding to i mi ' (75–125) meV). We
also show why the solution could correctly predict a non-vanishing reactor neutrino
mixing angle and requires the Dirac phase to be in the fourth quadrant, implying
sin δ (and JCP ) negative as now hinted by current global analyses. Many of the
analytical results presented (expressions for the orthogonal matrix, RH neutrino
mixing matrix, masses and phases) can have applications beyond leptogenesis.
Higher-twist contributions to the transverse momentum broadening in semi-inclusive
deep inelastic scattering off large nuclei
Jia Jun Zhang,1, 2 Jian-Hua Gao,3, 2 and Xin-Nian Wang1, 2, 4
1
arXiv:1411.5435v1 [hep-ph] 20 Nov 2014
Institute of Particle Physics, Central China Normal University, Wuhan 430079, China
2
Key Laboratory of Quark and Lepton Physics (MOE),
Central China Normal University, Wuhan 430079, China
3
Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment,
Institute of Space Sciences, Shandong University, Weihai 264209, China
4
Nuclear Science Division, MS 70R0319, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
Multiple scattering leads to transverse momentum broadening of the struck quark in semi-inclusive
deeply inelastic scatterings (SIDIS). Nuclear broadening of the transverse momentum squared at
the leading twist is determined by the twist-four collinear quark-gluon correlation function of the
target nucleus that is in turn related to the jet transport parameter inside the nuclear medium. The
twist-six contributions to the transverse momentum broadening are calculated as power corrections
∼ 1/Q2 . Such power corrections are found to have no extra nuclear enhancement beyond the twistfour matrix elements and are determined by the nuclear modification of collinear parton distribution
and correlation functions. They become important for an accurate extraction of the jet transport
parameter inside large nuclei and its scale evolution at intermediate values of the hard scale Q2 .
PACS numbers: 25.75.-q, 13.88.+e, 12.38.Mh, 25.75.Nq
I.
INTRODUCTION
Multiple scattering of a propagating parton inside a
medium leads to many interesting phenomena such as
transverse momentum broadening and parton energy loss
[1–6]. These phenomena as observed in experiments in
both high-energy heavy-ion collisions and semi-inclusive
deeply inelastic scatterings (SIDIS) can in turn be used to
extract properties of hot and cold nuclear matter. One of
these medium properties as probed by propagating partons is the jet transport parameter qˆ. It is defined as
the transverse momentum broadening squared per unit
length [2] and measures the interaction strength between
the energetic parton and the medium. A recent comprehensive phenomenological study [7] of experimental
data on jet quenching in high-energy heavy-ion collisions
at both the Relativistic Heavy-ion Collider (RHIC) and
the Large Hadron Collider (LHC) has extracted values of
the jet transport parameter at the center of the produced
dense matter. They are about two orders of magnitude
higher than that in a cold nucleus as extracted from experimental data on semi-inclusive deeply inelastic scatterings (SIDIS) [8, 9]. Further improvements in the accuracy of the determination of the jet transport parameter
depend on the study of parton energy loss and the transverse momentum broadening at the next-to-leading order
[10] and evolution of the jet transport parameter [11–14].
Within the framework of generalized collinear factorization, multiple parton scattering and transverse momentum broadening can be expressed in terms of nuclear enhanced higher-twist contributions which depend
on the twist-4 parton correlation functions [15–18]. In
the same framework, we can also calculate parton energy loss and the leading hadron suppression [6, 19] in
SIDIS. In this paper we make the first attempt to calculate the first power corrections to the transverse momen-
tum broadening in SIDIS off a large nucleus. Similar to
leading higher-twist corrections to hadron spectra, such
power corrections to the transverse momentum broadening can become non-negligible for intermediate values of
the hard scale Q2 . Inclusion of these higher-twist corrections should be important for a more accurate determination of the jet transport parameter from experimental
data on transverse momentum broadening and its scale
evolution.
Multiple soft interactions between the struck quark
and the remnant nucleus in SIDIS can also be resummed
in the eikonal limit into the gauge link in the transverse
momentum dependent (TMD) parton distribution functions [20]. The transverse momentum broadening in a
large nucleus arises naturally from the expectation value
of the gauge link between the nuclear state. Under a maximal two-gluon correlation approximation, the transverse
momentum broadening takes the form of a Gaussian distribution with the width given by the path-integrated jet
transport parameter [21]. Within a systematic collinear
expansion of the hard parts of partonic scattering, one
can express the cross section of SIDIS in terms of TMD
parton distribution and correlation functions with different power corrections [22]. Calculations of the SIDIS
cross section have been carried out in the leading order
and up to twist-4 power corrections [23]. The results have
been applied to the study of nuclear dependence of the
azimuth asymmetry in both unpolarized [24] and polarized nuclear targets [25, 26]. We will employ these cross
sections in this paper to study the transverse momentum
broadening up to O(1/Q2 ) corrections.
The remainder of this paper is organized as the following. In Section II, we present the kinematics of
SIDIS and review the differential cross section of the
SIDIS process in terms of the TMD parton distribution
and correlation functions within the collinear expansion.
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–??
Effective Lagrangian approach to the EWSB sector
J. Gonzalez–Fraile
arXiv:1411.5364v1 [hep-ph] 19 Nov 2014
Departament d’Estructura i Constituents de la Mat`eria and ICC-UB, Universitat de Barcelona.
Institut f¨ur Theoretische Physik, Universit¨at Heidelberg.
Abstract
In a model independent framework, the effects of new physics at the electroweak scale can be parametrized in
terms of an effective Lagrangian expansion. Assuming the S U(2)L xU(1)Y gauge symmetry is linearly realized, the
expansion at the lowest order span dimension–six operators built from the observed Standard model (SM) particles,
in addition to a light scalar doublet. After a proper choice of the operator basis we present a global fit to all the
updated available data related to the electroweak symmetry breaking sector: triple gauge boson vertex (TGV) collider
measurements, electroweak precision tests and Higgs searches. In this framework modifications of the interactions of
the Higgs field to the electroweak gauge bosons are related to anomalous TGV’s, and given the current experimental
precision, we show that the analysis of the latest Higgs boson data at the LHC and Tevatron gives rise to strong
bounds on TGV’s that are complementary to those from direct TGV measurements. Interestingly, we present how
this correlated pattern of deviations from the SM predictions could be different for theories based on a non–linear
realization of the S U(2)L xU(1)Y symmetry, characteristic of for instance composite Higgs models. Furthermore,
anomalous TGV signals expected at first order in the non–linear realization may appear only at higher orders of the
linear one, and viceversa. Their study could lead to hints on the nature of the observed boson.
Keywords: Higgs, effective Lagrangian, gauge couplings, LHC
1. Introduction
After the discovery of the Higgs boson [1], we can finally analyze a particle that seems directly related to the
electroweak symmetry breaking (EWSB) mechanism.
Thus, almost fifty years since the Standard model (SM)
Higgs boson was postulated [2], the study of the discovered particle properties can be used for the first time
as a way to access the mechanism responsible for the
EWSB. In particular, in the present note we focus on
the analysis of the Higgs interactions to the rest of SM
particles. A huge variety of data has already been collected, not only from Higgs searches at both Tevatron
and the LHC, but also from the measurements of triple
gauge boson vertices (TGV)’s at the colliders and from
Email address: fraile@thphys.uni-heidelberg.de
(J. Gonzalez–Fraile)
the low energy electroweak precision measurements. In
this context we present a framework suitable to study
the nature of the observed state via the analysis of its
couplings, exploiting all the existing data sets. Pursuing a model independent analysis of the Higgs interactions, the effective Lagrangian approach [3–5] is
arguably one of the most motivated frameworks from
the theoretical point of view, given the lack of observation of any other new resonance. Hence, the effective Lagrangian is useful as a model independent way to
parametrize the low energy deviations in the Higgs interactions caused by New Physics (NP). Following this
motivation we present on the first part of this note the
effective Lagrangian expansion based on the assumption that the observed state is introduced as a doublet of
S U(2)L , where then the S U(2)L ⊗ U(1)Y symmetry is
linearly realized in the effective theory which describes
the indirect NP effects at LHC energies [6]. After pre-
Inflationary dynamics of
kinetically-coupled gauge fields
arXiv:1411.5362v1 [hep-ph] 19 Nov 2014
Ricardo Z. Ferreira∗ and Jonathan Ganc†
CP3 -Origins, Center for Cosmology and Particle Physics Phenomenology
University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Abstract
We investigate the inflationary dynamics of two kinetically-coupled massless
U (1) gauge fields with time-varying kinetic-term coefficients. Ensuring that the
system does not have strongly coupled regimes shrinks the parameter space. Also,
we further restrict ourselves to systems that can be quantized using the standard
creation, annihilation operator algebra. This second constraint limits us to scenarios where the system can be diagonalized into the sum of two decoupled, massless,
vector fields with a varying kinetic-term coefficient.
Such a system might be interesting for magnetogenesis because of how the strong
coupling problem generalizes. We explore this idea by assuming that one of the
gauge fields is the Standard Model U (1) field and that the other dark gauge field
has no particles charged under its gauge group. We consider whether it would be
possible to transfer a magnetic field from the dark sector, generated perhaps before
the coupling was turned on, to the visible sector. We also investigate whether the
simple existence of the mixing provides more opportunities to generate magnetic
fields. We find that neither possibility works efficiently, consistent with the wellknown difficulties in inflationary magnetogenesis.
Contents
1 Introduction
2
2 Kinetic Mixing of Gauge Fields
2.1 Decoupling the kinetic mixing . . . . . . . . . . . . . . . . . . . . . . . . .
4
5
3 Quantum considerations
3.1 Avoiding strongly coupled regimes . . . . . . . . . . . . . . . . . . . . . . .
3.2 Quantization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
6
7
4 Solvable Scenarios
8
∗
†
ferreira@cp3.dias.sdu.dk
ganc@cp3.dias.sdu.dk
1