High Temperature Nuclear Matter Research Articles

Equation of state for β-stable hot nuclear matter

We provide an equation of state for hot nuclear matter in β-equilibrium by applying a momentum-dependent effective interaction. We focus on the study of the equation of state of high-density and high-temperature nuclear matter, containing leptons (electrons and muons) under the chemical equilibrium condition in which neutrinos have left the system. Special attention is dedicated to the study of the contribution of the components of β-stable nuclear matter to the entropy per particle, a quantity of great interest for the study of structure and collapse of supernova.

Quarkonium measurements in the STAR experiment

Abstract Calculations of Quantum Chromodynamics on lattice showed that under conditions of high energy density or high temperature nuclear matter undergoes a phase transition from a state of quarks and gluons confined in hadrons to a deconfined state, the Quark–Gluon Plasma (QGP). Such conditions were present in first moments after the Big Bang and can be created in laboratory by colliding of heavy ions with sufficient energy. One of the most prominent signatures of QGP formation is the quarkonium suppression in central heavy-ion collisions arising from the Debye screening of the quark–antiquark potential in hot and dense nuclear matter. However, cold nuclear matter effects and heavy quark recombination could influence the measured quarkonium yields. Measurements of J / ψ at different collision energies can shed new light on understanding the interplay of these mechanisms for J / ψ production. The production mechanism of J / ψ is not well understood yet and the simultaneous measurement of J / ψ transverse momentum spectra and polarization in p + p collisions can significantly constrain possible production scenarios. In this proceedings, we report the recent STAR measurements of J / ψ production at mid-rapidity in p + p , d + Au , Au + Au at s NN = 200 GeV and in Au + Au collisions at s NN = 39 GeV and s NN = 62 GeV .

EQUATION OF STATE FOR DENSE SUPERNOVA MATTER

We provide an equation of state for high density supernova matter by applying a momentum-dependent effective interaction. We focus on the study of the equation of state of high density and high temperature nuclear matter containing leptons (electrons and neutrinos) under the chemical equilibrium condition. The conditions of charge neutrality and equilibrium under the β-decay process lead first to the evaluation of the lepton fractions and afterward to the evaluation of internal energy, pressure, entropy and, in total to the equation of state of hot nuclear matter for various isothermal cases. Thermal effects on the properties and equation of state of nuclear matter are evaluated and analyzed in the framework of the proposed effective interaction model. Since supernova matter is characterized by a constant entropy, we also present the thermodynamic properties for the isentropic case. Special attention is devoted to the study of the contribution of the components of β-stable nuclear matter to the entropy per particle, a quantity of great interest for the study of structure and collapse of supernovas.

Equation of state forβ-stable hot nuclear matter

We provide an equation of state for hot nuclear matter in $\ensuremath{\beta}$ equilibrium by applying a momentum-dependent effective interaction. We focus on the study of the equation of state of high-density and high-temperature nuclear matter, containing leptons (electrons and muons) under the chemical equilibrium condition in which neutrinos have left the system. The conditions of charge neutrality and equilibrium under the $\ensuremath{\beta}$-decay process lead first to the evaluation of proton and lepton fractions and then to the evaluation of internal energy, free energy, and pressure, and in total to the equation of state of hot nuclear matter. Thermal effects on the properties and equation of state of nuclear matter are assessed and analyzed in the framework of the proposed effective interaction model. Special attention is given to the study of the contribution of the components of $\ensuremath{\beta}$-stable nuclear matter to the entropy per particle, a quantity of great interest in the study of structure and collapse of supernova.

Photon rates for heavy-ion collisions from hidden local symmetry

We study photon production from the hidden local symmetry approach that includes {pi}, {rho}, and a{sub 1} mesons and compute the corresponding photon emission rates from a hadronic gas in thermal equilibrium. Together with experimental radiative decay widths of the background, these rates are used in a relativistic transport model to calculate single photon spectra in heavy-ion collisions at SPS energies. We then employ this effective theory to test three scenarios for the chiral phase transition in high-temperature nuclear matter including decreasing vector meson masses. Although all calculations respect the upper bound set by the WA80 Collaboration, we find the scenarios could be distinguished with more detailed data. {copyright} {ital 1998} {ital The American Physical Society}

Linear sigma model with parity doubling

Recent lattice-gauge-theory simulations at finite temperatures have suggested that chiral-symmetry restoration at finite temperatures entails parity doubling of the baryon spectrum. We show that a natural extension of the Gell-Mann--L\'evy model incorporates this effect. Predictions of this candidate effective model for the hadronic component of high-density and high-temperature nuclear matter are discussed. The model suggests a parametrization of the dependence of the baryon-doublet masses on the quark mass. This parametrization is compared with the recent lattice results.

Dileptons as a probe of pion, kaon, nucleon, and antinucleon dynamics in nuclear matter.

We continue our study of dilepton radiation from high-temperature nuclear matter by computing the rates for the annihilations ${K}^{+}$${K}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ and NN\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$. In general this radiation would yield information on the abundances of kaons and antinucleons in hot and dense nuclear matter. More specifically, the former may yield information on the approach to kaon condensation, and the latter may yield information on the nucleon-antinucleon dispersion relations as predicted by relativistic field theories of nuclear matter. However, these yields are mostly overshadowed by the processes np\ensuremath{\rightarrow}${\mathrm{npe}}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ and ${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$, so that dilepton production remains essentially a probe of pion dynamics in the nuclear medium.

Electron-positron pair production in high temperature nuclear matter

The general features of electron-positron emission from high temperature nuclear matter are discussed. Estimates are made of the production rates arising from incoherent nucleon-nucleon scattering and from two pion annihilation. It may be possible to infer the pion dispersion relation in hot and dense nuclear matter by measuring the invariant mass distribution of back-to-back electrons and positrons in the center of mass frame in high energy nucleus-nucleus collisions.

Dilepton radiation from high temperature nuclear matter.

The general features of electron-positron emission from high temperature nuclear matter are discussed. Estimates are made of the production rates arising from incoherent nucleon-nucleon scattering and from two-pion annihilation. It may be possible to infer the pion dispersion relation in hot and dense nuclear matter by measuring the invariant mass distribution of back-to-back electrons and positrons in the center of mass frame in high energy nucleus-nucleus collisions.