arXiv subjects

Mei Huang

Publications and source records attributed to Mei Huang.

At least 91 records · Page 5Linked to original sources

arXiv2021

Magnetic correction to the Anomalous Magnetic Moment of Electron

We investigate the leading order correction of anomalous magnetic moment (AMM) to the electron in weak magnetic field and find that the magnetic correction is negative and magnetic field dependent, indicating a magnetic catalysis effect for the electron gas. In the laboratory to measure the $g-2$, the magnitude of the magnetic field $B$ is several $\mathrm{T}$, correspondingly the magnetic correction to the AMM of electron/muon is around $10^{-34}$/$10^{-42}$, therefore the magnetic correction can be safely neglected in current measurement. However, when the magnitude of the magnetic field strength is comparable with the electron mass, the magnetic correction of electron's AMM will become considerable. This general magnetic correction to charged fermion's AMM can be extended to study QCD matter under strong magnetic field.

hep-ph↗

arXiv2021

Holographic QCD model for $N_f=4$

We establish a holographic QCD model for four flavors, where a light scalar field $X$ and a heavy scalar field $H$ are introduced, separately. The $H$ field is responsible for the breaking of $SU(N_f=4)$ to $SU(N_f=3)$. The ground state and its Regge excitation of meson spectra in the light flavor sector and heavy flavor sector as well as the ligh-heavy mesons are well in agreement with the Particle data group (PDG). Due to the additional introduction of the $H$ field in the model, different Regge slopes for light and heavy mesons can be achieved.

hep-ph↗

arXiv2021

Spectra of glueballs and oddballs and the equation of state from holographic QCD

We study the spectra of two-gluon glueballs and three-gluon oddballs and corresponding equation of state in $5$-dimensional deformed holographic QCD models in the graviton-dilaton system, where the metric, the dilaton field and dilaton potential are self-consistently solved from each other through the Einstein field equations and the equation of motion of the dilaton field. We compare the models by inputting the dilaton field, inputting the deformed metric and inputting the dilaton potential, and find that with only 2 parameters, the $5$-dimensional holographic QCD model predictions on glueballs/oddballs spectra in general are in good agreement with lattice results except two oddballs $0^{+-}$ and $2^{+-}$. From the results of glueballs/oddballs spectra at zero temperature and the equation of state at finite temperature, we observe that the model with quadratic dilaton field can simultaneously describe glueballs/oddballs spectra as well as equation of state of pure gluon system. The model with quadratic $A_{E}(z)$ can describe glueballs/oddballs spectra, but its corresponding equation of state behaves more like $N_{f}=2+1$ quark matter. These are consistent with dimension analysis at UV boundary.

hep-ph↗

arXiv2021

Gluodynamics and deconfinement phase transition under rotation from holography

We investigate rotating effect on deconfinement phase transition in an Einstein-Maxwell-Dilaton(EMD) model in bottom-up holographic QCD approach. By constructing a rotating black hole, which is supposed to be dual to rotating strongly coupled nuclear matter, we investigate the thermodynamic quantities, including entropy density, pressure, energy density, trace anomaly, sound speed and specific heat for both pure gluon system and two-flavor system under rotation. It is shown that those thermodynamic quantities would be enhanced by large angular velocity. Also, we extract the information of phase transition from those thermodynamic quantities, as well as the order parameter of deconfinement phase transition, i.e. the loop operators. It is shown that, in the $T - ω$ plane, for two-flavor case with small chemical potential, the phase transition is always crossover. The transition temperature decreases slowly with angular velocity and chemical potential. For pure gluon system with zero chemical potential, the phase transition is always first order, while at finite chemical potential a critical end point(CEP) will present in the $T - ω$ plane.

hep-ph↗

arXiv2021

Effect of the anomalous magnetic moment of quarks on magnetized QCD matter and meson spectra

We systematically investigate the effect of the anomalous magnetic moment(AMM) of quarks on the magnetized QCD matter, including the magnetic susceptibility, the inverse magnetic catalysis around the critical temperature and the neutral/charged pion and rho meson spectra under magnetic fields. The dynamical AMM of quarks, its coupling with magnetic field causes Zeeman splitting of the dispersion relation of quarks thus changes the magnetism properties and meson mass spectra under magnetic fields. It is found that including the AMM of quarks cannot fully understand lattice results of the magnetized matter: The AMM of quarks reduces the dynamical quark mass thus causes the inverse magnetic catalysis around $T_c$. The neutral pion mass is very sensitive to the AMM, it decreases with magnetic field quickly, and the charged pion mass shows a nonlinear behavior, i.e., firstly linearly increases with the magnetic field and then saturates at strong magnetic field. For rho meson, it is observed that AMM reduces the mass of neutral rho meson mass with different $s_z$, and reduces the mass of $s_z=+1,0$ component charged rho meson mass but enhances the $s_z=-1$ component charged rho meson mass. The magnetic susceptibility at low temperature can be either positive or negative with different AMM.

hep-ph↗

arXiv2020

Mass splitting of vector meson and spontaneous spin polarization under rotation

In the present paper, we study the effect of the rotation on the masses of scalar meson as well as vector meson in the framework of 2-flavor Nambu--Jona-Lasinio model. The existence of rotation causes a tedious quark propagator and corresponding polarization function. Applying the random phase approximation, the meson mass is calculated numerically. It is found that the behavior of scalar and pseudoscalar meson masses under the angular velocity $ω$ is similar to that at finite chemical potential, both rely on the behavior of constituent quark mass and reflect the property related to the chiral symmetry. However, masses of vector meson $ρ$ have more profound relation with rotation. After tedious calculation, it turns out that at low temperature and small chemical potenial, the mass for spin component $s_z=0,\pm 1$ of vector meson under rotation shows very simple mass splitting relation $m_ρ^{s_z}(ω)=m_ρ(ω=0)-ωs_z$, similar to the Zeeman splitting of charged meson under magnetic fields. Especially it is noticed that the mass of spin component $s_z=1$ vector meson $ρ$ decreases linearly with $ω$ and reaches zero at $ω_c=m_ρ(ω=0)$, this indicates the system will develop $s_z=1$ vector meson condensation and the system will be spontaneously spin polarized under rotation.

hep-ph↗

arXiv2020

Ellipticity of photon emission from strongly magnetized hot QCD plasma

By making use of an explicit representation for the imaginary part of the photon polarization tensor in terms of transitions between the Landau levels of light quarks, we study the angular dependence of direct photon emission from a strongly magnetized quark-gluon plasma. Because of the magnetic field, the leading order photon rate comes from the three processes of the zeroth order in the coupling constant $α_s$: (i) the quark splitting ($q\rightarrow q+γ$), (ii) the antiquark splitting ($\bar{q} \rightarrow \bar{q}+γ$), and (iii) the quark-antiquark annihilation ($q + \bar{q}\rightarrow γ$). In a wide range of moderately high temperatures, $T\gtrsim m_π$, and strong magnetic fields, $|eB|\gtrsim m_π^2$, the direct photon production is dominated by the two splitting processes. We show that the Landau-level quantization of quark states plays an important role in the energy and angular dependence of the photon emission. Among other things, it leads to a nontrivial momentum dependence of the photon ellipticity coefficient $v_2$, which takes negative values at small transverse momenta and positive values at large transverse momenta. The crossover between the two regimes occurs around $k_T\simeq \sqrt{|eB|}$. In application to heavy-ion collisions, this suggests that a large value of $v_2$ for the direct photons could be explained in part by the magnetic field in the quark-gluon plasma.

hep-ph↗

arXiv2020

Extraction of gluon distributions from structure functions at small x in holographic QCD

We investigate the nucleon and pion gluon distribution functions in the framework of holographic QCD, focusing on the small Bjorken x region. Based on an approximate relation, the gluon distributions are extracted from structure functions of the unpolarized deep inelastic scattering which can be calculated with a holographic QCD model, assuming the Pomeron exchange. All the adjustable parameters of the model are determined with the HERA data of the proton structure functions. We explicitly show that the extracted proton gluon distribution is consistent with results of the recent global QCD analysis. The structure functions of the pion can be computed without any additional parameter, which enables us to predict its gluon distribution also. We find that the resulting pion gluon density is smaller than the proton's, and agrees with the recent global QCD analysis result within the uncertainties.

hep-ph↗

arXiv2020

Extracting the magnitude of magnetic field at freeze-out in heavy-ion collisions

A strong magnetic field influences significantly the masses of the charged light mesons. For example, the mass of charged pion increases with the magnetic field increasing. We propose this mechanism as a possible way to extract the magnitude of magnetic field at freeze-out in heavy ion collisions and thus help constrain its lifetime which is currently a major open question to resolve. Specifically we show that the ratio between the yield of charged pions and that of charged rhos is very sensitive to the magnetic field value at freeze-out. By using a viscous-hydrodynamic framework (iEBE-VISHNU) to simulate heavy ion collisions and implementing magnetic-field-dependent meson masses, we compute their yields and predict the dependence of such ratio on the magnetic field. We suggest to use this ratio of charged rho yield over charged pion yield as an experimental observable to extract the possible magnetic field at freeze-out in heavy ion collisions.

hep-ph↗

arXiv2020

Total hadronic cross sections at high energies in holographic QCD

We present our analysis on high energy hadron-hadron scattering in the framework of the holographic QCD. Combining the Brower-Polchinski-Strassler-Tan Pomeron exchange kernel and gravitational form factors of the involved hadrons which are obtained by using the bottom-up AdS/QCD models in the five-dimensional AdS space, we calculate the total cross sections at high energies. We show that our calculations for the nucleon-nucleon scattering agree with the experimental data including the recent ones taken by the TOTEM collaboration at the LHC. The present framework is applicable to any high energy process, in which the strong interaction can be approximated by the Pomeron exchange. We present the results for the pion-nucleon and pion-pion scattering as examples, which can be obtained without any additional parameter because all the adjustable parameters are fixed via the analysis on the nucleon-nucleon scattering. The resulting total cross section ratios are $σ_{tot}^{πN} / σ_{tot}^{N N} = 0.63$ and $σ_{tot}^{ππ} / σ_{tot}^{N N} = 0.45$, respectively.

hep-ph↗

arXiv2020

Quarkyonic phase from quenched dynamical holographic QCD model

Chiral and deconfinement phase transitions at finite temperature $T$ and quark number chemical potential $μ$ are simultaneously studied in the quenched dynamical holographic QCD model within the Einstein-Dilaton-Maxwell framework. By calculating the corresponding order parameters, i.e., the chiral condensate and Polyakov loop, it is shown that the transition lines of these two phase transitions are separated in the $T-μ$ plane. The deconfinement phase transition is shown to be always of crossover type and the transition line depends weakly on the baryon number density. Differently, the chiral transition is of crossover at small baryon number density and it turns to be of first order at sufficient large baryon number density. A critical endpoint (CEP), at which the transition becomes second order type, appears in the chiral transition line. This is the first time to realize the CEP of chiral phase transition in the $(T, μ)$ plane using the holographic EMD(Einstein-Maxwell-Dilaton) model for two flavour case. It is observed that between these two phase transition lines, there is a region with chiral symmetry restored and color degrees still confined, which could be considered as the quarkyonic phase. Qualitatively, this behavior is in consistent with the result in the Polyakov-loop improved Nambu-Jona-Lasinio (PNJL) model.

hep-ph↗

arXiv2020

The entanglement properties of holographic QCD model with a critical end point

We investigate different entanglement properties of a holographic QCD (hQCD) model with a critical end point at finite baryon density. Firstly we consider the holographic entanglement entropy (HEE) of this hQCD model in a spherical shaped region and a strip shaped region, respectively, and find that the HEE of this hQCD model in both regions can reflect QCD phase transition. What is more is that although the area formulas and minimal area equations of the two regions are quite different, the HEE have very similar behavior on the QCD phase diagram. So we argue that the behavior of HEE on the QCD phase diagram is independent of the shape of subregions. However, as we know that HEE is not a good quantity to characterize the entanglement between different subregions of a thermal system. So we then study the mutual information (MI), conditional mutual information (CMI) and the entanglement of purification (Ep) in different strip shaped regions. We find that the three entanglement quantities have very similar behavior: their values do not change so much in the hadronic matter phase and then rise up quickly with the increase of $T$ and $\m$ in the QGP phase. Near the phase boundary, these three entanglement quantities change smoothly in the crossover region, continuously but not smoothly at CEP and show discontinuity behavior in the first phase transition region. And all of them can be used to distinguish different phases of strongly coupled matter.

hep-th↗

arXiv2019

Holographic Technicolor Model and Dark Matter

We investigate the strongly coupled minimal walking technicolor model (MWT) in the framework of a bottom-up holographic model, where the global $SU(4)$ symmetry breaks to $SO(4)$ subgroup. In the holographic model, we found that 125GeV composite Higgs particles and small Peskin-Takeuchi $S$ parameter can be achieved simultaneously. In addition, the model predicts a large number of particles at the TeV scale, including dark matter candidate Technicolor Interacting Massive Particles (TIMPs). If we consider the dark matter nuclear spin-independent cross-section in the range of $10^{-45}\sim 10 ^ {-48} $cm$^2$, which can be detected by future experiments, the mass range of TIMPs predicted by the holographic technicolor model is 2 $\sim$ 4 TeV.

hep-ph↗

arXiv2019

Quantized first-order phase transition and two sets of critical end point in droplet quark matter

The finite-size effect on the chiral phase transition is investigated in the Nambu--Jona-Lasinio model. To take into account finite-size effects, momentum integrals are replaced by momentum summations. The ground state of quark matter at finite size is favored when applying the periodic spatial boundary condition for quarks. The zero-momentum contribution is taken into account in the periodic boundary condition, and its contribution becomes important when the system size is comparable with the pion wavelength. When the zero-mode contribution becomes dominant, the conventional first-order chiral phase transition at high baryon chemical potential splits into two first-order phase transitions in small system of quark matter, and two sets of critical end point show up in the temperature and chemical potential plane.

hep-ph↗

arXiv2019

Effects of transmutation elements in tungsten

Tungsten (W) is widely considered as the most promising plasma facing material (PFM), which will be used in nuclear fusion devices. Due to the transmutation reaction caused by the fusion neutron irradiation, transmutation elements (such as Re, Os, and Ta) are generated in the W-based PFM during the operation of nuclear fusion devices. In this paper, transmutation elements effects on mechanical properties of the W and the behavior of hydrogen/helium (H/He) atom in the W were investigated by using the first-principles calculation method. The results show that the ductility of the W is enhanced by transmutation elements if dislocation and other defects were ignored, while mechanical properties of the W incompletely depend on transmutation elements content. Compared with the pure W, the formation energy of the H/He in the W is reduced by transmutation elements, but the most favorable sites of the H/He in the W is not changed. Except for a repulsion between Ta and He in the W, the H/He in the W is attracted by transmutation elements. In addition, transmutation elements can change the best diffusion path of the H/He in the W and increase the diffusion rate of the H/He in W. This study provides a theoretical basis for the Tungsten (W) application, and further study on the effects of transmutation elements in the W will be needed.

cond-mat.mtrl-sci↗

arXiv2019

The kurtosis of net baryon number fluctuations from a realistic Polyakov--Nambu--Jona-Lasinio model along the experimental freeze-out line

Firstly we qualitatively analyze the formation of the dip and peak structures of the kurtosis $κσ^2$ of net baryon number fluctuation along imagined freeze-out lines and discuss the signature of the existence of the QCD critical end point (CEP) in the Nambu--Jona-Lasinio (NJL) model, Polyakov-NJL (PNJL) model as well as $μ$-dependent PNJL($μ$ PNJL) model with different parameter sets, and then we apply a realistic PNJL model with parameters fixed by lattice data at zero chemical potential, and quantitatively investigate its $κσ^2$ along the real freeze-out line extracted from experiments. The important contribution from gluodynamics to the baryon number fluctuations is discussed. The peak structure of $κσ^2$ along the freeze-out line is solely determined by the existence of the CEP mountain and can be used as a clean signature for the existence of CEP. The formation of the dip structure is sensitive to the relation between the freeze-out line and the phase boundary, and the freeze-out line starts from the back-ridge of the phase boundary is required. To our surprise, the kurtosis $κσ^2$ produced from the realistic PNJL model along the experimental freeze-out line agrees with BES-I data well, which indicates that equilibrium result can explain the experimental data. It is worth to point out that the extracted freeze-out temperatures from beam energy scan measurement are indeed higher than the critical temperatures at small chemical potentials, which supports our qualitative analysis.

hep-ph↗

arXiv2019

Quark matter under rotation in the NJL model with vector interaction

We study the chiral phase transition of quark matter under rotation in two-flavor Nambu--Jona-Lasinio (NJL) model. It is found that, in the rotating frame, the angular velocity plays the similar role as the baryon chemical potential and suppresses the chiral condensate, thus the chiral phase transition shows a critical end point not only in the temperature-chemical potential $T-μ$ plane, but also in the temperature-angular momentum $T-ω$ plane. One interesting observation is that in the $T-μ$ plane, the presence of the angular momentum only shifts down the critical temperature $T^E$ of the CEP and does not shift the critical chemical potential $μ^E$, and in the $T-ω$ plane, the increase of the chemical potential only shift down the critical temperature $T^E$ and does not change the critical angular momentum $ω^E$. The phase structure in the $T-μ$ plane is sensitive to the coupling strength in the vector channel, while the phase structure in $T-ω$ plane is not. It is also observed that the rotating angular velocity suppresses the kurtosis of the baryon number fluctuations, while it enhances the pressure density, energy density, the specific heat and the sound velocity.

hep-ph↗

arXiv2018

Criticality of QCD in a holographic QCD model with critical end point

Thermodynamics of strongly interacting matter near critical end point are investigated in a holographic QCD model, which could describe the QCD phase diagram in $T-μ$ plane qualitatively. Critical exponents along different axis ($α,β,γ,δ$) are extracted numerically. It is given that $α\approx 0, β\approx 0.54, γ\approx 1.04, δ\approx 3.0$, the same as 3D Ising mean-field approximation and previous holographic QCD model calculations. We also discuss the possibilities to go beyond mean field approximation by including the full back-reaction of chiral dynamics in the holographic framework.

hep-ph↗