arXiv subjects

Pengfei Zhuang

Publications and source records attributed to Pengfei Zhuang.

At least 145 records · Page 8Linked to original sources

arXiv2006

Effect of $U_A(1)$ Breaking on Chiral Phase Structure and Pion Superfluidity at Finite Isospin Chemical Potential

We investigate the isospin chemical potential effect in the frame of SU(2) Nambu-Jona-Lasinio model. When the isospin chemical potential is less than the vacuum pion mass, the phase structure with two chiral phase transition lines does not happen due to $U_A(1)$ breaking of QCD. When the isospin chemical potential is larger than the vacuum pion mass, the ground state of the system is a Bose-Einstein condensate of charged pions.

hep-ph↗

arXiv2006

Paramagnetic Meissner Effect and Finite Spin Susceptibility in an Asymmetric Superconductor

A general analysis of Meissner effect and spin susceptibility of a uniform superconductor in an asymmetric two-component fermion system is presented in nonrelativistic field theory approach. We found that, the pairing mechanism dominates the magnetization property of superconductivity, and the asymmetry enhances the paramagnetism of the system. At the turning point from BCS to breached pairing superconductivity, the Meissner mass squared and spin susceptibility are divergent at zero temperature. In the breached pairing state induced by chemical potential difference and mass difference between the two kinds of fermions, the system goes from paramagnetism to diamagnetism, when the mass ratio of the two species increases.

hep-ph↗

arXiv2006

Photoproduction of Pentaquark $Θ^+$ and Chiral Symmetry Restoration in Hot and Dense Medium

The photoproduction rate of pentaquark $Θ^+$ is calculated in a hot and dense medium. At high temperature and density, due to the restoration of chiral symmetry, photoproduction energy threshold is increased. Above the thresold the production cross section is strongly enhanced.

hep-ph↗

arXiv2005

Limit Temperatures for Meson and Diquark Resonances in a Strongly Interacting Quark Matter

We investigate mesons and diquarks as resonant states above chiral critical temperature $T_c$ in flavor SU(2) Nambu--Jona-Lasinio model. For each kind of resonance, we solve the pole equation for the resonant mass in the complex energy plane, and find an ultimate temperature where the pole starts to disappear. The phase diagram including these limit temperatures in $T-μ$ plane is obtained. The maximum limit temperature at $μ=0$ is approximately two times $T_c$.

hep-ph↗

arXiv2005

On the Ground State of Two Flavor Color Superconductor

The diquark condensate susceptibility in neutral color superconductor at moderate baryon density is calculated in the frame of two flavor Nambu-Jona-Lasinio model. When color chemical potential is introduced to keep charge neutrality, the diquark condensate susceptibility is negative in the directions without diquark condensate in color space, which may be regarded as a signal of the instability of the conventional ground state with only diquark condensate in the color 3 direction.

hep-ph↗

arXiv2005

Neutral Color Superconductivity and Pseudo-Goldstone Modes

Four of the five expected Goldstone modes, which will be eaten up by gauge fields, in neutral two-flavor color superconductor are actually pseudo-Goldstone modes, and their degenerated mass is exactly the magnitude of the color chemical potential, which is introduced to guarantee the color neutrality at moderate baryon density.

hep-ph↗

arXiv2005

Phase Structure of Color Superconductivity

We investigate color superconductivity and chiral symmetry restoration at finite temperature and baryon density in the frame of standard two flavor Nambu--Jona-Lasinio model. We derive the diquark mass in RPA, discuss its constraint on the coupling constant in the diquark channel, and find a strong competition between the two phase transitions when the coupling constant is large enough.

hep-ph↗

arXiv2005

Effect of Chiral Symmetry Restoration on Pentaquark $Θ^+$ Mass and Width at Finite Temperature and Density

We investigate the effect of chiral phase transition on the pentaquark $Θ^+$ mass and width at one-loop level of $NΘ^+K$ coupling at finite temperature and density. The behavior of the mass, especially the width in hadronic medium is dominated by the characteristics of chiral symmetry restoration at high temperature and high density. The mass and width shifts of positive-parity $Θ^+$ are much larger than that of negative-parity one, which may be helpful to determine the parity of $Θ^+$ in high energy nuclear collisions.

nucl-th↗

arXiv2005

Phase Structure of Nambu-Jona-Lasinio Model at Finite Isospin Density

In the frame of flavor SU(2) Nambu--Jona-Lasinio model with $U_A(1)$ breaking term we found that, the structure of two chiral phase transition lines does not exist at low isospin density in real world, and the critical isospin chemical potential for pion superfluidity is exactly the pion mass in the vacuum.

hep-ph↗

arXiv2004

J/psi transport in QGP and Pt distribution at SPS and RHIC

Combining the hydrodynamic equations for the QGP evolution and the transport equation for the primordially produced $J/ψ$ in the QGP, we investigate the $J/ψ$ transverse momentum distribution as well as its suppression in the $\sqrt{s}$=17.3A GeV Pb-Pb collisions at SPS and $\sqrt{s}$=200A GeV Au-Au collisions at RHIC. The two sets of equations are connected by the $J/ψ$ anomalous suppression induced by its inelastic scattering with gluons in the QGP. The calculated centrality dependence of $J/ψ$ suppression and average transverse momentum square agree well with the SPS data. From the comparison with the coalescence model where charm quark is fully thermalized, our calculated elliptical flow of the primordially produced $J/ψ$ is much smaller. This may be helpful to differentiate the $J/ψ$ production mechanisms in relativistic heavy ion collisions.

nucl-th↗

arXiv2003

Deconfinement Phase Transition in an Expanding Quark system in Relaxation Time Approximation

We investigated the effects of nonequilibrium and collision terms on the deconfinement phase transition of an expanding quark system in Friedberg-Lee model in relaxation time approximation. By calculating the effective quark potential, the critical temperature of the phase transition is dominated by the mean field, while the collisions among quarks and mesons change the time structure of the phase transition significantly.

hep-ph↗

arXiv2003

Breached Pairing Superfluidity at Finite Temperature and Density

A general analysis on Fermion pairing at finite temperature and density between different species with mismatched Fermi surfaces is presented. Very different from the temperature effect of BCS phase, the recently found breached pairing phase resulted from density difference of the two species lies in a region with calabash-like shape in the $T-μ$ plane, and the most probable temperature for the new phase's creation is finite but not zero.

cond-mat↗

arXiv2003

Low-momentum Pion Enhancement Induced by Chiral Symmetry Restoration

The thermal and nonthermal pion production by sigma decay and its relation with chiral symmetry restoration in a hot and dense matter are investigated. The nonthermal decay into pions of sigma mesons which are popularly produced in chiral symmetric phase leads to a low-momentum pion enhancement as a possible signature of chiral phase transition at finite temperature and density.

nucl-th↗

arXiv2003

Analytic Solution of Strongly Coupling Schroedinger Equations

A recently developed expansion method for analytically solving the ground states of strongly coupling Schrödinger equations by Friedberg, Lee and Zhao is extended to excited states and applied to the pedagogically important problems of power-law central forces. With the extended method, the Hydrogen atom problem is resolved and the low-lying states of Yukawa potential are approximately obtained.

quant-ph↗

arXiv2003

Exact Calculation of Ring Diagrams and the Off-shell Effect on the Equation of State

The partition function with ring diagrams at finite temperature is exactly caluclated by using contour integrals in the complex energy plane. It contains a pole part with temperature and momentum dependent mass and a phase shift part induced by off-shell effect in hot medium. The thermodynamic potentials for $ϕ^4$ and $ϕ^3$ interactions are calculated and compared with the quasi-particle (pole) approximation. It is found that the off-shell effect on the equation of state is remarkable.

hep-ph↗

arXiv2003

Quark Probability Distribution at Finite Temperature and Density

Quark deconfinement phase transition at finite temperature and density is investigated in the frame of quantum mechanics. By solving the Schrödinger equation for a heavy quark in a thermal mean field, we calculate the quark probability distribution as a function of temperature and density. The confined wave function in the vacuum expands outward rapidly when the temperature and density are high enough. The obtained phase transition line agrees qualitatively with the result of lattice QCD.

hep-ph↗

arXiv2003

Leakage Effect on J/psi Pt Distributions in Different Centrality Bins for Pb-Pb Collisions at E/A=160 GeV

A transport approach including a leakage effect for J/psi's in the transverse phase space is used to calculate the ratios between the J/psi transverse momentum distributions in several centrality bins for Pb-Pb collisions at E/A = 160 GeV. From the comparison with the CERN-SPS data, where the centrality is characterized by the transverse energy Et, the leakage effect is extremely important in the region of high transverse momentum and high transverse energy, and both the threshold and the comover models can describe the ratio well for all centrality bins except the most central one (Et < 100 GeV), for which the comover model calculation is considerably better than the threshold one.

nucl-th↗

arXiv2003

Time Structure of Anomalous J/psi and psi' suppression in nuclear collisions

The data for the mean squared transverse momentum P_t as function of transverse energy E_t of J/Psi and Psi' produced in Pb-Pb collisions at the CERN-SPS are analyzed and it is claimed that they contain information about the time structure of anomalous suppression. A transport equation which describes transverse motion of J/Psi and Psi' in the absorptive medium is proposed and solved for a QGP and a comover scenario of suppression. While the comover approach accounts for the data fairly well without adjusting any parameter, the fit to the data within the QGP scenario requires to assume anomalous suppression to become effective rather late, 3-4 fm/c after the nuclear overlap.

nucl-th↗