Showing papers on "Nuclear matter published in 2007"
TL;DR: In this article, the authors explore the properties of hadronic matter under extreme conditions of temperature and density, and the determination of the equation of state, the relation between pressure, temperature, and density of such matter.
383 citations
TL;DR: In this article, a comprehensive survey of the performance of one of the most successful non-relativistic self-consistent method, the Skyrme-Hartree-Fock model (SHF), with respect to these constraints is presented.
290 citations
TL;DR: In this article, the analysis of these atomic systems consists of fitting density-dependent optical potentials V opt = t ( ρ ) ρ to comprehensive sets of data of strong-interaction level shifts, widths and yields across the periodic table.
269 citations
TL;DR: In this paper, the Sakai-Sugimoto model at finite temperature and baryon chemical potential was analyzed and it was shown that the dominant phase has broken chiral symmetry.
Abstract: We analyze the phases of the Sakai-Sugimoto model at finite temperature and baryon chemical potential. Baryonic matter is represented either by 4-branes in the 8-branes or by strings stretched from the 8-branes to the horizon. We find the explicit configurations and use them to determine the phase diagram and equation of state of the model. The 4-brane configuration (nuclear matter) is always preferred to the string configuration (quark matter), and the latter is also unstable to density fluctuations. In the deconfined phase the phase diagram has three regions corresponding to the vacuum, quark-gluon plasma, and nuclear matter, with a first-order and a second-order phase transition separating the phases. We find that for a large baryon number density, and at low temperatures, the dominant phase has broken chiral symmetry. This is in qualitative agreement with studies of QCD at high density.
245 citations
TL;DR: In this paper, the Sakai-Sugimoto model at finite temperature and baryon chemical potential was analyzed and it was shown that the dominant phase has broken chiral symmetry.
Abstract: We analyze the phases of the Sakai-Sugimoto model at finite temperature and baryon chemical potential. Baryonic matter is represented either by 4-branes in the 8-branes or by strings stretched from the 8-branes to the horizon. We find the explicit configurations and use them to determine the phase diagram and equation of state of the model. The 4-brane configuration (nuclear matter) is always preferred to the string configuration (quark matter), and the latter is also unstable to density fluctuations. In the deconfined phase the phase diagram has three regions corresponding to the vacuum, quark-gluon plasma, and nuclear matter, with a first-order and a second-order phase transition separating the phases. We find that for a large baryon number density, and at low temperatures, the dominant phase has broken chiral symmetry. This is in qualitative agreement with studies of QCD at high density.
204 citations
TL;DR: In this paper, the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model is studied, which is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent exchange of scalar and vector mesons in the isoscalar and isovector channels.
196 citations
TL;DR: In this article, the pairing gap for cold Fermi atoms and low-density neutron matter as a function of the FermI momentum times the scattering length was studied. But the pairing gaps were not as large as those of cold atoms.
Abstract: Experiments with cold Fermi atoms can be tuned to probe strongly-interacting fluids that are very similar to the low-density neutron matter found in the crusts of neutron stars. In contrast to traditional superfluids and superconductors, matter in this regime is very strongly paired, with gaps of the order of the Fermi energy. We compute the $T=0$ equation of state and pairing gap for cold atoms and low-density neutron matter as a function of the Fermi momentum times the scattering length. Results of quantum Monte Carlo calculations show that the equations of state are very similar. The neutron matter pairing gap at low densities is found to be very large but, except at the smallest densities, significantly suppressed relative to cold atoms because of the finite effective range in the neutron-neutron interaction.
179 citations
TL;DR: The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is studied in this paper for studying the structure of systems as diverse as the neutron-rich nuclei and the neutron stars.
Abstract: The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is of significant importance for studying the structure of systems as diverse as the neutron-rich nuclei and the neutron stars. A number of reactions using the dynamical and the statistical models of multifragmentation, and the experimental isoscaling observable, are studied to extract information on the density dependence of the symmetry energy. It is observed that the dynamical and the statistical model calculations give consistent results assuming the sequential decay effect in dynamical model to be small. A comparison with several other independent studies is also made to obtain important constraints on the form of the density dependence of the symmetry energy. The comparison rules out an extremely ``stiff'' and ``soft'' forms of the density dependence of the symmetry energy with important implications for astrophysical and nuclear physics studies.
166 citations
TL;DR: In this paper, a hybrid equation of state (EoS) for dense matter is presented that satisfies phenomenological constraints from modern compact star (CS) observations which indicate high maximum masses (M ∼ 2 M ⊙ ) and large radii (R > 12 km ).
162 citations
TL;DR: In this article, the authors derived the collisional broadening of the meson's transverse momentum and the distortion of its intrinsic light cone wave function and showed that the medium-induced dissociation probability of heavy mesons is sensitive to the opacity of the quark-gluon plasma and the time dependence of its formation and evolution.
149 citations
TL;DR: In this paper, the Sakai-Sugimoto model of holographic QCD at zero temperature and finite chemical potential was studied and it was shown that as the baryon chemical potential is increased above a critical value, there is a phase transition to a nuclear matter phase characterized by a condensate of instantons on the probe Dbranes in the string theory dual.
Abstract: We study the Sakai-Sugimoto model of holographic QCD at zero temperature and finite chemical potential. We find that as the baryon chemical potential is increased above a critical value, there is a phase transition to a nuclear matter phase characterized by a condensate of instantons on the probe D-branes in the string theory dual. As a result of electrostatic interactions between the instantons, this condensate expands towards the UV when the chemical potential is increased, giving a holographic version of the expansion of the Fermi surface. We argue based on properties of instantons that the nuclear matter phase is necessarily inhomogeneous to arbitrarily high density. This suggests an explanation of the "chiral density wave" instability of the quark Fermi surface in large N_c QCD at asymptotically large chemical potential. We study properties of the nuclear matter phase as a function of chemical potential beyond the transition and argue in particular that the model can be used to make a semi-quantitative prediction of the binding energy per nucleon for nuclear matter in ordinary QCD.
TL;DR: In this paper, a new effective interaction PKA1 with \ensuremath{\rho}-tensor couplings for the density dependent relativistic Hartree-Fock (DDRHF) theory is presented.
Abstract: A new effective interaction PKA1 with \ensuremath{\rho}-tensor couplings for the density dependent relativistic Hartree-Fock (DDRHF) theory is presented. It is obtained by fitting selected empirical ground state and shell structure properties. It provides satisfactory descriptions of nuclear matter and the ground state properties of finite nuclei at the same quantitative level as recent DDRHF and relativistic mean field (RMF) models. Significant improvement in the single-particle spectra is also found due to the inclusion of \ensuremath{\rho}-tensor couplings. As a result, PKA1 cures a common disease of the existing DDRHF and RMF Lagrangians, namely, the artificial shells at 58 and 92, and recovers the realistic subshell closure at 64. Moreover, the proper spin-orbit splittings and well-conserved pseudospin symmetry are obtained with the new effective interaction PKA1. Due to the extra binding introduced by the \ensuremath{\rho}-tensor correlations, the balance between the nuclear attractions and the repulsions is changed, and this constitutes the physical reason for the improvement of the nuclear shell structure.
TL;DR: In this article, a formal recurrence relation approach to multiple parton scattering was used to find the complete solution to the problem of medium-induced gluon emission from partons propagating in cold nuclear matter.
Abstract: We use a formal recurrence relation approach to multiple parton scattering to find the complete solution to the problem of medium-induced gluon emission from partons propagating in cold nuclear matter. The differential bremsstrahlung spectrum, where Landau-Pomeranchuk-Migdal destructive interference effects are fully accounted for, is calculated for three different cases: (i) a generalization of the incoherent Bertsch-Gunion solution for asymptotic on-shell jets (ii) initial-state energy loss of incoming jets that undergo hard scattering, and (iii) final-state energy loss of jets that emerge out of a hard scatter. Our analytic solutions are given as an infinite opacity series, which represents a cluster expansion of the sequential multiple scattering. These new solutions allow, for the first time, direct comparison between initial- and final-state energy loss in cold nuclei. We demonstrate that, contrary to the naive assumption, energy loss in cold nuclear matter can be large. Numerical results to first order in opacity show that, in the limit of large jet energies, initial- and final-state energy losses exhibit different path length dependences, linear versus quadratic, in contrast to earlier findings. In addition, in this asymptotic limit, initial-state energy loss is considerably larger than final-state energy loss. These new results have significant implications for heavy-ionmore » phenomenology in both p+A and A+A reactions.« less
TL;DR: In this article, the authors examined the properties of inhomogeneous nuclear matter at sub-nuclear densities and showed that the size and shape of nuclei in neutron star matter at zero temperature is dependent on the density dependence of the symmetry energy.
Abstract: Department of Materials Science, Kochi University, Akebono-cho, Kochi 780-8520, Japan(Dated: February 9, 2008)We examine how the properties of inhomogeneous nuclear matter at subnuclear densities dependon the density dependence of the symmetry energy. Using a macroscopic nuclear model we calculatethe size and shape of nuclei in neutron star matter at zero temperature in a way dependent onthe density dependence of the symmetry energy. We find that for smaller symmetry energy atsubnuclear densities, corresponding to larger density symmetry coefficient L, the charge number ofnuclei is smaller, and the critical density at which matter with nuclei or bubbles becomes uniform islower. The decrease in the charge number is associated with the dependence of the surface tensionon the nuclear density and the density of a sea of neutrons, while the decrease in the critical densitycan be generally understood in terms of proton clustering instability in uniform matter.
TL;DR: In this paper, the density dependence of nuclear symmetry energy from different relativistic mean field models was determined, including nonlinear ones with meson field self-interactions, models with density-dependent meson-nucleon couplings, and point-coupling models without meson fields.
Abstract: Using various relativistic mean-field models, including nonlinear ones with meson field self-interactions, models with density-dependent meson-nucleon couplings, and point-coupling models without meson fields, we have studied the isospin-dependent bulk and single-particle properties of asymmetric nuclear matter. In particular, we have determined the density dependence of nuclear symmetry energy from these different relativistic mean-field models and compared the results with the constraints recently extracted from analyses of experimental data on isospin diffusion and isotopic scaling in intermediate energy heavy-ion collisions as well as from measured isotopic dependence of the giant monopole resonances in even-A Sn isotopes. Among the 23 parameter sets in the relativistic mean-field model that are commonly used for nuclear structure studies, only a few are found to give symmetry energies that are consistent with the empirical constraints. We have also studied the nuclear symmetry potential and the isospin splitting of the nucleon effective mass in isospin asymmetric nuclear matter. We find that both the momentum dependence of the nuclear symmetry potential at fixed baryon density and the isospin splitting of the nucleon effective mass in neutron-rich nuclear matter depend not only on the nuclear interactions but also on the definition of the nucleon optical potential.
TL;DR: For collisions involving more than approximately 80 participant nucleons, it is found that an extra suppression is present and this result is in qualitative agreement with previous Pb-Pb measurements by the NA50 experiment.
Abstract: The NA60 experiment studies muon pair production at the CERN Super Proton Synchrotron. In this Letter we report on a precision measurement of J/{psi} in In-In collisions. We have studied the J/{psi} centrality distribution, and we have compared it with the one expected if absorption in cold nuclear matter were the only active suppression mechanism. For collisions involving more than {approx}80 participant nucleons, we find that an extra suppression is present. This result is in qualitative agreement with previous Pb-Pb measurements by the NA50 experiment, but no theoretical explanation is presently able to coherently describe both results.
TL;DR: In this paper, an overview of the main methods used to determine the nucleus-nucleus optical potential (OP) is presented, which is the key to explore this interesting process.
Abstract: Elastic scattering of α-particles and some tightly bound light nuclei has shown the pattern of rainbow scattering at medium energies, which is due to the refraction of the incident wave by a strongly attractive nucleus–nucleus potential. This review gives an introduction to the physics of the nuclear rainbow based essentially on the optical model description of the elastic scattering. Since the realistic nucleus–nucleus optical potential (OP) is the key to explore this interesting process, an overview of the main methods used to determine the nucleus–nucleus OP is presented. Given the fact that the absorption in a rainbow system is much weaker than that usually observed in elastic heavy-ion scattering, the observed rainbow patterns were shown to be linked directly to the density overlap of the two nuclei penetrating each other in the elastic channel, with a total density reaching up to twice the nuclear matter saturation density ρ0. For the calculation of the nucleus–nucleus OP in the double-folding model, a realistic density dependence has been introduced into the effective M3Y interaction which is based originally on the G-matrix elements of the Reid and Paris nucleon–nucleon (NN) potentials. Most of the elastic rainbow scattering data were found to be best described by a deep real OP like the folded potential given by this density-dependent M3Y interaction. Within the Hartree–Fock formalism, the same NN interaction gives consistently a soft equation of state of cold nuclear matter which has an incompressibility constant K≈ 230–260 MeV. Our folding analysis of numerous rainbow systems has shown that the elastic α-nucleus and nucleus–nucleus refractive rainbow scattering is indeed a very helpful experiment for the determination of the realistic K value. The refractive rainbow-like structures observed in other quasi-elastic scattering reactions have also been discussed. Some evidences for the refractive effect in the elastic scattering of unstable nuclei are presented and perspectives for future studies are discussed.
TL;DR: The spatial structure of the two-neutron wave function in the Borromean nucleus (11)Li is investigated, using a three-body model of (9)Li + n + n, which includes many-body correlations stemming from the Pauli principle, to establish a strong concentration of the neutron pair on the nuclear surface for neutron-rich nuclei for the first time.
Abstract: We investigate the spatial structure of the two-neutron wave function in the Borromean nucleus {sup 11}Li, using a three-body model of {sup 9}Li+n+n, which includes many-body correlations stemming from the Pauli principle. The behavior of the neutron pair at different densities is simulated by calculating the two-neutron wave function at several distances between the core nucleus {sup 9}Li and the center of mass of the two neutrons. With this representation, a strong concentration of the neutron pair on the nuclear surface is for the first time quantitatively established for neutron-rich nuclei. That is, the neutron pair wave function in {sup 11}Li has an oscillatory behavior at normal density, while it becomes a well-localized single peak in the dilute density region around the nuclear surface. We point out that these features qualitatively correspond to the BCS- and BEC-like structures of the pair wave function found in infinite nuclear matter.
TL;DR: In this article, the parity doublet model was used to model the chiral phase transition of nuclear matter in a SU(2) linear sigma model at zero-temperature.
Abstract: We study dense nuclear matter and the chiral phase transition in a SU(2) parity doublet model at zero temperature. The model is defined by adding the chiral partner of the nucleon, the N{sup '}, to the linear sigma model, treating the mass of the N{sup '} as an unknown free parameter. The parity doublet model gives a reasonable description of the properties of cold nuclear matter, and avoids unphysical behavior present in the standard SU(2) linear sigma model. If the N{sup '} is identified as the N{sup '}(1535), the parity doublet model shows a first order phase transition to a chirally restored phase at large densities, {rho}{approx_equal}10{rho}{sub 0}, defining the transition by the degeneracy of the masses of the nucleon and the N{sup '}. If the mass of the N{sup '} is chosen to be 1.2 GeV, then the critical density of the chiral phase transition is lowered to three times normal nuclear matter density, and for physical values of the pion mass, the first order transition turns into a smooth crossover.
TL;DR: In this paper, it was shown that the nuclear symmetry energy is the key quantity in the stability consideration in neutron star matter and that the symmetry energy controls the position of crust-core transition and also may lead to new effects in the inner core of neutron star.
Abstract: It is shown that the nuclear symmetry energy is the key quantity in the stability consideration in neutron star matter. The symmetry energy controls the position of crust-core transition and also may lead to new effects in the inner core of neutron star.
TL;DR: In this article, the temperature and density-dependent symmetry energy coefficients of moderate-temperature nuclear gases produced in the violent collisions of 35 MeV/nucleon Zn-64 projectiles with Mo-92 and Au-197 target nuclei reveal a large degree of alpha particle clustering at low densities.
Abstract: Experimental analyses of moderate-temperature nuclear gases produced in the violent collisions of 35 MeV/nucleon Zn-64 projectiles with Mo-92 and Au-197 target nuclei reveal a large degree of alpha particle clustering at low densities. For these gases, temperature- and density-dependent symmetry energy coefficients have been derived from isoscaling analyses of the yields of nuclei with A <= 4. At densities of 0.01 to 0.05 times the ground-state density of symmetric nuclear matter, the temperature- and density-dependent symmetry energies range from 9.03 to 13.6 MeV. This is much larger than those obtained in mean-field calculations and reflects the clusterization of low-density nuclear matter. The results are in quite reasonable agreement with calculated values obtained with a recently proposed virial equation of state calculation.
TL;DR: In this paper, the authors studied the properties of nonrotating and rotating neutron stars for a new set of equations of state (EOSs) with different high-density behavior obtained using the extended field theoretical model.
Abstract: We study the properties of nonrotating and rotating neutron stars for a new set of equations of state (EOSs) with different high-density behavior obtained using the extended field theoretical model. The high-density behavior for these EOSs are varied by varying the {omega}-meson self-coupling and hyperon-meson couplings in such a way that the quality of fit to the bulk nuclear observables, nuclear matter incompressibility coefficient, and hyperon-nucleon potential depths remain practically unaffected. We find that the largest value for maximum mass for the nonrotating neutron star is 2.1M{sub {center_dot}}. The radius for a neutron star with canonical mass is 12.8-14.1 km, provided only those EOSs are considered for which the maximum mass is larger than 1.6M{sub {center_dot}}, the lower bound on the maximum mass measured so far. Our results for the very recently discovered fastest rotating neutron star indicate that this star is supramassive with mass 1.7M{sub {center_dot}}-2.7M{sub {center_dot}} and circumferential equatorial radius 12-19 km.
TL;DR: In this paper, the authors generalize the statistical multifragmentation model, previously successfully used for the description of experimental data, for the case of hypernuclear systems and predict relative yields of hypernuclei and the main characteristics of such a breakup.
Abstract: In peripheral collisions of relativistic heavy ions highly excited spectators containing \ensuremath{\Lambda} hyperons can be produced. Such strange spectator matter may undergo a break-up into many fragments (multifragmentation) as it is well established for ordinary nuclear systems. We generalize the statistical multifragmentation model, previously successfully used for the description of experimental data, for the case of hypernuclear systems. We predict relative yields of hypernuclei and the main characteristics of such a breakup. We point at a connection of this phenomenon with a liquid-gas phase transition in hypermatter.
TL;DR: In this paper, a Skyrme-Lyon mean-field approach was used to characterize the free-energy curvature of a nuclear matter composed of neutrons, protons and electrons.
TL;DR: In this article, the Dirac-Brueckner-Hartree-Fock equation of state for isospin asymmetric nuclear matter has been used to construct a density-dependent relativistic mean-field theory, which can be applied to finite nuclei.
Abstract: We present Dirac-Brueckner-Hartree-Fock calculations for isospin asymmetric nuclear matter which are based on improved approximations schemes. The potential matrix elements have been adapted for isospin asymmetric nuclear matter in order to account for the proton-neutron mass splitting in a more consistent way. The proton properties are particularly sensitive to this adaption and its consequences, whereas the neutron properties remains almost unaffected in neutron-rich matter. Although at present full Brueckner calculations are still too complex to apply to finite nuclei, these relativistic Brueckner results can be used as a guidance to construct a density-dependent relativistic mean-field theory, which can be applied to finite nuclei. It is found that an accurate reproduction of the Dirac-Brueckner-Hartree-Fock equation of state requires a renormalization of these coupling functions.
TL;DR: In this article, the properties of inhomogeneous nuclear matter are investigated considering the self-consistent Skyrme-Hartree-Fock approach with inclusion of pairing correlations, and a comparison is made to results obtained within the Thomas-Fermi approximation.
Abstract: The properties of inhomogeneous nuclear matter are investigated considering the self-consistent Skyrme-Hartree-Fock approach with inclusion of pairing correlations. For a comparison we also consider a relativistic mean-field approach. The inhomogeneous infinite matter is described in terms of cubic Wigner-Seitz cells, which leads to a smooth transition to the limit of homogeneous nuclear matter. The possible existence of various structures in the so-called pasta phase is investigated within this self-consistent approach and a comparison is made to results obtained within the Thomas-Fermi approximation. Results for the proton abundances and the pairing properties are discussed for densities for which clustering phenomena are obtained.
TL;DR: Comparisons between theory and experiment for multihadron observables in both confining and deconfined media offer comprehensive evidence for partonic energy loss as the mechanism of jet modification in dense matter.
Abstract: Medium modification of dihadron fragmentation functions due to gluon bremsstrahlung induced by multiple partonic scattering is studied in both deep-inelastic scattering (DIS) off large nuclei and high-energy heavy-ion collisions within the same framework of twist expansion. The modification for dihadrons is found to closely follow that for single hadrons, leading to a weak nuclear suppression of their ratios in DIS experiments. A mild enhancement of the near-side correlation of two high transverse momentum hadrons with increasing centrality is found in heavy-ion collisions due to trigger bias and the rise in parton energy loss with centrality. Successful comparisons between theory and experiment for multihadron observables in both confining and deconfined media offer comprehensive evidence for partonic energy loss as the mechanism of jet modification in dense matter.
TL;DR: In this paper, a hybrid equation of state (EoS) for dense matter is presented, in which a nuclear matter phase is described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach and a two-flavor quark phase is modelled according to a recently developed covariant, nonlocal chiral quark model.
Abstract: We present a hybrid equation of state (EoS) for dense matter in which a nuclear matter phase is described within the Dirac-Brueckner-Hartree-Fock (DBHF) approach and a two-flavor quark matter phase is modelled according to a recently developed covariant, nonlocal chiral quark model. We show that modern observational constraints for compact star masses (M{approx}2M{sub {center_dot}}) can be satisfied when a small vector-like four quark interaction is taken into account. The corresponding isospin symmetric EoS is consistent with flow data analyses of heavy ion collisions and points to a deconfinement transition at about 0.55 fm{sup -3}.
TL;DR: In this paper, the influence of dispersive self-energy effects, three-body forces, and polarization contributions to the interaction kernel on the {sup 1}S{sub 0} proton pairing in neutron star matter was studied.
Abstract: We studied the influence of dispersive self-energy effects, three-body forces, and polarization contributions to the interaction kernel on the {sup 1}S{sub 0} proton pairing in neutron star matter. We found that a strong suppression of the gap by self-energy effects and three-body forces is at low density compensated by the attractive polarization interaction, shifting the domain of pairing to below {rho}{sub B}{approx_equal}0.3 fm{sup -3}.
TL;DR: In this article, a study of the charge and matter densities and the corresponding rms radii for even-even isotopes of Ni, Kr, and Sn has been performed in the framework of the deformed self-consistent mean-field Skyrme HF+BCS method.
Abstract: A study of the charge and matter densities and the corresponding rms radii for even-even isotopes of Ni, Kr, and Sn has been performed in the framework of the deformed self-consistent mean-field Skyrme HF+BCS method. The resulting charge radii and neutron skin thicknesses of these nuclei are compared with available experimental data, as well as with other theoretical predictions. The formation of a neutron skin, which manifests itself in an excess of neutrons at distances greater than the radius of the proton distribution, is analyzed in terms of various definitions. Formation of a proton skin is shown to be unlikely. The effects of deformation on the neutron skins in even-even deformed nuclei far from the stability line are discussed.