We explore the equation of state for nuclear matter in the quark-meson coupling model, including full Fock terms. The comparison with phenomenological constraints can be used to restrict the few additional parameters appearing in the Fock terms which are not present at Hartree level. Because the model is based upon the in-medium modification of the quark structure of the bound hadrons, it can be applied without additional parameters to include hyperons and to calculate the equation of state of dense matter in beta-equilibrium. This leads naturally to a study of the properties of neutron stars, including their maximum mass, their radii and density profiles.
We consider heavy mesons with charm and bottom in nuclear medium. We construct the effective Lagrangian with axial-vector coupling including 1/M-corrections for the heavy meson mass $M$ by following the velocity-rearrangement invariance. As an application, we consider heavy mesons, $\bar{\mathrm{D}}$ and $\bar{\mathrm{D}}^{\ast}$ mesons for charm and $\mathrm{B}$ and $\mathrm{B}^{\ast}$ mesons for bottom, bound in nuclear matter, and we discuss their in-medium masses modified by the interaction with nucleons via pion exchanges including the 1/M-corrections. The mass modifications are affected …
It is shown that recently proposed RMF model with $σ$ and $δ$ meson interaction agrees with the observational data and presents an interesting structure with phase transition in the outer part of neutron star core.
In the framework of relativistic mean field theory, the relativistic neutrino emissivity of the nucleonic and hyperonic direct Urca processes in the degenerate baryon matter of neutron stars are studied. We investigate particularly the influence of the isovector scalar interaction which is considered by exchanging $δ$ meson on the nucleonic and hyperonic direct Urca processes. The results indicate that $δ$ mesons lead to obvious enhancement of the total neutrino emissivity, which must result in more rapid cooling rate of neutron star matter.
The possibility of meson condensation in stars and in heavy-ion collisions has been discussed in the past. Here, we study whether rho meson condensation ($ρ^{-}$) can occur in very dense matter and determine the effect of strong magnetic fields on this condensation. We find that rho meson condensates can appear in the core of the neutron star assuming a rho mass which is reduced due to in-medium effects. We find that the magnetic field has a non-negligible effect in triggering condensation.
We present a comprehensive study of mass modifications of scalar, pseudo-scalar, vector, and axial-vector mesons in nuclear matter using the three-flavor extended Linear Sigma Model (eLSM) and the two-flavor Parity Doublet Model (PDM). The meson masses in nuclear matter are determined by calculating the one-loop nucleon corrections to the meson mean fields. As a result, we find all spin-$0$ meson masses except those of the pion, kaon, and the lightest scalar-isoscalar mesons decrease at finite baryon density. For spin-$1$ mesons, masses of all axial-vector mesons decrease in medium, and the de…
We investigate the $s$-wave three-body system of two neutrons and one flavored meson with total spin-isospin $J=0,I=3/2$. The meson-neutron scattering length can become infinitely large in an unphysical region of the quark mass when extrapolated from strangeness to charm in the so-called zero coupling limit. Using a low-energy cluster effective field theory, we demonstrate that the Efimov effect is manifest in the three-body system when the meson-neutron scattering length is extrapolated to the unitary limit of the two-body interaction. We thereby discuss the consequence of universal physics i…
We discuss the mass modifications of $\bar{\mathrm{D}}$ and $\bar{\mathrm{D}}^{\ast}$ ($\mathrm{B}$ and $\mathrm{B}^{\ast}$) mesons in nuclear medium. The heavy quark symmetry for $\bar{\mathrm{D}}$ and $\bar{\mathrm{D}}^{\ast}$ ($\mathrm{B}$ and $\mathrm{B}^{\ast}$) mesons is adopted, and the interaction between a $\bar{\mathrm{D}}$ or $\bar{\mathrm{D}}^{\ast}$ ($\mathrm{B}$ or $\mathrm{B}^{\ast}$) meson and a nucleon is supplied from the pion exchange. We find the negative mass shifts for $\bar{\mathrm{D}}$ meson and $\mathrm{B}$ meson, and hence that the $\bar{\mathrm{D}}$ and $\mathrm{B}$ …
We make predictions for cross sections of $ρ$ and $ϕ$ vector meson photoproduction in ultraperipheral Xe-Xe collisions at $\sqrt{s_{NN}}=5.44$ TeV. Analyzing the momentum transfer distribution of $ρ$ mesons in this process, we explore the feasibility of extracting the nuclear density of $^{129}$Xe, which is needed in searches for dark matter with Xenon-based detectors.
We study the effect of the nucleon meson cloud on centrality dependence of the jet nuclear modification factor $R_{pA}$. We find that the meson-baryon Fock components may lead to a noticeable deviation of $R_{pA}$ from unity. Our results for $R_{pA}$ show the same tendency as that observed by ATLAS in $p+Pb$ collisions at $\sqrt{s}=5.02$ TeV. The meson cloud suppresses the central jet events and enhances the peripheral jet events. But quantitatively the effect is somewhat smaller than in the data.
The properties of open strange meson $K_1^\pm$ in nuclear matter are estimated in the QCD sum rule approach. We obtain a relation between the in-medium mass and width of $K_1^-$ ($K_1^+$) in nuclear matter, and show that the upper limit of the mass shift is as large as -249 (-35) MeV. The spectral modification of the $K_1$ meson is possible to be probed by using kaon beams at J-PARC. Such measurement together with that of $K^*$ will shed light on how chiral symmetry is partially restored in nuclear matter.
We investigate the bulk properties of symmetric nuclear matter within the framework of an in-medium modified chiral solitonic model with $π$, $ρ$ and $ω$ mesons. We consider the modification of meson degrees of freedom in nuclear matter, based on phenomenology of pion-nucleus scattering and the empirical nuclear mass formula. We discuss the results of the density dependence of the volume term in the mass formula and the incompressibility of symmetric nuclear matter, comparing them with relativistic mean-field models. The mass dropping of the $ρ$ meson in nuclear matter is also obtained and dis…
The planned experiments at FAIR enable the study of medium modifications of $D$ and $B$ mesons in (dense) nuclear matter. Evaluating QCD sum rules as a theoretical prerequisite for such investigations encounters heavy-light four-quark condensates. We utilize an extended heavy-quark expansion to cope with the condensation of heavy quarks.
We investigate the in-medium masses of a $\bar{D} (0^-)$ meson and a $\bar{D}_0^* (0^+)$ meson and spectral functions for $\bar{D}$ and $\bar{D}_0^*$ meson channels in nuclear matter. These mesons are introduced as chiral partner in the chiral symmetry broken vacuum, hence they are useful to explore the partial restoration of the broken chiral symmetry in nuclear matter. We consider the linear sigma model to describe the chiral symmetry breaking. Our study shows that the loop corrections to $\bar{D}$ and $\bar{D}_0^*$ meson masses provide a smaller mass splitting at finite density than that in…
Using the color glass condensate formalism, we study the nuclear modification of forward $J/ψ$ and $D$ meson production in high energy proton-nucleus collisions at the LHC. We show that relying on the optical Glauber model to obtain the dipole cross section of the nucleus from the one of the proton fitted to HERA DIS data leads to a smaller nuclear suppression than in the first study of these processes in this formalism and a better agreement with experimental data.
Spectral functions of the pseudoscalar $D$ meson in the nuclear medium are analyzed using QCD sum rules and the maximum entropy method. This approach enables us to extract the spectral functions without any phenomenological assumption, and thus to visualize in-medium modification of the spectral functions directly. It is found that the reduction of the chiral condensates of dimension 3 and 5 causes the masses of both $D^+$ and $D^-$ mesons to grow gradually at finite density. Additionally, we construct charge-conjugate-projected sum rules and find a $D^+$-$D^-$ mass splitting of about -15 MeV …
We expose the current experimental and theoretical situation of the interesting case of the production of phi mesons in up to very high energy collisions of hadrons on both nucleon and nuclear targets, and we present a quantitavely good theoretical description of the corresponding experimental data, based on the formalism of the well established Quark-Gluon String Model, that has proved to be valid for a wide energy range. All the available experimental data for phi-meson production in hadron-nucleon collisions on the spectra of secondary phi, and on the ratios of phi/pi(-) and phi/K(-) produc…
The rho meson spectral function in hot and dense asymmetric nuclear matter (number densities of proton and neutron different) is evaluated in an effective chiral SU(3) model within the mean field approximation (MFA). The dependence of the vector meson masses on density and temperature, their variation with the asymmetry parameter, the form of the spectral function when the p <-> n symmetry is broken are studied. One can observe clear splitting of the longitudinal and the transverse modes among the rho isospin multiplets. The role of a running tensor coupling on the spectral function is also st…
In this work we shall investigate the mass modifications of scalar mesons $\left( D_{0}, B_{0}\right)$,vector mesons $\left( D^{\ast}, B^{\ast}\right)$ and axial-vector mesons $\left(D_{1}, B_{1}\right)$ at finite density and temperature of the nuclear medium. The above mesons are modified in the nuclear medium through themodification of quark and gluon condensates. We shall find the medium modification of quark and gluon condensates within chiral SU(3) model through the medium modification of scalar-isoscalar fields $σ$ and $ζ$ at finite density and temperature. These medium modified quark an…
The existence of quark matter inside the cores of heavy neutron stars is a possibility which can be probed with modern astrophysical observations. We use an (axial)vector meson extended quark-meson model to describe quark matter in the core of neutron stars. We discover that an additional parameter constraint is necessary in the quark model to ensure chiral restoration at high densities. By investigating hybrid star sequences with various parameter sets we show that low sigma meson masses are needed to fulfill the upper radius constraints, and that the maximum mass of stable hybrid stars is on…
As a first step towards a realistic phenomenological description of vector and axial-vector mesons in nuclear matter, we calculate the spectral functions of the $ρ$ and the $a_1$ meson in a chiral baryon-meson model as a low-energy effective realization of QCD, taking into account the effects of fluctuations from scalar mesons, nucleons, and vector mesons within the Functional Renormalization Group (FRG) approach. The phase diagram of the effective hadronic theory exhibits a nuclear liquid-gas phase transition as well as a chiral phase transition at a higher baryon-chemical potential. The in-m…
We apply the nuclear model with explicit mesons to photoproduction of neutral pions off protons at the threshold. In this model the nucleons do not interact with each other via a potential but rather emit and absorb mesons that are treated explicitly on equal footing with the nucleons. We calculate the total cross section of the reaction for energies close to threshold and compare the calculations with available experimental data. We show that the model is able to reproduce the experimental data and determine the range of the parameters where the model is compatible with the experiment.
We propose to study the mass spectrum of the heavy-light mesons to probe the structure of the spin-isospin correlation in the nuclear medium. We point out that the spin-isospin correlation in the nuclear medium generates a mixing among the heavy-light mesons carrying different spins and isospins such as $D^+$, $D^0$, $D^{\ast +}$, and $D^{\ast 0}$ mesons. We use two types of correlations motivated by the skyrmion crystal and the chiral density wave as typical examples to obtain the mass splitting caused by the mixing. Our result shows that the structure of the mixing reflects the pattern of th…
