arXiv subjects

G. X. Peng

Publications and source records attributed to G. X. Peng.

At least 37 records · Page 2Linked to original sources

arXiv2014

Thermodynamic consistency, quark mass scaling, and properties of strange matter

The previous thermodynamic treatment for models with density and/or temperature dependent quark masses is shown to be inconsistent with the requirement of fundamental thermodynamics. We therefore study a fully self-consistent one according to the fundamental differential equation of thermodynamics. After obtaining a new quark mass scaling with the inclusion of both confinement and leading-order perturbative interactions, we investigate properties of strange quark matter in the fully consistent thermodynamic treatment. It is found that the equation of state become stiffer, and accordingly, the maximum mass of strange stars is as large as about 2 times the solar mass, if strange quark matter is absolutely or metastable.

hep-ph↗

arXiv2014

Magnetized strange quark matter in a mass-density-dependent model

We investigate the properties of strange quark matter in a strong magnetic field with quark confinement by the density dependence of quark mass considering the total baryon number conservation, charge neutrality and chemical equilibrium. The strength of the magnetic field considered in this article is $10^{16} \sim 10^{20}$ G. It is found that an additional term should appear in the pressure expression to maintain thermodynamic consistency. At fixed density, the energy density of magnetized strange quark matter varies with the magnetic field strength. The exists a minimum with increasing the field strength, depending on the density. It is about $6\times10^{19}$ Gauss at two times the normal nuclear saturation density.

nucl-th↗

arXiv2008

Deconfinement phase transition in hybrid neutron stars from the Brueckner theory with three-body forces and a quark model with chiral mass scaling

We study the properties of strange quark matter in equilibrium with normal nuclear matter. Instead of using the conventional bag model in quark sector, we achieve the confinement by a density-dependent quark mass derived from in-medium chiral condensates. In nuclear matter, we adopt the equation of state from the Brueckner-Bethe-Goldstone approach with three-body forces. It is found that the mixed phase can occur, for a reasonable confinement parameter, near the normal nuclear saturation density, and goes over into pure quark matter at about 5 times the saturation. The onset of mixed and quark phases is compatible with the observed class of low-mass neutron stars, but it hinders the occurrence of kaon condensation.

astro-ph↗

arXiv2007

Charge, strangeness and radius of strangelets

We investigate, at both zero and finite temperature, the properties of strangelets versus the electric charge Z and strangeness S. The strangelet radius is not a monotonic function of either charge or strangeness, and a minimum is reached in the (Z, S) plane. However, the thermodynamically stable strangelets do not correspond to the radius minimum. The minimum radius always appears at positive strangeness, while the stable radius may appear at negative strangeness for very small baryon numbers. For large baryon numbers, the stable radius is proportional to the cubic root of baryon numbers, but inversely proportional to the square root of the confinement parameter in the present model. If bulk strange quark matter is absolutely stable, the reduced size of strangelets is about 1 fm, which may be relevant for the analysis of the strangelet production and detection.

hep-ph↗

arXiv2006

Color-flavor locked strangelets in a quark mass density-dependent model

The color-flavor locked (CFL) phase of strangelets is investigated in a quark mass density-dependent model. Parameters are determined by stability arguments. It is concluded that three solutions to the system equations can be found, corresponding, respectively, to positively charged, negatively charged, and nearly neutral CFL strangelets. The charge to baryon number of the positively charged strangelets is smaller than the previous result, while the charge of the negatively charged strangelets is nearly proportional in magnitude to the cubic-root of the baryon number. However, the positively charged strangelets are more stable compared to the other two solutions.

hep-ph↗

arXiv2006

The properties of kaonic nuclei in relativistic mean-field theory

The static properties of some possible light and moderate kaonic nuclei, from C to Ti, are studied in the relativistic mean-field theory. The 1s and 1p state binding energies of $K^-$ are in the range of $73\sim 96$ MeV and $22\sim 63$ MeV, respectively. The binding energies of 1p states increase monotonically with the nucleon number A. The upper limit of the widths are about $42\pm 14$ MeV for the 1s states, and about $71\pm 10$ MeV for the 1p states. The lower limit of the widths are about $12\pm 4$ MeV for the 1s states, and $21\pm 3$ MeV for the 1p states. If $V_{0}\leq 30$ MeV, the discrete $K^-$ bound states should be identified in experiment. The shrinkage effect is found in the possible kaonic nuclei. The interior nuclear density increases obviously, the densest center density is about $2.1ρ_{0}$.

nucl-th↗

arXiv2006

Renormalization group dependence of the QCD coupling

The general relation between the standard expansion coefficients and the beta function for the QCD coupling is exactly derived in a mathematically strict way. It is accordingly found that an infinite number of logarithmic terms are lost in the standard expansion with a finite order, and these lost terms can be given in a closed form. Numerical calculations, by a new matching-invariant coupling with the corresponding beta function to four-loop level, show that the new expansion converges much faster.

hep-th↗

arXiv2005

New solutions for the color-flavor locked strangelets

Recent publications rule out the negatively charged beta equilibrium strangelets in ordinary phase, and the color-flavor locked (CFL) strangelets are reported to be also positively charged. This letter presents new solutions to the system equations where CFL strangelets are slightly negatively charged. If the ratio of the square-root bag constant to the gap parameter is smaller than 170 MeV, the CFL strangelets are more stable than iron and the normal unpaired strangelets. For the same parameters, however, the positively charged CFL strangelets are more stable.

hep-ph↗

arXiv2005

$η$-meson in nuclear matter

The $η$-nucleon ($η$N) interactions are deduced from the heavy baryon chiral perturbation theory up to the next-to-leading-order terms. Combining the relativistic mean-field theory for nucleon system, we have studied the in-medium properties of $η$-meson. We find that all the elastic scattering $η$N interactions come from the next-to-leading-order terms. The $η$N sigma term is found to be about 280$\pm$130 MeV. The off-shell terms are also important to the in-medium properties of $η$-meson. On application of the latest determination of the $η$N scattering length, the ratio of $η$-meson effective mass to its vacuum value is near $0.84\pm0.015$, while the optical potential is about $-(83\pm5)$ MeV, at the normal nuclear density.

nucl-th↗

arXiv2005

In-medium Properties of $Θ^{+}$ as a K$π$N structure in Relativistic Mean Field Theory

The properties of nuclear matter are discussed with the relativistic mean-field theory (RMF).Then, we use two models in studying the in-medium properties of $Θ^+$: one is the point-like $Θ^*$ in the usual RMF and the other is a K$π$N structure for the pentaquark. It is found that the in-medium properties of $Θ^+$ are dramatically modified by its internal structure. The effective mass of $Θ^+$ in medium is, at normal nuclear density, about 1030 MeV in the point-like model, while it is about 1120 MeV in the model of K$π$N pentaquark. The nuclear potential depth of $Θ^+$ in the K$π$N model is approximately -37.5 MeV, much shallower than -90 MeV in the usual point-like RMF model.

nucl-th↗

arXiv2005

Thermodynamics with density and temperature dependent particle masses and properties of bulk strange quark matter and strangelets

Thermodynamic formulas for investigating systems with density and/or temperature dependent particle masses are generally derived from the fundamental derivation equality of thermodynamics. Various problems in the previous treatments are discussed and modified. Properties of strange quark matter in bulk and strangelets at both zero and finite temperature are then calculated based on the new thermodynamic formulas with a new quark mass scaling, which indicates that low mass strangelets near beta equilibrium are multi-quark states with an anti-strange quark, such as the pentaquark (u^2d^2\bar{s}) for baryon nmber 1 and the octaquark (u^4d^3\bar{s}) for dibaryon etc.

hep-ph↗

arXiv2004

Chiral condensates and size of the sigma term

The in-medium chiral condensate is studied with a new approach which has the advantage of no need for extra assumptions on the current mass derivatives of model parameters. It is shown that the pion-nucleon sigma term is 9/2 times the average current mass of light quarks, if quark confinement is linear. Considering both perturbative and non-perturbative interactions, the chiral condensate decreases monotonously with increasing densities, approaching to zero at about 4 fm^{-3}.

nucl-th↗

arXiv2003

A new treatment of the in-medium chiral condensates

A new formalism to calculate the in-medium chiral condensate is presented. At lower densities, this approach leads to a linear expression. If we demand a compatibility with the famous model-independent result, then the pion-nucleon sigma term should be six times the average current mass of light quarks. QCD-like interactions may slow the decreasing behavior of the condensate with increasing densities, compared with the linear extrapolation, if densities are lower than twice the nuclear saturation density. At higher densities, the condensate vanishes inevitably.

hep-ph↗

arXiv2003

Chiral Condensates in Quark and nuclear Matter

We present a novel treatment for calculating the in-medium quark condensates. The advantage of this approach is that one does not need to make further assumptions on the derivatives of model parameters with respect to the quark current mass. The normally accepted model-independent result in nuclear matter is naturally reproduced. The change of the quark condensate induced by interactions depends on the incompressibility of nuclear matter. When it is greater than 260 MeV, the density at which the condensate vanishes is higher than that from the linear extrapolation. For the chiral condensate in quark matter, a similar model-independent linear behavior is found at lower densities, which means that the decreasing speed of the condensate in quark matter is merely half of that in nuclear matter if the pion-nucleon sigma commutator is six times the average current mass of u and d quarks. The modification due to QCD-like interactions is found to slow the decreasing speed of the condensate, compared with the linear extrapolation.

hep-ph↗

arXiv2001

Study of N*(1440) from J/Psi Decays

For $J/Ψ\to\bar pp π^0$ and $\bar ppπ^+π^-$, the $π^0p$ and $pπ^+π^-$ systems are limited to be pure isospin 1/2 due to isospin conservation. This is a big advantage in studying $N^*$ resonances from $J/Ψ$ decays, compared with $πN$ and $γN$ experiments. The process $J/Ψ\to\bar pN^*$ or $p\bar N^*$ provides a new way to probe the internal structure of the $N^*$ resonances. Here we report a quark model calculation for $J/Ψ\to\bar pp$, $pN^*(1440)$ and $\bar N^*N^*$. The implication for the internal structure of $N^*(1440)$ is discussed.

hep-ph↗

arXiv2001

Study of N* Production from J/Psi--> p pbar eta

Data are presented on the reaction J/psi--> p pbar eta using 7.8 million J/psi triggers collected by the BEjing Spectrometer (BES). A partial wave analysis is performed. A clear enhancement near the p eta(pbar eta) threshold is observed. It is fitted with a JP=1/2- resonance with mass $M= 1530\pm 10$ MeV and width $Γ= 95\pm 25$ MeV. In addition, there is a peak around 1650 MeV with JP=1/2- preferred also, fitted with $M =1647\pm 20$ MeV and $Γ= 145^{+80}_{-45}$ MeV. These two N* resonances are believed to be the two well established states, S11(1535) and S11(1650), respectively. It is the first partial wave study of the production of these resonances from J/psi decays.

hep-ex↗

arXiv2000

Thermodynamics, strange quark matter, and strange stars

Because of the mass density-dependence, an extra term should be added to the expression of pressure. However, it should not appear in that of energy according to both the general ensemble theory and basic thermodynamic principle. We give a detail derivation of the thermodynamics with density-dependent particle masses. With our recently determined quark mass scaling, we study strange quark matter in this new thermodynamic treatment, which still indicates a possible absolute stability as previously found. However, the density behavior of the sound velocity is opposite to the previous finding, but consistent with one of our recent publication. We have also studied the structure of strange stars using the obtained equation of state.

hep-ph↗

arXiv1999

Mass formulas and thermodynamic treatment in the mass-density-dependent model of strange quark matter

The previous treatments for strange quark matter in the quark mass-density-dependent model have unreasonable vacuum limits. We provide a method to obtain the quark mass parametrizations and give a self-consistent thermodynamic treatment which includes the MIT bag model as an extreme. In this treatment, strange quark matter in bulk still has the possibility of absolute stability. However, the lower density behavior of the sound velocity is opposite to previous findings.

hep-ph↗