Nuclear Theory·nucl-th

Wednesday·November 23, 2016

16 papers—9 primary·7 cross-listed

01
Effects of Induced Surface Tension in Nuclear and Hadron Matter
V.V. Sagun🇺🇦 · K.A. Bugaiev🇺🇦 · A.I. Ivanytskyi🇺🇦 · D.R. Oliinychenko🇺🇦 · I.N. Mishustin🇩🇪
Short range particle repulsion is rather important property of the hadronic and nuclear matter equations of state. We present a novel equation of state which is based on the virial expansion for the multicomponent mixtures with hard-core repulsion. In addition to the hard-core repulsion taken into account by the proper volumes of particles, this equation of state explicitly contains the surface tension which is induced by another part of the hard-core repulsion between particles. At high densities the induced surface tension vanishes and the excluded volume treatment of hard-core repulsion is switched to its proper volume treatment. Possible applications of this equation of state to a description of hadronic multiplicities measured in A+A collisions, to an investigation of the nuclear matter phase diagram properties and to the neutron star interior modeling are discussed.
nucl-thastro-ph.HEhep-phEPJ Web Conf.(2017)·13 citations
02
Symmetry Parameter Constraints From A Lower Bound On The Neutron-Matter Energy
Ingo Tews🇺🇸 · James M. Lattimer🇺🇸 · Akira Ohnishi🇯🇵 · Evgeni E. Kolomeitsev🇸🇰
We propose the existence of a lower bound on the energy of pure neutron matter (PNM) on the basis of unitary-gas considerations. We discuss its justification from experimental studies of cold atoms as well as from theoretical studies of neutron matter. We demonstrate that this bound results in limits to the density-dependent symmetry energy, which is the difference between the energies of symmetric nuclear matter and PNM. In particular, this bound leads to a lower limit to the volume symmetry energy parameter $S_{0}$ . In addition, for assumed values of $S_{0}$ above this minimum, this bound implies both upper and lower limits to the symmetry energy slope parameter $L$ , which describes the lowest-order density dependence of the symmetry energy. A lower bound on the neutron-matter incompressibility is also obtained. These bounds are found to be consistent with both recent calculations of the energies of PNM and constraints from nuclear experiments. Our results are significant because several equations of state that are currently used in astrophysical simulations of supernovae and neutron star mergers, as well as in nuclear physics simulations of heavy-ion collisions, have symmetry energy parameters that violate these bounds. Furthermore, below the nuclear saturation density, the bound on neutron-matter energies leads to a lower limit to the density-dependent symmetry energy, which leads to upper limits to the nuclear surface symmetry parameter and the neutron-star crust-core boundary. We also obtain a lower limit to the neutron-skin thicknesses of neutron-rich nuclei. Above the nuclear saturation density, the bound on neutron-matter energies also leads to an upper limit to the symmetry energy, with implications for neutron-star cooling via the direct Urca process.
nucl-thastro-ph.HEcond-mat.quant-gasApJ(2017)·319 citations
03
Lepton production cross sections in quasielastic $ν / ν ˉ -$ A scattering
M. Sajjad Athar🇮🇳 · F. Akbar🇮🇳 · M. Rafi Alam🇮🇳 · S. Chauhan🇮🇳 · S. K. Singh🇮🇳 · F. Zaidi🇮🇳
We present the results of (anti)neutrino induced CCQE cross sections from some nuclear targets in the energy region of $E_{ν} \leq 1 G e V$ . The aim of the study is to confront electron and muon production cross sections relevant for $ν_{μ} \leftrightarrow ν_{e}$ or $ν ˉ_{μ} \leftrightarrow ν ˉ_{e}$ oscillation experiments. The effects due to lepton mass and its kinematic implications, second class currents and uncertainties in the axial and pseudoscalar form factors are discussed for (anti)neutrino induced reaction cross sections on free nucleon as well as the nucleons bound in a nucleus where nuclear medium effects influence the cross section. The calculations have been performed using local Fermi gas model with nucleon correlation effects. The details are given in Ref.[1].
nucl-th2 citations
04
Medium effects in the deep-inelastic charged lepton/neutrino-A scattering
H. Haider🇮🇳 · F. Zaidi🇮🇳 · M. Sajjad Athar🇮🇳 · S. K. Singh🇮🇳 · I. Ruiz Simo🇪🇸
In this work, we have discussed the recent developments that have taken place to understand the differences in the weak $F_{2 A}^{W e ak} (x, Q^{2})$ and electromagnetic $F_{2 A}^{E M} (x, Q^{2})$ nuclear structure functions. Also we present the results of our work on nuclear medium effects on $F_{2 A}^{W e ak} (x, Q^{2})$ and $F_{2 A}^{E M} (x, Q^{2})$ for a wide range of $x$ and $Q^{2}$ . These results have been obtained using a microscopic nuclear model, where to incorporate nuclear medium effects, Fermi motion, binding energy, nucleon correlations, mesonic contributions from pion and rho mesons and shadowing effects are considered. The calculations are performed in local density approximation using relativistic nucleon spectral function. We have also compared the theoretical results with the recent experimental data on electromagnetic and weak structure functions. Furthermore, we have studied the nuclear medium effects in Drell-Yan(DY) process and present the results for differential cross section, and the results are compared with the data of E772 experiment.
nucl-th0 citations
05
Forward-backward correlations between intensive observables
Vladimir Kovalenko🇷🇺 · Vladimir Vechernin (Saint Petersburg State University, Russia)🇷🇺
We demonstrate that the investigations of the forward-backward correlations between intensive observables enable to obtain more clear signal about the initial stage of hadronic interaction, e.g. about the process of string fusion, compared to usual forward-backward multiplicity correlations. As an example, the correlation between mean-event transverse momenta of charged particles in separated rapidity intervals is considered. We performed calculations in the framework of dipole-based Monte Carlo string fusion model. We obtained the dependence of the correlation strength on the collision centrality for different initial energies and colliding systems. It is shown that the dependence reveals the decline of the correlation coefficient for most central Pb-Pb collisions at LHC energy. We compare the results both with the ones obtained in alternative models and with the ones obtained by us using various MC generators.
nucl-thhep-phJ.Phys.Conf.Ser.(2017)·12 citations
06
Hadron Resonance Gas Model for An Arbitrarily Large Number of Different Hard-Core Radii
K. A. Bugaev · V. V. Sagun · A. I. Ivanytskyi · I. P. Yakimenko · E. G. Nikonov · A.V. Taranenko · G. M. Zinovjev
We develop a novel formulation of the hadron-resonance gas model which, besides a hard-core repulsion, explicitly accounts for the surface tension induced by the interaction between the particles. Such an equation of state allows us to go beyond the Van der Waals approximation for any number of different hard-core radii. A comparison with the Carnahan-Starling equation of state shows that the new model is valid for packing fractions 0.2-0.22, while the usual Van der Waals model is inapplicable at packing fractions above 0.1-0.11. Moreover, it is shown that the equation of state with induced surface tension is softer than the one of hard spheres and remains causal at higher particle densities. The great advantage of our model is that there are only two equations to be solved and it does not depend on the various values of the hard-core radii used for different hadronic resonances. Using this novel equation of state we obtain a high-quality fit of the ALICE hadron multiplicities measured at center-of-mass energies of 2.76 TeV per nucleon. Furthermore, using the traditional hadron-resonance gas model with multi-component hard-core repulsion and the novel one we investigate the recently suggested model in which the proper volume of a hadron is proportional to its mass. We find that the high-temperature maximum of $χ^{2} / n df$ observed in the latter model always appears in the region located far above the limit of its applicability.
nucl-thhep-ph7 citations
07
The Peak Structure in the In-Flight $^{3} He (K^{-}, Λ p) n$ Reaction Around the $K ˉ N N$ Threshold
Takayasu Sekihara (JAEA, Ibaraki)🇯🇵 · Eulogio Oset (Valencia U. amd Valencia U., IFIC)🇪🇸 · Angels Ramos (Barcelona U. and ICC, Barcelona U.)🇪🇸
We theoretically investigate the origin of the peak structure around the $K^{-} pp$ threshold observed in the in-flight $^{3} He (K^{-}, Λ p) n$ reaction in the recent E15 experiment at J-PARC. For this purpose, we consider two scenarios to produce the peak. One is that the $Λ (1405)$ is generated but it does not correlate with $p$ , and the uncorrelated $Λ (1405) p$ system subsequently decays into $Λ p$ . The other one is that the $K ˉ N N$ bound state is indeed generated and decays into $Λ p$ . As a result, the experimental signal is qualitatively well reproduced in the $K ˉ N N$ bound scenario, definitely discarding the uncorrelated $Λ (1405) p$ one.
nucl-thhep-phnucl-exJPS Conf.Proc.(2017)·2 citations
08
Leading Neutrons From Polarized Proton-Nucleus Collisions
B. Z. Kopeliovich🇨🇱 · I. K. Potashnikova🇨🇱 · Ivan Schmidt🇨🇱
Leading neutron production on protons is known to be subject to strong absorptive corrections, which have been under debate for a long time. On nuclear targets these corrections are significantly enhanced and push the partial cross sections of neutron production to the very periphery of the nucleus. As a result, the A-dependences of inclusive and diffractive neutron production turn out to be similar. The mechanism of \pi-a_1 interference, which successfully explained the observed single-spin asymmetry of neutrons in polarized pp interactions, is extended here to polarized pA collisions. Corrected for nuclear effects it explains well the magnitude and sign of the asymmetry A_N observed in inelastic events, resulting in a violent break up of the nucleus. However the excessive magnitude of A_N observed in the diffractive sample, remains a challenge.
nucl-thhep-phAIP Conf.Proc.(2017)·4 citations
09
On the Origin of the Elliptic Flow and its Dependence on the Equation of State in Heavy Ion Reactions at Intermediate Energies
A. Le Fevre🇩🇪 · Y. Leifels🇩🇪 · C. Hartnack🇫🇷 · J. Aichelin🇫🇷
Recently it has been discovered that the elliptic flow, v2, of composite charged particles emitted at midrapidity in Heavy-Ion collisions at intermediate energies shows the strongest sensitivity to the Nuclear Equation of State (EoS) which has been observed up to now within a microscopic model. This dependence on the nuclear EoS is predicted by Quantum Molecular Dynamics (QMD) calculations [1] which show as well that the absorption or rescattering of in-plane emitted particles by the spectator matter is not the main reason for the EoS dependence of the elliptic flow at mid-rapidity but different density gradients (and therefore different forces) in the direction of the impact parameter (x-direction) as compared to the direction perpendicular to the reaction plan (y-direction), caused by the presence of the spectator matter. The stronger density gradient in y-direction accelerates the particles more and creates therefore a negative v2. When using a soft momentum dependent EoS, the QMD calculations reproduce the experimental results.
nucl-thPRC(2018)·57 citations

Affiliations

first authorsco-authorsvia INSPIRE