arXiv subjects

Mei Huang

Publications and source records attributed to Mei Huang.

At least 55 records · Page 3Linked to original sources

arXiv2024

Exploring the chiral magnetic effect in isobar collisions through Chiral Anomaly Transport

We investigate the signal of the chiral magnetic effect (CME) in Au+Au collisions and isobar collisions of $_{44}^{96}\text{Ru}+\rm{} _{44}^{96}Ru$ and $_{40}^{96}\text{Zr}+\rm{}_{40}^{96}Zr$ in the newly developed chiral anomaly transport (CAT) module based on the state-of-the-art model a multiphase transport (AMPT). Our numerical simulation results for the ratio charge correlation $Δγ$ in Ru+Ru and Zr+Zr collisions are close to the latest experimental data. The simulation shows that the CME signal is larger in Ru+Ru collisions than that in Zr+Zr collisions, while the background is smaller, and the upper limit of the CME signal is $15\%$ in the isobar collisions.

hep-ph↗

arXiv2024

Dynamical induced quark spin polarization by magnetic field at the early stage of heavy-ion collisions

We present a comprehensive analysis of the dynamic process of quark spin polarization induced by magnetic fields at the pre-thermal stage in heavy-ion collisions by using the recently developed theoretical tool of chiral kinetic theory. Our findings demonstrate that the spin polarization of quarks is highly sensitive to the interactions between quarks. These interactions can delay the decay of early spin polarization vector while accelerating the decay of later spin polarization vector. Specifically, our simulations show the detailed process of how magnetic fields polarize quarks within the fireball and reveal that quark interactions lead to an acceleration effect on the average spin. Notably, the fireball of quark-gluon plasma (QGP) in its early stages exhibits an incomplete electromagnetic response effect, which differs from the response predicted by Lenz's law. This discrepancy arises from quantum corrections involving the interactions between quark spin and electromagnetic fields.

nucl-th↗

arXiv2024

The effect of charm quark on chiral phase transition in $N_f=2+1+1$ holographic QCD

We investigate the effect of charm quark on the chiral phase transition of light quarks at finite temperature based on the four-flavor soft-wall holographic QCD model. In the massless limit, we find that the thermal chiral phase transition is of the second order in the four-quark flavor system. In the case with the massive charm quark and the massless light and strange quarks, the order of the phase transition changes to the first order. This is due to the quark flavor symmetry breaking which is associated with the violation of the $U(1)$ axial symmetry. Once the light and strange quarks get massive, the explicit chiral symmetry breaking becomes eminent, then the crossover phase transition is realized at the physical quark masses. We also map the order of the phase transition on a phase diagram in the quark mass plane where the light- and strange-quark masses are degenerate but differ from the value of the charm quark mass. This phase diagram is an extension of the conventional Columbia plot to the four-quark flavor system. The critical exponents related to the chiral phase transition are also addressed.

hep-ph↗

arXiv2024

Effect of quark anomalous magnetic moment on neutral dense quark matter under magnetic field

We discuss the effect of the quark anomalous magnetic moment (AMM) on the neutral dense quark matter under magnetic fields based on the Nambu-Jona-Lasinio (NJL) model at finite baryon density. To address its correlation with the chiral symmetry, we consider a simplified situation: the model includes the two-quark flavors under constant magnetic fields, and incorporates the effective interaction of the quark AMM linked to the spontaneous chiral symmetry breaking. We then examine the equation of state (EoS) in cases with and without magnetization for anatomizing the thermodynamic quantities. Without the magnetization, a small magnetic field stiffens the EoS, but with increasing the magnetic field, the EoS tends to soften. The stiffness of the EoS is found to be influenced by the magnetic effect on the critical chemical potential of the chiral phase transition and the quark number density at this critical point. As a result, the mass and radius of the neutral dense quark matter increase with the small magnetic field but turn to decrease as the magnetic field further increases. By including the quark AMM, the critical chemical potential is decreased and the quark number density takes a smaller value. Thus, for the stronger magnetic fields, the quark AMM suppresses the softening effect of the magnetic field on the EoS, leading to increased mass and radius compared to when the quark AMM is absent. In contrast, for the small magnetic field, the contribution of the quark AMM to the EoS is marginal. When the magnetization is taken into account, the magnetic effect on the stiffness of the EoS is overshadowed by the contribution of the magnetization, and the significance of the quark AMM also becomes invisible in the mass-radius relation.

hep-ph↗

arXiv2024

Spin Alignment of Vector Mesons Induced by Local Spin Density Fluctuations

We propose a novel mechanism that the spin alignment of vector meson $ϕ$ and $K^{*0}$ in most central heavy ion collisions is induced by intrinsic QCD dynamics without external vortical/ magnetic fields. The local spin density fluctuation of quarks due to the axial-vector and tensor interactions between quarks can induce the spin alignments of vector meson. It is found that axial-vector interaction results in $ρ_{00}<1/3$ for the spin alignment of $ϕ$ meson, while tensor interaction results in $ρ_{00}>1/3$. We argue that the spin alignment of $K^{*0}$ due to the spin density fluctuation from flavor-mixing would be a signature or hint of instanton.

hep-ph↗

arXiv2024

Nanohertz gravitational waves and primordial quark nuggets from dense QCD matter in the early universe

The first-order QCD phase transition at high temperature features a large transition rate in the magnitude of $β/H \sim 10^4$ with induced stochastic gravitational waves typically lying in the LISA range. High baryon density in the early universe can be generated through Affleck-Dine baryogenesis. The baryon chemical potential enhances the potential barrier and significantly reduces the transition rate, which decreases from infinity at the critical end point (CEP) to zero at the critical nucleation point (CNP). Nanohertz gravitational waves can be produced in a narrow window of high baryon chemical potential with transition rate in the order of $β/H \sim 10^1$. When the phase transition rate reaches zero, the false vacuum of high baryon density quark matter is unlikely to decay and can persist over cosmological time scales. Therefore the primordial quark nuggets (PQN) can form and survive in the early universe as the seeds of compact stars, thereby dramatically accelerating the evolution of compact stars and the formation of galaxies, which may explain the high red-shift massive galaxies observed by the James Webb Space Telescope.

hep-ph↗

arXiv2024

Magnetic catalysis and diamagnetism from pion fluctuations

In the framework of Nambu--Jona-Lasinio model beyond mean field approximation, the effects of pion fluctuations on (inverse) magnetic catalysis and magnetic susceptibility are studied. The negative magnetic susceptibility at low temperature is observed when contributions from both neutral and charged pions are taken into account. In weak field approximation, it is observed that at finite temperature, the magnetic inhibition effect in the chiral limit, resulting from the difference between the transverse and longitudinal velocities of neutral pions, converts to weak magnetic catalysis when considering a non-zero current quark mass. Moreover, the magnetic catalysis is amplified by the charged pions.

hep-ph↗

arXiv2024

Pion Condensation and Pion Star from Holographic QCD

The properties of QCD matter at finite isospin densities are investigated employing holographic hard-wall and soft-wall AdS/QCD models. It is confirmed that at high enough isospin densities, charged pions start to condense and the pion superfluid phase appears in the system. It is shown that the chiral condensate and the pion condensate can be transformed to each other and form a `chiral circle' in the superfluid phase. We derived the Equation of State (EoS) for pionic matter, calculated the normalized trace anomaly $Δ$ and $(ε-3p)/m_π^4$, and analyzed the sound speed and adiabatic index. Additionally, we provided data on the mass-radius relation and tidal deformability of pion stars. The results indicate that the holographic models align well with lattice QCD concerning isospin density, axial-vector condensation, EoS, and trace anomaly, though discrepancies in sound speed and adiabatic index emerge at higher isospin chemical potentials. The holographic models closely match those from chiral perturbation theory ($χ$PT), suggesting that they can be considered as five-dimensional description of $χ$PT.

hep-ph↗

arXiv2024

The effect of vorticity on the dynamical magnetic fields in heavy-ion collisions

Magnetic fields in heavy-ion collisions are pivotal and subject to diverse factors. In this study, we quantitatively investigate the impact of fluid vorticity on the evolution of magnetic fields in the 20-50\% centrality class in Au+Au collisions, with collision energies of $\sqrt{s_{NN}}=(7.7, 14.5, 19.6, 27, 39, 62.4, 200)$ GeV. Our results indicate that fluid vorticity leads to a delay in the evolution of the magnetic field, in which this effect becomes more pronounced as the collision energy decreases. Additionally, we have calculated the mean magnetic field values on the freeze-out hypersurface for various collision energies. Our simulation results align with the values inferred from experimental data of $\barΛ-Λ$, within the error margins.

hep-ph↗

arXiv2024

Deconfinement and chiral restoration phase transition under rotation from holography in an anisotropic gravitational background

We investigate the effects of rotation on deconfinement and chiral phase transitions in the framework of dynamical holographic QCD model. Instead of transforming to the rotating system by Lorentz boost, we construct an anisotropic gravitational background by incorporating the rotating boundary current. We firstly investigate the pure gluon system under rotation to extract deconfinement phase transition from the Polyakov loop then add 2-flavor probe for chiral restoration phase transition from the chiral condensate. It is observed that at low chemical potentials, the deconfinement phase transition of pure gluon system is of first order and the chiral phase transition of 2-flavor system is of crossover. Both the critical temperatures of deconfinement and chiral phase transitions decrease/increase with imaginary/real angular velocity ($Ω_I/Ω$) as $T/T_c\sim 1- C_2 Ω_I^2$ and $T/T_c\sim 1+ C_2 Ω^2$, which is consistent with lattice QCD results. In the temperature-chemical potential $T-μ$ phase diagram, the critical end point (CEP) moves towards regions of higher temperature and chemical potential with real angular velocity.

hep-ph↗

arXiv2024

Bubble wall velocity and gravitational wave in the minimal left-right symmetric model

The bubble wall velocity in the first order phase transition plays an important role in determining both the amplitude and the pivot frequency of stochastic gravitational wave background. In the framework of the minimal left-right symmetric model, we study the wall velocity when the first order phase transition can occur. The wall velocity can be determined by matching the distribution functions in the free particle approximation and the local thermal equilibrium approximation. It is found that the wall velocity can be determined in the range $ 0.2 < v_w < 0.5 $ for the parameter space with the first order phase transition. It is also found that for the case when the wall velocity is close to the speed of sound, the peak amplitude of gravitational wave spectrum can be larger than that in the runaway case. Moreover, It is also found that there exists an approximate power law between the wall velocity and pressure difference between broken and symmetry phases, and the power index is equal to 0.41 or so.

gr-qc↗

arXiv2024

Net proton number cumulants from viscous hydro with equation of state including a critical end point

In the SMASH-CLVisc-hybrid framework, including SMASH for the initial conditions and the hadronic rescattering stage, and CLVisc for the quark gluon plasma (QGP) evolution, we investigate net baryon number fluctuations via considering the equation of state (EoS) with and without a critical end point (CEP) in the QCD phase transition. Specifically, two distinct QCD EoS are utilized: one with smooth crossover derived from NEOS and another with a critical end point sourced from the rPNJL model. Our results show that non-monotonic behavior of $κσ^2$ is not observed above the collision energy $7.7 {\rm GeV}$, nor are there explicit differences between the EoS characterized by crossover and that by CEP. This could be attributed to the significant deviation of the freeze-out line from the location of CEP. It is also found that the pure SMASH result of $κσ^2$ is positive and close to zero at 3 GeV, which is different from the negative value observed from STAR.

hep-ph↗

arXiv2024

Machine learning holographic black hole from lattice QCD equation of state

Based on lattice QCD results of equation of state (EOS) and baryon number susceptibility at zero baryon chemical potential, and supplemented by machine learning techniques, we construct the analytic form of the holographic black hole metric in the Einstein-Maxwell-Dilaton (EMD) framework for pure gluon, 2-flavor, and 2+1-flavor systems, respectively. The dilaton potentials solved from Einstein equations are in good agreement with the extended non-conformal DeWolfe-Gubser-Rosen (DGR) type dilaton potentials fixed by lattice QCD EOS, which indicates the robustness of the EMD framework. The predicted critical endpoint (CEP) in the 2+1-flavor system is located at $(T^c$=0.094GeV, $μ^c_B$=0.74GeV), which is close to the results from the realistic Polyakov-Nambu-Jona-Lasinio(PNJL) model, the functional renormalization group, and the holographic model with extended DeWolfe-Gubser-Rosen dilaton potential.

hep-ph↗

arXiv2024

Chiral phase transition and spin alignment of vector meson in the Polarized-Polyakov-loop Nambu-Jona-Lasinio model under rotation

By using the extrapolation method, a polarized Polykov-loop potential at finite real angular velocity is constructed from the lattice results at finite imaginary angular velocity. The chiral and deconfinement phase transitions under rotation have been simultaneously investigated in the Polarized-Polyakov-loop Nambu-Jona-Lasinio (PPNJL) model. It is observed that both critical temperatures of deconfinement and chiral phase transition increase with the angular velocity, which is in consistent with lattice results. The spin alignment of vector meson has the negative deviation of $ρ_{00} -1/3$ under rotation, and the deviation in the PPNJL model is much more significant than that in the NJL model and the quark coalescence model, which revealing the important role of rotating gluons on the quark polarization.

hep-ph↗

arXiv2023

The Splitting of Chiral and Deconfinement Phase Transitions induced by Rotation

The chiral and deconfinement phase transitions under rotation have been simultaneously investigated in the Polyakov-Nambu-Jona-Lasinio (PNJL) model. An interesting observation has been found that the chiral phase transition is catalyzed and the deconfinement phase transition is decelerated by rotation, therefore a chiral symmetric but confined phase is induced by rotation, which indicates that chiral dynamics and gluon dynamics can be split by rotation.

hep-ph↗

arXiv2023

Evolution of topological charge through chiral anomaly transport

Built upon the state-of-the-art model a multiphase transport (AMPT), we develop a new module of chiral anomaly transport (CAT), which can trace the evolution of the initial topological charge of gauge field created through sphaleron transition at finite temperature and external magnetic field in heavy ion collisions. The eventual experimental signals of chiral magnetic effect(CME) can be measured. The CAT explicitly shows the generation and evolution of the charge separation, and the signals of CME through the CAT are quantitatively in agreement with the experimental measurements in Au+Au collision at $\sqrt{s}=200 {\rm GeV}$, and the centrality dependence of the CME fraction follows that of the fireball temperature.

hep-ph↗

arXiv2023

$D_{(s)}-$ mesons semileptonic form factors in the 4-flavor holographic QCD

We investigate semileptonic form factors of $D_{(s)}$ meson from a modified soft-wall 4-flavor holographic model. The model successfully reproduces the masses and decay constants of various mesons, including $ρ$, $K^*$, $D^*$, $D_s^*$, $a_1$, $K_1$, $f_1$, $D_1$,$D_{s1}$, $π$, $K$, $η$, $D$, and $D_s$. Moreover, we study the semileptonic decay processes $D^{+} \to (π, K, η) l^{+} ν_{l}$ and $D_{s}^{+} \to ( K, η) l^{+} ν_{l}$, associated with the vector meson exchange, as well as $D_{(s)}^{+} \to K^{} l^{+} ν_{l}$, associated with the vector and axial vector meson exchange. The form factors $f_{+}(q^{2})$ for $D \toπ$ and $D_{(s)}\to K$ decays agree excellently with experimental and lattice data, outperforming other theoretical approaches. The $f_{+}(q^{2})$ form factor for $D^{+} \to η$ is compatible with experimental data, while a slight discrepancy is observed for $D_{s}^{+} \to η$ at large $q^{2}$. Additionally, we predict the vector form factors $V(q^{2})$ and $A_{1}(q^{2})$ for $D \to K^{}$ and $D_{s} \to K^{}$ decays, respectively. The results agree well with other approaches and lattice data at maximum recoil ($q^{2}=0$).

hep-ph↗

arXiv2023

The electromagnetic form factors in the $N_{f}=4$ holographic QCD

In this study, we employ a modified soft-wall holographic model with four flavors to investigate the meson spectra, decay constants, electromagnetic form factors, and charge radius of various mesons. We obtain the spectra for vector, axial vector, and pseudoscalar mesons. Decay constants are calculated and compared with experimental and lattice QCD data. The pion and kaon electromagnetic form factors are compared with the experimental data, and a good agreement is achieved for the kaon at low $Q^{2}$. For the charmed mesons, the electromagnetic form factors of the $D$ and $D_{s}$ and electric form factors of the $D^{*}$ and $D_{s}^{*}$ are well consistent with the lattice QCD data. Moreover, the electric, magnetic, and quadrupole form factors are predicted for the $ρ$, $K^{*}$, $a_1$, $K_1$, $D_1$, and $D_{s1}$ mesons. Furthermore, the charge radius of the vector, axial vector, and pseudoscalars, including the strange and charmed mesons, are computed.

hep-ph↗