Mon·Apr 18, 2016Monday·April 18, 2016

1. 01*

   Probing Transverse Momentum Broadening in Heavy Ion Collisions

   A.H. Mueller🇺🇸 · Bin Wu🇫🇷 · Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸

   We study the dijet azimuthal de-correlation in relativistic heavy ion collisions as an important probe of the transverse momentum broadening effects of a high energy jet traversing the quark-gluon plasma. We take into account both the soft gluon radiation in vacuum associated with the Sudakov logarithms and the jet P_T-broadening effects in the QCD medium. We find that the Sudakov effects are dominant at the LHC, while the medium effects can play an important role at RHIC energies. This explains why the LHC experiments have not yet observed sizable P_T-broadening effects in the measurement of dijet azimuthal correlations in heavy ion collisions. Future investigations at RHIC will provide a unique opportunity to study the P_T-broadening effects and help to pin down the underlying mechanism for jet energy loss in a hot and dense medium.

   hep-phnucl-exnucl-thPLB(2016)·75 citations
2. 02*

   Asymmetric Dark Matter in the Shear--dominated Universe

   Hoernisa Iminniyaz🇨🇳

   We explore the relic abundance of asymmetric Dark Matter in shear--dominated universe in which it is assumed the universe is expanded anisotropically. The modified expansion rate leaves its imprint on the relic density of asymmetric Dark Matter particles if the asymmetric Dark Matter particles are decoupled in shear dominated era. We found the relic abundances for particle and anti--particle are increased. The particle and anti--particle abundances are almost in the same amount for the larger value of the shear factor $x_e$ which makes the indirect detection possible for asymmetric Dark Matter. We use the present day Dark Matter density from the observation to find the constraints on the parameter space in this model.

   hep-phPLB(2017)·6 citations
3. 03*

   LHC Signatures Of Scalar Dark Energy

   Philippe Brax🇫🇷 · Clare Burrage🇬🇧 · Christoph Englert🇬🇧 · Michael Spannowsky🇬🇧

   Scalar dark energy fields that couple to the Standard Model can give rise to observable signatures at the LHC. In this work we show that $t\bar{t}+$missing energy and mono-jet searches are suitable probes in the limit where the dark energy scalar is stable on collider distances. We discuss the prospects of distinguishing the dark energy character of new physics signals from dark matter signatures and the possibility of probing the self-interactions of the dark energy sector.

   hep-phastro-ph.COPRD(2016)·42 citations
4. 04*

   Cumulative production of pions by heavy baryonic resonances in proton-nucleus collisions

   A. Motornenko🇺🇦 · M. I. Gorenstein🇺🇦

   Pion production in proton-nucleus (p+A) collisions outside the kinematical boundary of proton-nucleon (p+N) reactions, the so-called cumulative effect, is studied. Restrictions from energy-momentum conservation on the energy of pions emitted in the backward direction in the target rest frame are analyzed. It is assumed that the cumulative pions are produced in p+A reactions by heavy baryonic resonances. The baryonic resonances are first created in p+N reactions. Due to successive collisions with nuclear nucleons the masses of these resonances may then increase and, simultaneously, their longitudinal velocities decrease. We also use the Ultra relativistic Quantum Molecular Dynamics model to reveal the key role of successive collisions of baryonic resonances with nuclear nucleons for cumulative pion production in p+A reactions. Further experimental studies of cumulative hadron production in p+A reactions at high collision energies are needed to search for heavy hadron-like objects and investigate their properties.

   hep-phnucl-thJ.Phys.G(2017)·13 citations
5. 05*

   Azimuthal Asymmetry and Ratio $R=F_L/F_T$ as Probes of the Charm Content of the Proton

   N.Ya. Ivanov🇦🇲

   We study two experimental ways to measure the heavy-quark content of the proton: using the Callan-Gross ratio $R(x,Q^2)=F_L/F_T$ and/or azimuthal $\cos (2\phi )$ asymmetry in deep inelastic lepton-nucleon scattering. Our approach is based on the perturbative stability of the QCD predictions for these two quantities. We resume the mass logarithms of the type ${\alpha }_s\ln \left(Q^2/m^2\right)$ and conclude that heavy-quark densities in the nucleon can, in principle, be determined from data on the Callan-Gross ratio and/or azimuthal asymmetry. In particular, the charm content of the proton can be measured in future studies at the proposed Large Hadron-Electron (LHeC) and Electron-Ion (EIC) Colliders.

   hep-phJ.Contemp.Phys.(2012)·0 citations
6. 06*

   Discovery potential of Higgs boson pair production through 4$\ell$+$E/$ final states at a 100 TeV collider

   Xiaoran Zhao🇧🇪 · Qiang Li🇨🇳 · Zhao Li🇨🇳 · Qi-Shu Yan🇨🇳

   We explore the discovery potential of Higgs pair production at a 100 TeV collider via full leptonic mode. The same mode can be explored at the LHC when Higgs pair production is enhanced by new physics. We examine two types of fully leptonic final states and propose a partial reconstruction method. The reconstruction method can reconstruct some kinematic observables. It is found that the $m_{T2}$ variable determined by this reconstruction method and the reconstructed visible Higgs mass are important and crucial to discriminate the signal and background events. It is also noticed that a new variable, denoted as $\Delta m$ which is defined as the mass difference of two possible combinations, is very useful as a discriminant. We also investigate the interplay between the direct measurements of $t\bar{t}h$ couplings and other related couplings and trilinear Higgs coupling at hadron colliders and electron-positron colliders.

   hep-phCPC(2017)·12 citations
7. 07*

   Heavy quark potential with hyperscaling violation

   Zi-qiang Zhang🇨🇳 · Chong Ma🇨🇳 · De-fu Hou🇨🇳 · Gang Chen🇨🇳

   In this paper, we investigate the behavior of the heavy quark potential in the backgrounds with hyperscaling violation. The metrics are covariant under a generalized Lifshitz scaling symmetry with the dynamical Lifshitz parameter $z$ and hyperscaling violation exponent $\theta$. We calculate the potential for a certain range of $z$ and $\theta$ and discuss how it changes in the presence of the two parameters. Moreover, we add a constant electric field to the backgrounds and study its effects on the potential. It is shown that the heavy quark potential depends on the non-relativistic parameters. Also, the presence of the constant electric field tends to increase the potential.

   hep-phAdv.High Energy Phys.(2017)·7 citations
8. 08*

   Charged Q-ball Dark Matter from $B$ and $L$ direction

   Jeong-Pyong Hong🇯🇵 · Masahiro Kawasaki🇯🇵 · Masaki Yamada🇯🇵

   We consider nearly equal number of gauge mediation type charged (anti-) Q-balls with charge of ${\alpha }^{-1}\simeq 137$ well before the BBN epoch and discussed how they evolve in time. We found that ion-like objects with electric charges of $+O(1)$ are likely to become relics in the present universe, which we expect to be the dark matter. These are constrained by MICA experiment, where the trail of heavy atom-like or ion-like object in $10^9$ years old ancient mica crystals is not observed. We found that the allowed region for gauge mediation model parameter and reheating temperature have to be smaller than the case of the neutral Q-ball dark matter.

   hep-phJCAP(2016)·18 citations
9. 09*

   The leading twist light-cone distribution amplitudes for the S-wave and P-wave Bc mesons

   Ji Xu🇨🇳 · Deshan Yang🇨🇳

   The light-cone distribution amplitudes (LCDAs) serve as important non-perturbative inputs for the study of hard exclusive processes. In this paper, we calculate ten LCDAs at twist-2 for the S-wave and P-wave $B_c$ mesons up to the next-to-leading order (NLO) of the strong coupling ${\alpha }_s$ and leading order of the velocity expansion. Each one of these ten LCDAs is expressed as a product of a perturbatively calculable distribution and a universal NRQCD matrix-element. By use of the spin symmetry, only two NRQCD matrix-elements will be involved. The reduction of the number of non-perturbative inputs will improve the predictive power of collinear factorization.

   hep-phJHEP(2016)·10 citations
10. 10*

    Bose-Einstein correlations and ${\mathbf{v}}_{2n}$ and ${\mathbf{v}}_{2n-1}$ in hadron and nucleus collisions

    E. Gotsman (Tel Aviv U.)🇮🇱 · E.Levin (Tel Aviv U./UTFSM)🇮🇱 · U. Maor (Tel Aviv U.)🇮🇱

    We show that Bose-Einstein correlations of identical particles in hadron and nucleus high energy collisions, lead to long range rapidity correlations in the azimuthal angle. These correlations are inherent features of the CGC/saturation approach, however, their origin is more general than this approach. In framework of the proposed technique both even and odd $v_n$ occur naturally, independent of the type of target and projectile. We are of the opinion that it is premature to conclude that the appearance of azimuthal correlations are due to the hydrodynamical behaviour of the quark-gluon plasma.

    hep-phPRD(2017)·8 citations
11. 11*

    Comment on "Testing Planck-Scale Gravity with Accelerators"

    Tigran Kalaydzhyan🇺🇸

    We challenge the analysis and conclusions of the paper Phys. Rev. Lett. 109, 141103 (2012) by V. Gharibyan on the tests of Planck-scale gravity with accelerators. The main objective of the Comment is the observation that the explored domain of "quantum gravity" parameters is already ruled out experimentally from, e.g., absence of the vacuum Cherenkov radiation.

    hep-phgr-qchep-exhep-thPRL(2016)·2 citations
12. 12*

    Thermodynamics of quark matter with a chiral imbalance

    R. L. S. Farias🇧🇷 · Dyana C. Duarte🇧🇷 · Gastão Krein🇧🇷 · Rudnei O. Ramos🇧🇷

    We show how a scheme of rewriting a divergent momentum integral can conciliate results obtained with the Nambu--Jona-Lasinio model and recent lattice results for the chiral transition in the presence of a chiral imbalance in quark matter. Purely vacuum contributions are separated from medium-dependent regularized momentum integrals in such a way that one is left with ultraviolet divergent momentum integrals that depend on vacuum quantities only. The scheme is applicable to other commonly used effective models to study quark matter with a chiral imbalance, it allows us to identify the source of their difficulties in reproducing the qualitative features of lattice results, and enhances their predictability and uses in other applications.

    hep-phPRD(2016)·58 citations
13. 13*

    A First-Order Electroweak Phase Transition from Varying Yukawas

    Iason Baldes🇩🇪 · Thomas Konstandin🇩🇪 · Geraldine Servant🇩🇪

    We show that the dynamics responsible for the variation of the Yukawa couplings of the Standard Model fermions generically leads to a very strong first-order electroweak phase transition, assuming that the Yukawa couplings are large and of order 1 before the electroweak phase transition and reach their present value afterwards. There are good motivations to consider that the flavour structure could emerge during electroweak symmetry breaking, for example if the Froggatt-Nielsen field dynamics were linked to the Higgs field. In this paper, we do not need to assume any particular theory of flavour and show in a model-independent way how the nature of the electroweak phase transition is completely changed when the Standard Model Yukawas vary at the same time as the Higgs is acquiring its vacuum expectation value. The thermal contribution of the fermions creates a barrier between the symmetric and broken phase minima of the effective potential, leading to a first-order phase transition. This offers new routes for generating the baryon asymmetry at the electroweak scale, strongly tied to flavour models.

    hep-phPLB(2018)·68 citations
14. 14*

    Kaon regeneration

    Valeriy Nazaruk🇷🇺

    We have performed the calculation of kaon regeneration based on the exact solution of equations of motion. The result differs radically from the previous one.

    hep-phIJMPE(2016)·5 citations
15. 15*

    Collider Constraints and Prospects of a Scalar Singlet Extension to Higgs Portal Dark Matter

    Grace Dupuis🇨🇦

    This work considers an extension of the Standard Model (SM) Higgs sector by a real, scalar singlet field, including applicability to a dark matter (DM) model with the addition of a Yukawa coupling to a Dirac fermion. The collider signatures and constraints on the mixed two-Higgs scenario are determined, including limits from Higgs production signals and exclusion searches, as well as constraints arising from the Higgs total and invisible widths. As there is overwhelming Higgs data which is consistent with a SM scenario, the case in which an additional scalar has evaded detection is further explored in the context of Higgs precision measurement. The discovery reach and prospective signatures of the model at a proposed linear collider are investigated, with particular focus on the Higgs triple coupling, and di-Higgs production processes.

    hep-phJHEP(2016)·43 citations
16. 16*

    Bottom $(70,1^{-})$ baryon multiplet

    S.M. Gerasyuta🇷🇺 · E.E. Matskevich🇷🇺

    The masses of negative parity $(70,1^{-})$ bottom nonstrange baryons are calculated in the relativistic quark model. The relativistic three-quark equations of the $(70,1^{-})$ bottom baryon multiplet are derived in the framework of the dispersion relation technique. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitude are obtained. The masses of 21 baryons are predicted.

    hep-ph0 citations
17. 17*

    Dark matter scattering on electrons: Accurate calculations of atomic excitations and implications for the DAMA signal

    B. M. Roberts🇺🇸 · V. A. Dzuba🇦🇺 · V. V. Flambaum🇦🇺 · M. Pospelov🇨🇦 · Y. V. Stadnik🇦🇺

    We revisit the WIMP-type dark matter scattering on electrons that results in atomic ionization, and can manifest itself in a variety of existing direct-detection experiments. Unlike the WIMP-nucleon scattering, where current experiments probe typical interaction strengths much smaller than the Fermi constant, the scattering on electrons requires a much stronger interaction to be detectable, which in turn requires new light force carriers. We account for such new forces explicitly, by introducing a mediator particle with scalar or vector couplings to dark matter and to electrons. We then perform state of the art numerical calculations of atomic ionization relevant to the existing experiments. Our goals are to consistently take into account the atomic physics aspect of the problem (e.g., the relativistic effects, which can be quite significant), and to scan the parameter space: the dark matter mass, the mediator mass, and the effective coupling strength, to see if there is any part of the parameter space that could potentially explain the DAMA modulation signal. While we find that the modulation fraction of all events with energy deposition above 2 keV in NaI can be quite significant, reaching ~50%, the relevant parts of the parameter space are excluded by the XENON10 and XENON100 experiments.

    hep-phastro-ph.COhep-exphysics.atom-phPRD(2016)·81 citations
18. 18*

    Classical Electromagnetic Fields from Quantum Sources in Heavy-Ion Collisions

    Robert Holliday🇺🇸 · Ryan McCarty🇺🇸 · Balthazar Peroutka🇺🇸 · Kirill Tuchin🇺🇸

    Electromagnetic fields are generated in high energy nuclear collisions by spectator valence protons. These fields are traditionally computed by integrating the Maxwell equations with point sources. One might expect that such an approach is valid at distances much larger than the proton size and thus such a classical approach should work well for almost the entire interaction region in the case of heavy nuclei. We argue that, in fact, the contrary is true: due to the quantum diffusion of the proton wave function, the classical approximation breaks down at distances of the order of the system size. We compute the electromagnetic field created by a charged particle described initially as a Gaussian wave packet of width 1 fm and evolving in vacuum according to the Klein-Gordon equation. We completely neglect the medium effects. We show that the dynamics, magnitude and even sign of the electromagnetic field created by classical and quantum sources are different.

    hep-phnucl-thNPA(2017)·28 citations
19. 19*

    $\varphi$-meson production at forward/backward rapidity in high-energy nuclear collisions from a multiphase transport model

    Y. J. Ye🇨🇳 · J. H. Chen🇨🇳 · Y. G. Ma🇨🇳 · S. Zhang🇨🇳 · C. Zhong🇨🇳

    Within the framework of a multiphase transport model (AMPT), the $\varphi$-meson production is studied in d+Au collisions at \srt = {200} GeV in the forward (d-going, $1.2<y<2.2$) and backward (Au-going, $-2.2<y<-1.2$) direction. The AMPT model with string melting version (parton cascade turning-on) describes the experimental data well, while the pure hadronic transport scenario of the AMPT model underestimates the $\varphi$-meson production rate in comparison with the data. Detailed investigations including the rapidity, transverse momentum and collision system size dependencies of $\varphi$-meson nuclear modification factor indicate that a combination of the initial state effect and a follow-up parton cascade is required in the AMPT model to describe the data. Similar calculations are also present in p+Pb collisions at \srt = {5.02} TeV and p+p collisions at \srt = {2.76} TeV. The findings from a comparison of AMPT model study with the data are consistent with that at RHIC energy.

    ↳ nucl-thhep-phnucl-exPRC(2016)·4 citations
20. 20*

    Multiple Fields in Stochastic Inflation

    Hooshyar Assadullahi🇬🇧 · Hassan Firouzjahi🇮🇷 · Mahdiyar Noorbala🇮🇷 · Vincent Vennin🇬🇧 · David Wands🇬🇧

    Stochastic effects in multi-field inflationary scenarios are investigated. A hierarchy of diffusion equations is derived, the solutions of which yield moments of the numbers of inflationary $e$-folds. Solving the resulting partial differential equations in multi-dimensional field space is more challenging than the single-field case. A few tractable examples are discussed, which show that the number of fields is, in general, a critical parameter. When more than two fields are present for instance, the probability to explore arbitrarily large-field regions of the potential, otherwise inaccessible to single-field dynamics, becomes non-zero. In some configurations, this gives rise to an infinite mean number of $e$-folds, regardless of the initial conditions. Another difference with respect to single-field scenarios is that multi-field stochastic effects can be large even at sub-Planckian energy. This opens interesting new possibilities for probing quantum effects in inflationary dynamics, since the moments of the numbers of $e$-folds can be used to calculate the distribution of primordial density perturbations in the stochastic-$\delta N$ formalism.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2016)·94 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.