HEP Phenomenology·hep-ph

Fri·Nov 13, 2015Friday·November 13, 2015

30 papers—19 primary·11 cross-listed·reconstructed*

01*
Probing proton fluctuations with asymmetric rapidity correlations
Adam Bzdak🇵🇱 · Kevin Dusling🇺🇸
Intrinsic fluctuations of the proton saturation momentum generate asymmetric rapidity distributions on an event-by-event basis. We argue that the asymmetric component, $⟨ a_{1}^{2} ⟩$ , of the orthogonal polynomial decomposition of the two-particle rapidity correlation function is a sensitive probe to this distribution of fluctuations. We present a simple model connecting the experimentally measured $⟨ a_{1}^{2} ⟩$ to the variance, $σ$ , of the distribution of the logarithm of the proton saturation scale. We find that $σ \approx 0.5 - 1$ describes the asymmetric component of the rapidity correlations recently measured by the ATLAS collaboration.
hep-phnucl-thPRC(2016)·23 citations
02*
Higher Hybrid Bottomonia in an Extended Potential Model
Nosheen Akbar🇵🇰 · M. Atif Sultan🇵🇰 · Bilal Masud🇵🇰 · Faisal Akram🇵🇰
Using our extension of the quark potential model to hybrid mesons that fits well to the available lattice results, we now calculate the masses, radii, wave functions at origin, leptonic and two photon decay widths, E1 and M1 radiative transitions for a significant number of bottomonium mesons. These mesons include both conventional and hybrid ones with radial and angular excitations. Our numerical solutions of the Schrodinger equation are related to QCD through the Born-Oppenheimer approach. Relativistic corrections in masses and decay widths are also calculated by applying the leading order perturbation theory. The calculated results are compared with available experimental data and the theoretical results by other groups. We also identify the states of $Υ (10860)$ , $Υ (11020)$ , and $Y_{b} (10890)$ mesons by comparing their experimental masses and decay widths with our results.
hep-phPRD(2017)·25 citations
03*
The Higgs Boson at LHC and the Vacuum Stability of the Standard Model
E.A. Reyes Rojas🇨🇴
The main aim of this work is to study the conditions of absolute vacuum stability within the Standard Model (SM) by the knowledge of the behaviour of the Higgs quartic coupling up to high energy scales and using the new data on the Higgs mass given by ATLAS and CMS as an input parameter. The Higgs mass value observed by ATLAS and CMS leads to a negative value of the quartic coupling, making metastable the vacuum of the Standard Model, as it is seen by the renormalization group improved (RGI) effective potential. The stability status of SM crucially depends upon the precise values of the top and Higgs masses, a more precision determination of those masses and related uncertainties can modify drastically our conclusions about the SM stability properties. For this reason, we have computed the vacuum bubbles and the Higgs tadpole diagrams, at two-loop level of accuracy, in a renormalization scheme proposed by A. Sirlin and R. Zucchini, where the input parameters are obtained in terms of physical observables related with muon decay, and where the threshold effects are included. In particular, we focus on the analytic computation of the Higgs tadpoles contributions by two different methods. From one side we have computed the sum of the tadpoles as the first derivative of the two-loop Higgs 1PI effective potential in the Sirlin-Zucchini scheme, on the other side we have checked the obtained result toward the direct diagrammatic two- loop computation, by proposing a way of automatization of our procedure based on the generation of Feynman diagrams, reduction of their integrands and evaluation of scalar integrals and sum of all contributions in a non-redundant way. We used the code TARCER that implements the Tarasov method to reduce two-loop tensorial integrals.
hep-ph6 citations
04*
Strange and Charm Quark Spins from Anomalous Ward Identity
Ming Gong🇨🇳 · Yi-Bo Yang🇺🇸 · Jian Liang🇺🇸 · Andrei Alexandru🇺🇸 · Terrence Draper🇺🇸 · Keh-Fei Liu🇺🇸
We present a calculation of the strange and charm quark contributions to the nucleon spin from the anomalous Ward identity (AWI). It is performed with overlap valence quarks on 2+1-flavor domain-wall fermion gauge configurations on a $2 4^{3} \times 64$ lattice with the light sea mass at $m_{π} = 330$ MeV. To satisfy the AWI, the overlap fermion for the pseudoscalar density and the overlap Dirac operator for the topological density, which do not have multiplicative renormalization, are used to normalize the form factor of the local axial-vector current at finite $q^{2}$ . For the charm quark, we find that the negative pseudoscalar term almost cancels the positive topological term. For the strange quark, the pseudoscalar term is less negative than that of the charm. By imposing the AWI, the strange $g_{A} (q^{2})$ at $q^{2} = 0$ is obtained by a global fit of the pseudoscalar and the topological form factors, together with $g_{A} (q^{2})$ and the induced pseudoscalar form factor $h_{A} (q^{2})$ at finite $q^{2}$ . The chiral extrapolation to the physical pion mass gives $Δ s + Δ s ˉ = - 0.0403 (44) (78)$ .
hep-phhep-latPRD(2017)·25 citations
05*
Strong tW Scattering at the LHC
Jeff Asaf Dror🇺🇸 · Marco Farina🇺🇸 · Ennio Salvioni🇺🇸 · Javi Serra🇨🇭
Deviations of the top electroweak couplings from their Standard Model values imply that certain amplitudes for the scattering of third generation fermions and longitudinally polarized vector bosons or Higgses diverge quadratically with momenta. This high-energy growth is a genuine signal of models where the top quark is strongly coupled to the sector responsible for electroweak symmetry breaking. We propose to profit from the high energies accessible at the LHC to enhance the sensitivity to non-standard top- $Z$ couplings, which are currently very weakly constrained. To demonstrate the effectiveness of the approach, we perform a detailed analysis of $t W \to t W$ scattering, which can be probed at the LHC via $pp \to t t ˉ W j$ . By recasting a CMS analysis at 8 TeV, we derive the strongest direct bounds to date on the $Z tt$ couplings. We also design a dedicated search at 13 TeV that exploits the distinctive features of the $t t ˉ W j$ signal. Finally, we present other scattering processes in the same class that could provide further tests of the top-Higgs sector.
hep-phhep-exJHEP(2016)·118 citations
06*
Scrutinizing the Alignment Limit in Two-Higgs-Doublet Models. Part 2: $m_{H} = 125$ GeV
Jérémy Bernon🇫🇷 · John F. Gunion🇺🇸 · Howard E. Haber🇺🇸 · Yun Jiang🇩🇰 · Sabine Kraml🇫🇷
In the alignment limit of a multi-doublet Higgs sector, one of the Higgs mass eigenstates aligns in field space with the direction of the scalar field vacuum expectation values, and its couplings approach those of the Standard Model (SM) Higgs boson. We consider CP-conserving Two-Higgs-Doublet Models (2HDMs) of Type I and Type II near the alignment limit in which the heavier of the two CP-even Higgs bosons, $H$ , is the SM-like state observed with a mass of 125 GeV, and the couplings of $H$ to gauge bosons approach those of the SM. We review the theoretical structure and analyze the phenomenological implications of this particular realization of the alignment limit, where decoupling of the extra states cannot occur given that the lighter CP-even state $h$ must, by definition, have a mass below 125 GeV. For the numerical analysis, we perform scans of the 2HDM parameter space employing the software packages 2HDMC and Lilith, taking into account all relevant pre-LHC constraints, constraints from the measurements of the 125 GeV Higgs signal at the LHC, as well as the most recent limits coming from searches for heavy Higgs-like states. Implications for Run 2 at the LHC, including expectations for observing the other scalar states, are also discussed.
hep-phPRD(2016)·136 citations
07*
Constraints on Light Dark Matter from Single-Photon Decays of Heavy Quarkonium
Nicolas Fernandez🇺🇸 · Ilsoo Seong🇺🇸 · Patrick Stengel🇺🇸
We investigate constraints on the interactions of light dark matter with Standard Model quarks in a framework with effective contact operators mediating the decay of heavy flavor bound state quarkonium to dark matter and a photon. When considered in combination with decays to purely invisible final states, constraints from heavy quarkonium decays at high intensity electron-positron colliders can complement missing energy searches at high energy colliders and provide sensitivity to dark matter masses difficult to probe at direct and indirect detection experiments. We calculate the approximate limits on the branching fraction for $Υ (1 S)$ decays to dark matter and a photon. Given the approximate limits on the branching fractions for all dimension 6 or lower contact operators, we present the corresponding limits on the interaction strength for each operator and the inferred limits on dark matter-nucleon scattering. Complementary constraints on dark matter annihilation from gamma-ray searches from dwarf spheroidal galaxies are also considered.
hep-phastro-ph.COhep-exPRD(2016)·14 citations
08*
sin $^{2} θ_{W}$ theory and new physics
Hye-Sung Lee🇰🇷
After briefly discussing the importance of the precise measurement of the weak mixing angle, we discuss the implication of the dark Z on the low-Q^2 parity tests. The dark Z is a very light (roughly, MeV - GeV scale) gauge boson, which couples to the electromagnetic current as well as the weak neutral current.
hep-phJ.Univ.Sci.Tech.China(2016)·8 citations
09*
Study of entropy production in Yang-Mills theory with use of Husimi function
Hidekazu Tsukiji🇯🇵 · Hideaki Iida🇯🇵 · Teiji Kunihiro🇯🇵 · Akira Ohnishi🇯🇵 · Toru T. Takahashi🇯🇵
Understanding the thermalization process in a pure quantum system is a challenge in theoretical physics. In this work, we explore possible thermalization mechanism in Yang-Mills(YM) theory by using a positive semi-definite quantum distribution function called a Husimi function which is given by a coarse graining of the Wigner function within the minimum uncertainty. Then entropy is defined in terms of the Husimi function, which is called the Husimi-Wehrl(HW) entropy. We propose two numerical methods to calculate the HW entropy. We find that it is feasible to apply the semi-classical approximation with the use of classical YM equation. It should be noted that the semi-classical approximation is valid in the systems of physical interest including the early stage of heavy-ion collisions. Using a product ansatz for the Husimi function, which is confirmed to reproduce the HW entropy within 20% error (overestimate) for a few-body quantum system, we succeed in a numerical evaluation of HW entropy of YM fields and show that it surely has a finite value and increases in time.
hep-phnucl-thquant-phPoS(2016)·0 citations
10*
Rare radiative decays of the $B_{c}$ meson
Wan-Li Ju🇨🇳 · Tianhong Wang🇨🇳 · Yue Jiang🇨🇳 · Han Yuan🇨🇳 · Guo-Li Wang🇨🇳
In this paper, we study the rare radiative processes $B_{c} \to D_{s J}^{(*)} γ$ within the Standard Model, where $D_{s J}^{(*)}$ stands for the meson $D_{s}^{*}$ ,~ $D_{s 1} (2460, 2536)$ or ~ $D_{s 2}^{*} (2573)$ . During the investigations, we consider the contributions from the penguin, annihilation, color-suppressed and color-favored cascade diagrams. Our results show that: 1) the penguin and annihilation contributions are dominant in the branching fractions; 2) for the processes $B_{c} \to D_{s}^{*} γ$ and $B_{c} \to D_{s 1} (2460, 2536) γ$ , the effects from the color-suppressed and color-favored cascade diagrams are un-negligible.
hep-phhep-exJ.Phys.G(2016)·3 citations
11*
Neutrino Mass and Mixing in the Seesaw Playground
Stephen F. King🇬🇧
We discuss neutrino mass and mixing in the framework of the classic seesaw mechanism, involving right-handed neutrinos with large Majorana masses, which provides an appealing way to understand the smallness of neutrino masses. However, with many input parameters, the seesaw mechanism is in general not predictive. We focus on natural implementations of the seesaw mechanism, in which large cancellations do not occur, where one of the right handed neutrinos is dominantly responsible for the atmospheric neutrino mass, while a second right-handed neutrino accounts for the solar neutrino mass, leading to an effective two right-handed neutrino model. We discuss recent attempts to predict lepton mixing and CP violation within such natural frameworks, focussing on the Littlest Seesaw and its distinctive predictions.
hep-phNPB(2016)·28 citations
12*
Leptogenesis parametrized by lepton mass matrices
Pei-Hong Gu🇨🇳 · Xiao-Gang He🇹🇼
The conventional seesaw-leptogenesis can simultaneously explain the suppression of neutrino masses and the generation of cosmic baryon asymmetry, but usually cannot predict an unambiguous relation between these two sectors. In this work we shall demonstrate a novel left-right symmetric scenario, motivated to solve the strong CP problem by parity symmetry, where the present baryon asymmetry is determined by three charged lepton masses and a seesaw-suppressed hermitian Dirac neutrino mass matrix up to an overall scale factor. To produce the observed baryon asymmetry, this scenario requires that the neutrinos must have a normal hierarchical mass spectrum and their mixing matrix must contain a sizable Dirac CP phase. Our model can be tested in neutrino oscillation and neutrinoless double beta decay experiments.
hep-phEPJC(2016)·6 citations
13*
Predictions for Neutrinoless Double-Beta Decay in the 3+1 Sterile Neutrino Scenario
C. Giunti🇮🇹 · E. M. Zavanin🇧🇷
In this proceeding we present predictions of the effective Majorana mass $∣ m_{β β} ∣$ in neutrinoless double- $β$ decay for the standard $3 ν$ mixing case and for the 3+1 neutrino mixing case indicated by the short-baseline anomalies. We have taken into account the uncertainties of the neutrino mixing parameters determined by oscillation experiments. We obtained that the predictions for $∣ m_{β β} ∣$ in the cases of $3 ν$ and 3+1 mixing are quite different, in agreement with previous discussions in the literature, and that future measurements of neutrinoless double- $β$ decay and the total mass of the three lightest neutrinos in cosmological experiments may distinguish the $3 ν$ and 3+1 cases if the mass ordering is determined by oscillation experiments.
hep-phJ.Phys.Conf.Ser.(2016)·3 citations
14*
Displaced lepton flavour violating signatures of right-handed sneutrinos in $U (1)^{'}$ supersymmetric models
Priyotosh Bandyopadhyay🇮🇹
We consider a $U (1)^{'}$ extended supersymmetric model with a right-handed neutrino superfield which can generate light neutrino mass by Type I seesaw mechanism. The lighter superpartner of the right-handed neutrino could be the scalar dark matter. These right-handed sneutrinos can come from the decay of $Z^{'} ~$ , superpartner of the extra gauge boson $Z^{'}$ . Left-right handed sneutrino mixings affect their decays further, giving rise to displaced "lepton flavour violating" signatures. A wino-like chargino NLSP (next to lightest supersymmetric particle) creates even more interesting decay topology. We investigate such displaced multi-leptonic final states with "lepton flavour violation" from the supersymmetric cascade decays of third generation squarks at the LHC.
hep-phJHEP(2017)·9 citations
15*
Composite resonances and their impact on the EW chiral Lagrangian
J.J. Sanz-Cillero🇪🇸
In this talk we study the low-energy effective couplings generated by strongly-coupled electroweak models that contain heavy composite resonances. Invariance under $S U (2)_{L} \times S U (2)_{R}$ is a key ingredient in the construction of the resonance action. For simplicity, in these proceedings we focus our attention on the impact of a heavy colourless vector V, which transforms as a triplet under the custodial group. More precisely, we study the couplings that are relevant for the vector form-factors of the L+R current into two electroweak Goldstones and into two Standard Model fermions, which contribute to the oblique parameters S and T and the anomalous $Z \to f f ˉ$ couplings, respectively. Our predictions are compatible with bounds from direct and indirect searches for Mv > 1.5 TeV. Finally, although we consider an antisymmetric tensor formalism to describe the vector resonance, we derive the equivalent action in the Proca four-vector representation and show that the predictions for low-energy couplings and form-factors are identical, as expected.
hep-phPoS(2015)·0 citations
16*
Radial Meson Excitations and Abelian Self-Dual Gluon Fields
Sergei N. Nedelko🇷🇺 · Vladimir E. Voronin🇷🇺
We briefly review motivation and results of the approach to QCD vacuum as a medium describable in terms of statistical ensemble of almost everywhere constant Abelian (anti-)self-dual gluon fields. An overview of the hadronization formalism based on this ensemble is presented. New results for radial excitations of light, heavy-light mesons and heavy quarkonia are presented. A possible interrelation between the present approach and holographic QCD with harmonic confinement is outlined.
hep-phInt.J.Mod.Phys.Conf.Ser.(2015)·1 citation
17*
QCD running in neutrinoless double beta decay: Short-range mechanisms
M. González🇨🇱 · M. Hirsch🇪🇸 · S.G. Kovalenko🇨🇱
The decay rate of neutrinoless double beta ( $0 ν β β$ ) decay contains terms from heavy particle exchange, which lead to dimension-9 (d=9) six fermion operators at low energies. Limits on the coefficients of these operators have been derived previously neglecting the running of the operators between the high-scale, where they are generated, and the energy scale of double beta decay, where they are measured. Here we calculate the leading order QCD corrections to all possible d=9 operators contributing to the $0 ν β β$ amplitude and use RGE running to calculate 1-loop improved limits. Numerically, QCD running changes limits by factors of the order of or larger than typical uncertainties in nuclear matrix element calculations. For some specific cases, operator mixing in the running changes limits even by up to two orders of magnitude. Our results can be straightforwardly combined with new experimental limits or improved nuclear matrix element calculations to re-derive updated limits on all short-range contributions to $0 ν β β$ decay.
hep-phhep-exnucl-exnucl-thPRD(2016)·41 citations
18*
Testing the electroweak phase transition and electroweak baryogenesis at the LHC and a circular electron-positron collider
Fa Peng Huang🇨🇳 · Pei-Hong Gu🇨🇳 · Peng-Fei Yin🇨🇳 · Zhao-Huan Yu🇨🇳 · Xinmin Zhang🇨🇳
We study the collider phenomenology of the electroweak phase transition and electroweak baryogenesis in the framework of the effective field theory. Our study shows that the effective theory using the dimension-6 operators can enforce strong first order phase transition and provide sizable CP violation to realize a successful electroweak baryogenesis. Such dimension-6 operators can induce interesting Higgs phenomenology that can be verified at colliders such as the LHC and the planning CEPC. We then demonstrate that this effective theory can originate from vector-like quarks and the triplet Higgs.
hep-phPRD(2016)·89 citations
19*
Introducing Loopedia
Viktor Papara🇩🇪
Loopedia is a new project for a public database of loop integrals. After stating the goals and desired properties of the project, two possible ways to characterize Feynman graphs are explained here: the Adjacency List and the Nickel Index. Furthermore, a first version of the Loopedia website is presented. It allows for automatic graph generation and the conversion from Adjacency List to Nickel Index.
hep-phActa Phys.Polon.B(2015)·0 citations
20*
Photon mass as a probe to extra dimensions
G. Alencar🇧🇷 · C. R. Muniz🇧🇷 · R. R. Landim🇧🇷 · I. C. Jardim🇧🇷 · R. N. Costa Filho🇧🇷
In this manuscript we show that the geometrical localization mechanism implies a four dimensional mass for the photon. The consistence of the model provides a mass given exactly by $m_{γ} = R /4$ where $R$ is the Ricci scalar. As a consequence, the cosmological photon has a mass related to the vacuum solution of the Einstein equation. At the present age of the universe we have a dS vacuum with $R = 4Λ$ , where Lambda is a positive cosmological constant. With this we find that $m_{γ} \approx 2 \times 1 0^{- 69}$ kg, which is below the present experimental upper bounds, and such correction may be observed in the next years with more precise measurements. By considering the value of $R$ inside some astrophysical sources and environments we find that the bound is also satisfied. The experimental verification of this mass, beyond pointing to the existence of extra dimensions, would imply in a fundamental change in cosmology, astrophysics and in particle physics since the same mechanism is valid for non-abelian gauge fields.
↳ hep-thgr-qchep-phPLB(2016)·24 citations
21*
Bayesian parameter estimation for effective field theories
S. Wesolowski🇺🇸 · N. Klco🇺🇸 · R.J. Furnstahl🇺🇸 · D.R. Phillips🇺🇸 · A. Thapaliya🇺🇸
We present procedures based on Bayesian statistics for estimating, from data, the parameters of effective field theories (EFTs). The extraction of low-energy constants (LECs) is guided by theoretical expectations in a quantifiable way through the specification of Bayesian priors. A prior for natural-sized LECs reduces the possibility of overfitting, and leads to a consistent accounting of different sources of uncertainty. A set of diagnostic tools are developed that analyze the fit and ensure that the priors do not bias the EFT parameter estimation. The procedures are illustrated using representative model problems, including the extraction of LECs for the nucleon mass expansion in SU(2) chiral perturbation theory from synthetic lattice data.
↳ nucl-thhep-phnucl-exphysics.data-anJ.Phys.G(2016)·145 citations
22*
A Feynman Integral and its Recurrences and Associators
Georg Puhlfuerst🇩🇪 · Stephan Stieberger🇩🇪
We determine closed and compact expressions for the epsilon-expansion of certain Gaussian hypergeometric functions expanded around half-integer values by explicitly solving for their recurrence relations. This epsilon-expansion is identified with the normalized solution of the underlying Fuchs system of four regular singular points. We compute its regularized zeta series (giving rise to two independent associators) whose ratio gives the epsilon-expansion at a specific value. Furthermore, we use the well known one-loop massive bubble integral as an example to demonstrate how to obtain all-order epsilon-expansions for Feynman integrals and how to construct representations for Feynman integrals in terms of generalized hypergeometric functions. We use the method of differential equations in combination with the recently established general solution for recurrence relations with non-commutative coefficients.
↳ hep-thhep-phmath.NTNPB(2016)·8 citations
23*
Effective field theory of dissipative fluids
Michael Crossley🇺🇸 · Paolo Glorioso🇺🇸 · Hong Liu🇺🇸
We develop an effective field theory for dissipative fluids which governs the dynamics of long-lived gapless modes associated with conserved quantities. The resulting theory gives a path integral formulation of fluctuating hydrodynamics which systematically incorporates nonlinear interactions of noises. The dynamical variables are mappings between a "fluid spacetime" and the physical spacetime and an essential aspect of our formulation is to identify the appropriate symmetries in the fluid spacetime. The theory applies to nonlinear disturbances around a general density matrix. For a thermal density matrix, we require an additional $Z_{2}$ symmetry, to which we refer as the local KMS condition. This leads to the standard constraints of hydrodynamics, as well as a nonlinear generalization of the Onsager relations. It also leads to an emergent supersymmetry in the classical statistical regime, and a higher derivative deformation of supersymmetry in the full quantum regime.
↳ hep-thcond-mat.stat-mechgr-qchep-ph+2JHEP(2017)·356 citations
24*
Nonperturbative Regulator for Chiral Gauge Theories?
Dorota M. Grabowska🇺🇸 · David B. Kaplan🇺🇸
We propose a nonperturbative gauge invariant regulator for d-dimensional chiral gauge theories on the lattice. The method involves simulating domain wall fermions in d + 1 dimensions with quantum gauge fields that reside on one d-dimensional surface and are extended into the bulk via gradient flow. The result is a theory of gauged fermions plus mirror fermions, where the mirror fermions couple to the gauge fields via a form factor that becomes exponentially soft with the separation between domain walls. The resultant theory has a local d-dimensional interpretation only if the chiral fermion representation is anomaly free. A physical realization of this construction would imply the existence of mirror fermions in the standard model that are invisible except for interactions induced by vacuum topology, and which could gravitate differently than conventional matter.
↳ hep-lathep-phhep-thPRL(2016)·54 citations
25*
Effects of higher dimension operators on the Standard Model Higgs sector
Oscar Akerlund🇨🇭 · Philippe de Forcrand🇨🇭 · Jakob Steinbauer🇨🇭
We study the effect of higher dimension operators on the electroweak finite temperature phase transition in two sectors of the Standard Model. Firstly, the Higgs-Yukawa sector, consisting of the Higgs doublet and the massive Standard Model fermions, is studied with an approximate method, Extended Mean Field Theory. Secondly, the gauge-Higgs sector, consisting of the Higgs doublet and the gauge fields of the weak interaction, is studied using Monte Carlo simulations. In both cases we find that a cutoff scale of around 1.5 TeV is needed to make the electroweak phase transition first order at the experimental value of the Higgs boson mass, which is a requirement for making electroweak baryogenesis viable.
↳ hep-lathep-phPoS(2016)·6 citations
26*
Linear and cubic response to the initial eccentricity in heavy-ion collisions
Jacquelyn Noronha-Hostler🇺🇸 · Li Yan🇫🇷 · Fernando G. Gardim🇧🇷 · Jean-Yves Ollitrault🇫🇷
We study the relation between elliptic flow, $v_{2}$ and the initial eccentricity, $ε_{2}$ , in heavy-ion collisions, using hydrodynamic simulations. Significant deviations from linear eccentricity scaling are seen in more peripheral collisions. We identify the mechanism responsible for these deviations as a cubic response, which we argue is a generic property of the hydrodynamic response to the initial density profile. The cubic response increases elliptic flow fluctuations, thereby improving agreement of initial condition models with experimental data.
↳ nucl-thhep-phnucl-exPRC(2016)·143 citations
27*
On the nature of an emergent symmetry in QCD
Thomas D. Cohen🇺🇸
Remarkable symmetry properties appear to arise in lattice calculations of correlation functions in which the lowest-lying eigenmodes of the Dirac operator in quark propagators are removed by hand. The Banks-Casher relation ties the chiral condensate to the density of low lying modes; thus, it is plausible that removal of such modes could lead to a regime where spontaneous chiral symmetry breaking does not occur. Surprising, a pattern of identical correlation functions was observed that is larger than can be explained by a restoration of chiral symmetry. This suggests that a larger symmetry---one that is not present in the QCD lagrangian---emerges when these modes are removed. Previously it was argued that this emergent symmetry was SU(4). However, when the low-lying modes are removed, the correlation functions of sources in the SU(4) 15-plet of spin-1 mesons appear to coincide with the correlation function of the SU(4) singlet. A natural explanation for this is an emergent symmetry larger than SU(4). In this work, it is shown that there exists no continuous symmetry whose generators in the field theory are spatial integrals of local operators that can account for the full pattern of identical correlation functions unless the apparent coincidence of the singlet channel with the 15-plet is accidental.
↳ hep-lathep-phhep-thnucl-thPRD(2016)·13 citations
28*
Holography for Heavy Quarks and Mesons at Finite Chemical Potential
Carlo Ewerz🇩🇪 · Ling Lin🇩🇪 · Andreas Samberg🇩🇪 · Konrad Schade🇩🇪
We study the properties of heavy quarks as probes of strongly coupled plasmas with and without chemical potential by means of the gauge/gravity (AdS/CFT) duality. We compute the screening distance of a heavy quark-antiquark pair, its free energy, and the running coupling in large classes of non-conformal models arising as deformations of pure AdS space. We further investigate the energy loss of a heavy quark moving on a circular orbit as an example of an accelerated motion. These observables exhibit universal features independent of the deformation, pointing to strong-coupling universality. Our results should be relevant for processes involving heavy quarks and their bound states in the quark-gluon plasma, including the case of finite net baryon density.
↳ hep-thhep-phPoS(2015)·5 citations
29*
Gluon contribution to open heavy-meson production in heavy-ion collisions
Shanshan Cao🇺🇸 · Guang-You Qin🇨🇳 · Xin-Nian Wang🇨🇳
A sizable contribution to heavy quark production in high-energy hadronic and nuclear collisions comes from heavy quark-antiquark pair production from gluon splitting during the parton shower evolution. We investigate the effect of gluon-medium interaction on open heavy flavor spectra in ultra-relativistic heavy-ion collisions. The interaction of hard gluons and heavy quarks with the hot QCD medium is simulated by utilizing a Langevin transport model that simultaneously incorporates contributions from collisional and radiative processes. It is found that while the gluon splitting channel has quite an important contribution to the single $D$ meson production cross section, its influence on the final heavy meson nuclear modification turns out to be quite modest because the average lifetime of hard gluons is short before splitting into heavy quark-antiquark pairs during the evolution and propagation of the parton shower.
↳ nucl-thhep-phPRC(2016)·9 citations
30*
General form of entropy on the horizon of the universe in entropic cosmology
Nobuyoshi Komatsu🇯🇵 · Shigeo Kimura🇯🇵
Entropic cosmology assumes several forms of entropy on the horizon of the universe, where the entropy can be considered to behave as if it were related to the exchange (the transfer) of energy. To discuss this exchangeability, the consistency of the two continuity equations obtained from two different methods is examined, focusing on a homogeneous, isotropic, spatially flat, and matter-dominated universe. The first continuity equation is derived from the first law of thermodynamics, whereas the second equation is from the Friedmann and acceleration equations. To study the influence of forms of entropy on the consistency, a phenomenological entropic-force model is examined, using a general form of entropy proportional to the $n$ -th power of the Hubble horizon. In this formulation, the Bekenstein entropy (an area entropy), the Tsallis--Cirto black-hole entropy (a volume entropy), and a quartic entropy are represented by $n = 2$ , $3$ , and $4$ , respectively. The two continuity equations for the present model are found to be consistent with each other, especially when $n = 2$ , i.e., the Bekenstein entropy. The exchange of energy between the bulk (the universe) and the boundary (the horizon of the universe) should be a viable scenario consistent with the holographic principle.
↳ gr-qcastro-ph.COhep-phPRD(2016)·69 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.