arXiv subjects

Shuzhe Shi

Publications and source records attributed to Shuzhe Shi.

At least 91 records · Page 5Linked to original sources

arXiv2018

Examination of the observability of a chiral magnetically-driven charge-separation difference in collisions of the $\mathrm{^{96}_{44}Ru +\, ^{96}_{44}Ru}$ and $\mathrm{^{96}_{40}Zr +\, ^{96}_{40}Zr}$ isobars at energies available at RHIC

Anomalous Viscous Fluid Dynamics (AVFD) model calculations for $\mathrm{^{96}_{44}Ru +\, ^{96}_{44}Ru}$ and $\mathrm{^{96}_{40}Zr +\, ^{96}_{40}Zr}$ collisions ($\sqrt{s_{\rm NN}} = 200$ GeV) are used in concert with a charge-sensitive correlator, to test its ability to detect and characterize the charge separation difference expected from the Chiral Magnetic Effect (CME) in these isobaric collisions. The tests indicate a larger charge separation for $\mathrm{^{96}_{44}Ru +\, ^{96}_{44}Ru}$ than for $\mathrm{^{96}_{40}Zr +\, ^{96}_{40}Zr}$ collisions, and a discernible CME-driven difference of $\sim 10$\% in the presence of realistic non-CME backgrounds. They also indicate a strategy for evaluating the relative influence of the background correlations, present for each isobar. These results suggest that charge separation measurements for these isobaric species could serve to further constrain unambiguous identification and characterization of the CME in upcoming measurements at RHIC.

nucl-ex↗

arXiv2018

Probing the Color Structure of the Perfect QCD Fluids via Soft-Hard-Event-by-Event Azimuthal Correlations

We develop a comprehensive dynamical framework, CIBJET, to calculate on an event-by-event basis the dependence of correlations between soft ($p_T<2$ Gev) and hard ($p_T> 10$ Gev) azimuthal flow angle harmonics on the color composition of near-perfect QCD fluids produced in high energy nuclear collisions at RHIC and LHC. CIBJET combines consistently predictions of event-by-event VISHNU2+1 viscous hydrodynamic fluid fields with CUJET3.1 predictions of event-by-event jet quenching. We find that recent correlation data favor a temperature dependent color composition including bleached chromo-electric $q(T)+g(T)$ components and an emergent chromo-magnetic degrees of freedom $m(T)$ consistent with non-perturbative lattice QCD information in the confinement/deconfinement temperature range.

hep-ph↗

arXiv2018

Chiral Magnetic Effect in Isobaric Collisions from Anomalous-Viscous Fluid Dynamics (AVFD)

The isobaric collision experiment at RHIC provides the unique opportunity to detect the possible signal of Chiral Magnetic Effect (CME) in heavy ion collisions. The idea is to contrast the correlation observables of the two colliding systems that supposedly have identical flow-driven background contributions while quite different CME signal contributions due to the 10% variation in their nuclear charge and thus magnetic field strength. With the recently developed quantitative simulation tool for computing CME signal, the Anomalous-Viscous Fluid Dynamics (AVFD), we demonstrate that a joint (multiplicity + elliptic-flow) event selection is crucial for this purpose. We further propose to use the absolute difference between RuRu and ZrZr events (after using identical event selection) for detecting CME signal and make predictions for the correlation observables.

hep-ph↗

arXiv2018

Complete and Consistent Chiral Transport from Wigner Function Formalism

Recently there has been significant interest in understanding the macroscopic quantum transport in a many-body system of chiral fermions. A natural framework for describing such a system which is generally out of equilibrium, is the transport equation for its phase space distribution function. In this paper, we obtain a complete solution of the covariant chiral transport for massless fermions, by starting from the general Wigner function formalism and carrying out a complete and consistent semiclassical expansion up to $\hat{\mathbf{O}}(\hbar)$ order. In particular, we clarify certain subtle and confusing issues surrounding the Lorentz non-invariance and frame dependence associated with the 3D chiral kinetic theory. We prove that such frame dependence is uniquely and completely fixed by an unambiguous definition of the $\hat{\mathbf{O}}(\hbar)$ correction to the distribution function in each reference frame.

hep-th↗

arXiv2018

Viscous effects on the dynamical evolution of QCD matter during the first-order confinement phase transition in heavy-ion collisions

We investigate viscous effects on the dynamical evolution of QCD matter during the first-order phase transition, which may happen in heavy-ion collisions. We first obtain the first-order phase transition line in the QCD phase diagram under the Gibbs condition by using the MIT bag model and the hadron resonance gas model for the equation of state of partons and hadrons. The viscous pressure, which corresponds to the friction in the energy balance, is then derived from the energy and net baryon number conservation during the phase transition. We find that the viscous pressure relates to the thermodynamic change of the two-phase state and thus affects the timescale of the phase transition. Numerical results are presented for demonstrations.

hep-ph↗

arXiv2018

A New Correlator to Detect and Characterize the Chiral Magnetic Effect

A charge-sensitive in-event correlator is proposed and tested for its efficacy to detect and characterize charge separation associated with the Chiral Magnetic Effect (CME) in heavy ion collisions. Tests, performed with the aid of two reaction models, indicate discernible responses for background- and CME-driven charge separation, relative to the second- ($Ψ_{2}$) and third-order ($Ψ_{3}$) event planes, which could serve to identify the CME. The tests also indicate a degree of sensitivity which would enable robust characterization of the CME via Anomalous Viscous Fluid Dynamics (AVFD) model comparisons.

physics.data-an↗

arXiv2018

Sequential Coalescence with Charm Conservation in High Energy Nuclear Collisions

Heavy quarks are initially produced in nuclear collisions and the number is conserved during the evolution of the system. We establish a sequential coalescence model with charm conservation and apply it to charmed hadron production at RHIC and LHC energies. The charm conservation enhances the earlier formed hadrons and reduces the later formed ones, which leads to a $D_s/D^0$ enhancement and a $Λ_c/D^0$ suppression. The mass dependence of the sequential hadron formation provides us a new tool for studying the quark-gluon plasma hadronization in high energy nuclear collisions.

hep-ph↗

arXiv2018

Anomalous Chiral Transport in Heavy Ion Collisions from Anomalous-Viscous Fluid Dynamics

Chiral anomaly is a fundamental aspect of quantum theories with chiral fermions. How such microscopic anomaly manifests itself in a macroscopic many-body system with chiral fermions, is a highly nontrivial question that has recently attracted significant interest. As it turns out, unusual transport currents can be induced by chiral anomaly under suitable conditions in such systems, with the notable example of the Chiral Magnetic Effect (CME) where a vector current (e.g. electric current) is generated along an external magnetic field. A lot of efforts have been made to search for CME in heavy ion collisions, by measuring the charge separation effect induced by the CME transport. A crucial challenge in such effort, is the quantitative prediction for the CME signal. In this paper, we develop the Anomalous-Viscous Fluid Dynamics (AVFD) framework, which implements the anomalous fluid dynamics to describe the evolution of fermion currents in QGP, on top of the neutral bulk background described by the VISH2+1 hydrodynamic simulations for heavy ion collisions. With this new tool, we quantitatively and systematically investigate the dependence of the CME signal to a series of theoretical inputs and associated uncertainties. With realistic estimates of initial conditions and magnetic field lifetime, the predicted CME signal is quantitatively consistent with measured change separation data in 200GeV Au-Au collisions. Based on analysis of Au-Au collisions, we further make predictions for the CME observable to be measured in the planned isobaric (Ru-Ru v.s. Zr-Zr ) collision experiment, which could provide a most decisive test of the CME in heavy ion collisions.

nucl-th↗

arXiv2018

Out-of-Equilibrium Chiral Magnetic Effect from Chiral Kinetic Theory

Recently there has been significant interest in the macroscopic manifestation of chiral anomaly in many-body systems of chiral fermions. A notable example is the Chiral Magnetic Effect (CME). Enthusiastic efforts have been made to search for the CME in the quark-gluon plasma created in heavy ion collisions. A crucial challenge is that the extremely strong magnetic field in such collisions may last only for a brief moment and the CME current may have to occur at so early a stage that the quark-gluon matter is still far from thermal equilibrium. This thus requires modeling of the CME in an out-of-equilibrium setting. With the recently developed theoretical tool of chiral kinetic theory, we make a first phenomenological study of the CME-induced charge separation during the pre-thermal stage in heavy ion collisions. The effect is found to be very sensitive to the time dependence of the magnetic field and also influenced by the initial quark momentum spectrum as well as the relaxation time of the system evolution toward thermal equilibrium. Within the present approach, such pre-thermal charge separation is found to be modest.

hep-ph↗

arXiv2017

Searching for the Subatomic Swirls in the CuCu and CuAu Collisions

Recently the STAR Collaboration discovered the "subatomic swirls", that is, the most vortical fluid flow structures in the quark-gluon plasma produced via the AuAu collisions at the Relativistic Heavy Ion Collider (RHIC). Published in Nature and featured as a cover story, this discovery attracted significant interest and generated wide enthusiasm. For such an important finding, it is crucial to look for independent evidences of confirmation and to critically test the current interpretation of the global polarization measurement. We suggest that the CuCu and CuAu colliding systems at RHIC provide such opportunity. Interestingly, our calculations reveal that the fluid vorticity in the CuCu or CuAu collision is comparable to that in the AuAu Collision. Surprisingly, we find the computed $Λ$ hyperon polarization effect is stronger in the CuCu and CuAu systems than the AuAu system at the same collisional beam energy and centrality class, with an interesting hierarchy CuCu $>$ CuAu $>$ AuAu due to interplay between $Λ$ production timing and the time evolution of the vorticity. These predictions can be readily tested by experimental data.

nucl-th↗

arXiv2017

Quantification of Chiral Magnetic Effect from Event-by-Event Anomalous-Viscous Fluid Mechanics

Chiral Magnetic Effect (CME) is the macroscopic manifestation of the fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as anomalous transport current in hydrodynamic framework. Experimental observation of CME is of great interest and significant efforts have been made to look for its signals in heavy ion collisions. Encouraging evidence of CME-induced charge separation has been reported from both RHIC and LHC, albeit with ambiguity due to potential background contributions. Crucial for addressing such issue, is the need of quantitative predictions for both CME signal and the non-CME background consistently, with sophisticated modeling tool. In this contribution we report a recently developed Anomalous Viscous Fluid Dynamics (AVFD) framework, which simulates the evolution of fermion currents in QGP on top of the data-validated VISHNU bulk hydro evolution. In particular, this framework has been extended to event-by-event simulations with proper implementation of known flow-driven background contributions. We report quantitative results from such simulations and evaluate the implications for interpretations of current experimental measurements. Finally we give our prediction for the CME signal in upcoming isobaric collisions.

nucl-th↗

arXiv2017

Quantifying Chiral Magnetic Effect from Anomalous-Viscous Fluid Dynamics

The Chiral Magnetic Effect (CME) is a macroscopic manifestation of fundamental chiral anomaly in a many-body system of chiral fermions, and emerges as anomalous transport current in the fluid dynamics framework. Experimental observation of CME is of great interest and has been reported in Dirac and Weyl semimetals. Significant efforts have also been made to look for CME in heavy ion collisions. Critically needed for such search, is the theoretical prediction for CME signal. In this paper we report a first quantitative modeling framework, the Anomalous Viscous Fluid Dynamics (AVFD), which computes the evolution of fermion currents on top of realistic bulk evolution in heavy ion collisions and simultaneously accounts for both anomalous and normal viscous transport effects. The AVFD allows a quantitative understanding of the generation and evolution of CME-induced charge separation during hydrodynamic stage as well as its dependence on theoretical ingredients. With reasonable estimates of key parameters, the AVFD simulations provide the first phenomenologically successful explanation of the measured signal in 200AGeV AuAu collisions.

nucl-th↗

arXiv2017

A Unified Description for Comprehensive Sets of Jet Energy Loss Observables with CUJET3

Jet energy loss in heavy ion collisions, as quantified by the traditional observable of high $p_T$ hadron's nuclear modification factor $R_{AA}$, provides highly informative "imaging" of the hot medium created in heavy ion collisions. There are now comprehensive sets of available data, from average suppression to azimuthal anisotropy, from light to heavy flavors, from RHIC 200GeV to LHC 2.76TeV as well as 5.02TeV collisions. A unified description of such comprehensive data presents a stringent vetting of any viable model for jet quenching phenomenology. In this contribution we report such a systematic and successful test of CUJET3, a jet energy loss simulation framework built upon a nonperturbative microscopic model for the hot medium as a semi-quark-gluon-monopole plasma (sQGMP) which integrates two essential elements of confinement, i.e. the Polyakov-loop suppression of quarks/gluons and emergent magnetic monopoles.

hep-ph↗

arXiv2017

Quantifying the Chiral Magnetic Effect from Anomalous-Viscous Fluid Dynamics

In this contribution we report a recently developed Anomalous-Viscous Fluid Dynamics (AVFD) framework, which simulates the evolution of fermion currents in QGP on top of the bulk expansion from data-validated VISHNU hydrodynamics. With reasonable estimates of initial conditions and magnetic field lifetime, the predicted CME signal is quantitatively consistent with change separation measurements in 200GeV Au-Au collisions at RHIC. We further develop the event-by-event AVFD simulations that allow direct evaluation of two-particle correlations arising from CME signal as well as the non-CME backgrounds. Finally we report predictions from AVFD simulations for the upcoming isobaric (Ru-Ru v.s. Zr-Zr ) collisions that could provide the critical test of the CME in heavy ion collisions.

nucl-th↗

arXiv2015

Magnetic Field Effect on Charmonium Production in High Energy Nuclear Collisions

It is important to understand the strong external magnetic field generated at the very beginning of high energy nuclear collisions. We study the effect of the magnetic field on the charmonium yield and anisotropic distribution in Pb+Pb collisions at the LHC energy. The time dependent Schrödinger equation is employed to describe the motion of $c\bar{c}$ pairs. We compare our model prediction of non- collective anisotropic parameter $v_2$ of $J/ψ$s with CMS data at high transverse momentum. This is the first attempt to measure the magnetic field in high energy nuclear collisions.

hep-ph↗

arXiv2015

The "ripples" on relativistically expanding fluid

Recent studies have shown that fluctuations of various types play important roles in the evolution of the fireball created in relativistic heavy ion collisions and bear many phenomenological consequences for experimental observables. The bulk dynamics of the fireball is well described by relativistic hydrodynamic expansion and the fluctuations on top of such expanding background can be studied within the linearized hydrodynamic framework. In this work we present complete and analytic sound wave solutions on top of both Bjorken flow and Hubble flow backgrounds. We also briefly discuss the applications of these solutions in heavy ion collisions.

hep-th↗

arXiv2013

Conserved Charge Fluctuations and Susceptibilities in Strongly Interacting Matter

We study the conserved charge fluctuations, as quantified by the corresponding susceptibilities, in strongly interacting matter as motived by the quark-gluon plasma. Using the gauge-gravity correspondence approach, we study the patterns of conserved charge fluctuations in two types of holographic models for QCD, the D4/D8 and the D3/D7 models. We compute and compare the quark number susceptibilities in both models and find an interesting common feature of the two: at very strong coupling higher order susceptibilities are suppressed and the conserved charge fluctuations become purely Guassian. In light of the state-of-the-art lattice QCD results we also discuss what we can learn from these susceptibilities about the underlying degrees of freedom in the $1\sim 2T_c$ quark-gluon plasma and examine the viability of different ideas such as holography, quasi-particles, as well as bound states. From analyzes of second order susceptibilities we conclude that the bound states exist and are important in the $1\sim 2T_c$ region. We further construct and make predictions for several ratios of fourth-order susceptibilities that can sensitively reveal such bound states.

hep-ph↗

arXiv2013

Flavor Dependence of Meson Melting Temperature in Relativistic Potential Model

We study the melting temperature of heavy mesons in the hot medium of light quarks. By solving the covariant Schrödinger equations at finite temperature for mesons $D$, $ϕ$ and $J/ψ$, we obtained the temperature dependence of their masses, binding energies and averaged sizes and found the flavor dependence of the melting temperature: $T_D \simeq T_ϕ< T_{J/ψ}$. The sequential melting temperature can explain the difference in meson elliptic flow observed in heavy ion collisions.

nucl-th↗