arXiv subjects

P. Z. Ning

Publications and source records attributed to P. Z. Ning.

15 recordsLinked to original sources

arXiv2008

The $ΣΣ$ interactions in finite-density QCD sum rules

The properties of $Σ$-hyperons in pure $Σ$ matter are studied with the finite-density quantum chromo-dynamics sum rule (QCDSR) approach. The $ΣΣ$ nuclear potential $U_Σ$ is most likely strongly attractive, it could be about -50 MeV or even more attractive at normal nuclear density. If this prediction is the case, the interactions between $Σ$-hyperons should play crucial roles in the strange nuclear matter, when there are multi-$Σ$ hyperons. The bound state of double-$Σ$ maybe exist.

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arXiv2008

Eta-mesic nuclei in relativistic mean-field theory

With the eta-nucleon (eta N) interaction Lagrangian deduced from chiral perturbation theory, we study the possible eta-mesic nuclei in the framework of relativistic mean-field theory. The eta single-particle energies are sensitive to the eta N scattering length, and increase monotonically with the nucleon number A. If the scattering length is in the range of a^{eta N}=0.75-1.05 fm and the imaginary potential V_{0}-15 MeV, some discrete states of C, O and Ne eta bound states should be identified in experiments. However, when the scattering length a^{eta N}< 0.5 fm, or the imaginary potential V_{0} > 30 MeV, no discrete eta meson bound states could be observed in experiments.

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arXiv2007

$Λ$$Λ$ interactions in finite-density QCD sum rules

The properties of $Λ$-hyperons in pure $Λ$ matter are studied with the finite-density QCD sum rule approach. The first order quark and gluon condensates in $Λ$ nuclear matter are deduced from the chiral perturbation theory. The sum rule predictions are sensitive to the four-quark condensates, $<\bar{q}q>^2_ρ$ and $<\bar{q}q>_ρ<\bar{s}s>_ρ$, and the $πN$ sigma term. When $<\bar{q}q>^2_ρ$ is nearly independent of density and $<\bar{q}q>_ρ<\bar{s}s>_ρ$ depends strongly on density, we can obtain weakly attractive $Λ$$Λ$ potentials (about several MeV) in low $Λ$ density region, which agree with the information from the latest double $Λ$ hyper-nucleus experiments. The nearly no density dependence of $<\bar{q}q>^2_ρ$ and strong density dependence of $<\bar{q}q>_ρ<\bar{s}s>_ρ$ can be explained naturally if the properties of $<\bar{q}q>^2_ρ$ and $<\bar{q}q>_ρ<\bar{s}s>_ρ$ are assumed to be similar to those of $ππ$ and $\bar{K} K$ in nuclear medium, respectively.

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arXiv2007

On the momentum-dependence of $K^{-}$-nuclear potentials

The momentum dependent $K^{-}$-nucleus optical potentials are obtained based on the relativistic mean-field theory. By considering the quarks coordinates of $K^-$ meson, we introduced a momentum-dependent "form factor" to modify the coupling vertexes. The parameters in the form factors are determined by fitting the experimental $K^{-}$-nucleus scattering data. It is found that the real part of the optical potentials decrease with increasing $K^-$ momenta, however the imaginary potentials increase at first with increasing momenta up to $P_k=450\sim 550$ MeV and then decrease. By comparing the calculated $K^-$ mean free paths with those from $K^-n$/$K^-p$ scattering data, we suggested that the real potential depth is $V_0\sim 80$ MeV, and the imaginary potential parameter is $W_0\sim 65$ MeV.

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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 $2.1ρ_{0}$.

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arXiv2005

The hyperon mean free paths in the relativistic mean field

The $Λ$- and $Ξ^-$-hyperon mean free paths in nuclei are firstly calculated in the relativistic mean field (RMF) theory. The real parts of the optical potential are derived from the RMF approach, while the imaginary parts are obtained from those of nucleons with the relations: $U^{\mathrm{IY}}_{\mathrm{S}} = α_{σ\mathrm{Y}}\cdot U_{\mathrm{S}}^{\mathrm{IN}}$ and $U^{\mathrm{IY}}_{\mathrm{V}} = α_{ω\mathrm{Y}}\cdot U_{\mathrm{V}}^{\mathrm{IN}}$ . With the assumption, the depth of the imaginary potential for $Ξ^-$ is $W_Ξ\simeq-$ 3.5 MeV, and for $Λ$ is $W_Λ\simeq-$ 7 MeV at low incident energy. We find that, the hyperon mean free path decreases with the increase of the hyperon incident energies, from 200 MeV to 800 MeV; and in the interior of the nuclei, the mean free path is about $2\sim 3$ fm for $Λ$, and about $4\sim 8$ fm for $Ξ^-$, depending on the hyperon incident energy.

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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.

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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

Some Calculations for Cold Fusion Superheavy Elements

The Q value and optimal exciting energy of the hypothetical superheavy nuclei in cold fusion reaction are calculated with relativistic mean field model and semiemperical shell model mass equation(SSME) and the validity of the two models is tested. The fusion barriers are also calculated with two different models and reasonable results are obtained. The calculations can give useful references for the experiments in the superheavy nuclei synthesized in cold fusion reactions.

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arXiv2004

$Θ^{+}$ hypernuclei in relativistic mean field model

We have investigated the properties of $Θ^{+}$ in nuclei within the framework of relativistic mean field. The coupling constants are educed with quark meson coupling model. There is strong attractive interaction for $Θ^{+}$-nucleus and $Θ^{+}$ can be bind in nuclei. The depth of optical potential for $Θ^{+}$ in nuclear matter is estimated.

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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

Quark mean field model with density dependent couplings for finite nuclei

The quark mean field model, which describes the nucleon using the constituent quark model, is applied to investigate the properties of finite nuclei. The couplings of the scalar and vector mesons with quarks are made density dependent through direct coupling to the scalar field so as to reproduce the relativistic Brueckner-Hartree-Fock results of nuclear matter. The present model provides satisfactory results on the properties of spherical nuclei, and predicts an increasing size of the nucleon as well as a reduction of the nucleon mass in the nuclear environment

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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

Charge and critical density of strange quark matter

The electric charge of strange quark matter is of vital importance to experiments. A recent investigation shows that strangelets are most likely highly negatively charged, rather than slightly positively charged as previously believed. Our present study indicates that negative charges can indeed lower the critical density, and thus be favorable to the experimental searches in heavy ion collisions. However, too much negative charges can make it impossible to maintain flavor equilibrium.

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arXiv1997

Mass formulae and strange quark matter

We have derived the popularly used parametrization formulae for quark masses at low densities and modified them at high densities within the mass-density-dependent model. The results are applied to investigate the lowest density for the possible existence of strange quark matter at zero temperature.

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