Nuclear Theory·nucl-th

Tuesday·January 12, 2016

14 papers—9 primary·5 cross-listed

01
[Submitted on 10 Jan 2016]
Neutron Skins and Halo Orbits in the $s d$ and $p f$ shells
J. Bonnard🇮🇹 · S. M. Lenzi🇮🇹 · A. P. Zuker🇮🇹
The strong dependence of Coulomb energies on nuclear radii makes it possible to extract the latter from calculations of the former. The resulting estimates of neutron skins indicate that two mechanisms are involved. The first one---isovector monopole polarizability---amounts to noting that when a particle is added to a system it drives the radii of neutrons and protons in different directions, tending to equalize the radii of both fluids independently of the neutron excess. This mechanism is well understood and the Duflo-Zuker (small) neutron skin values derived 14 years ago are consistent with recent measures and estimates. The alternative mechanism involves halo orbits whose huge sizes tend to make the neutron skins larger and have a subtle influence on the radial behavior of $s d$ and $p f$ shell nuclei. In particular, they account for the sudden rise in the isotope shifts of nuclei beyond $N = 28$ and the near constancy of radii in the $A = 40 - 56$ region. This mechanism, detected here for the first time, is not well understood and may well go beyond Efimov physics usually associated to halo orbits.
Comments:
4 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.02168 [pdf]
PRL(2016)·32 citations
02
[Submitted on 10 Jan 2016]
Hydrodynamic fluctuations and dissipation in an integrated dynamical model
Koichi Murase🇯🇵 · Tetsufumi Hirano🇯🇵
We develop a new integrated dynamical model to investigate the effects of the hydrodynamic fluctuations on observables in high-energy nuclear collisions. We implement hydrodynamic fluctuations in a fully 3-D dynamical model consisting of the hydrodynamic initialization models of the Monte-Carlo Kharzeev-Levin-Nardi model, causal dissipative hydrodynamics and the subsequent hadronic cascades. By analyzing the hadron distributions obtained by massive event-by-event simulations with both of hydrodynamic fluctuations and initial-state fluctuations, we discuss the effects of hydrodynamic fluctuations on the flow harmonics, $v_{n}$ and their fluctuations.
Comments:
4 pages, 4 figures, Proceedings of the XXV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2015)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1601.02260 [pdf]
NPA(2016)·52 citations
03
[Submitted on 11 Jan 2016]
Establishing mass spectrum of $S = - 1$ hyperon resonances via a dynamical coupled-channels analysis of $K^{-} p$ reactions
Hiroyuki Kamano🇯🇵
We report our recent effort for the extraction of resonance parameters (complex pole mass and residues etc.) associated with Lambda* and Sigma* hyperons. This was accomplished via a comprehensive partial-wave analysis of the data for K^- p --> barK N, pi Sigma, pi Lambda, eta Lambda, K Xi reactions from the thresholds up to W=2.1 GeV within a dynamical coupled-channels approach. The results suggest a possible existence of new narrow J^P=3/2^+ \Lambda resonance with pole mass 1671^{+2}_{-8} -i(5^{+11}_{-2}) MeV, located close to the eta Lambda threshold. This resonance is found to be responsible for reproducing the data for K^-p --> eta Lambda differential cross sections near the threshold, and thus the data seem favor its existence. The extracted poles for J^P=1/2^- Lambda resonances below the barK N threshold, including Lambda(1405), are also presented.
Comments:
4 pages, 2 figures. Contribution to the proceedings of The 12th International Conference on Hypernuclear and Strange Particle Physics (HYP2015), Sendai, Japan, September 7-12, 2015
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1601.02322 [pdf]
JPS Conf.Proc.(2017)·0 citations
04
[Submitted on 11 Jan 2016]
Fixed points of the SRG evolution and the on-shell limit of the nuclear force
E. Ruiz Arriola🇪🇸 · S. Szpigel🇧🇷 · V. S. Timoteo🇧🇷
We study the infrared limit of the similarity renormalization group (SRG) using a simple toy model for the nuclear force aiming to investigate the fixed points of the SRG evolution with both the Wilson and the Wegner generators. We show how a fully diagonal interaction at the similarity cutoff $λ \to 0$ may be obtained from the eigenvalues of the hamiltonian and quantify the diagonalness by means of operator norms. While the fixed points for both generators are equivalent when no bound-states are allowed by the interaction, the differences arising from the presence of the Deuteron bound-state can be disentangled very clearly by analyzing the evolved interactions in the infrared limit $λ \to 0$ on a finite momentum grid. Another issue we investigate is the location on the diagonal of the hamiltonian in momentum-space where the SRG evolution places the Deuteron bound-state eigenvalue once it reaches the fixed point. This finite momentum grid setup provides an alternative derivation of the celebrated trace identities, as a by product. The different effects due to either the Wilson or the Wegner generators on the binding energies of $A = 2, 3, 4$ systems are investigated and related to the ocurrence of a Tjon-line which emerges as the minimum of an avoided crossing between $E_{α} = 4 E_{t} - 3 E_{d}$ and $E_{α} = 2 E_{t}$ . All infrared features of the flow equations are illustrated using the toy model for the two-nucleon $S$ -waves.
Comments:
39 pages, 17 figures, revised version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1601.02360 [pdf]
Annals Phys.(2016)·15 citations
05
[Submitted on 11 Jan 2016]
Hartree-Fock and Random Phase Approximation theories in a many-fermion solvable model
Giampaolo Co' · Stefano De Leo
We present an ideal system of interacting fermions where the solutions of the many-body Schroedinger equation can be obtained without making approximations. These exact solutions are used to test the validity of two many-body effective approaches, the Hartree-Fock and the Random Phase Approximation theories. The description of the ground state done by the effective theories improves with increasing number of particles.
Comments:
17 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.02418 [pdf]
Mod.Phys.Lett.A(2015)·10 citations
06
[Submitted on 5 Jan 2016]
Nonclassical Particle Transport in the 1-D Diffusive Limit
Richard Vasques · Rachel Slaybaugh · Kai Krycki
This paper provides numerical results that demonstrate the validity of the nonclassical diffusion approximation to the nonclassical transport equation in certain 1-D diffusive systems. This result provides a more solid foundation in which to improve this theory for relevant nuclear applications.
Comments:
9 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.02495 [pdf]
Trans.Amer.Nucl.Soc.(2016)·3 citations
07
[Submitted on 11 Jan 2016]
Energetic Light Fragment Production Capability in MCNP6
Leslie M. Kerby · Stepan G. Mashnik · Konstantin K. Gudima · Arnold J. Sierk · Jeffrey S. Bull · Michael R. James
The goal of this research is to enable MCNP6 to produce high-energy light fragments. These energetic light fragments may be emitted by our models through three processes: Fermi breakup, preequilibrium, and coalescence. We explore the emission of light fragments through each of these mechanisms and demonstrate an improved agreement with experimental data achieved by extending precompound models to include emission of fragments heavier than $^{4}$ He.
Comments:
To be published in Transactions of the American Nuclear Society, 2016
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1601.02537 [pdf]
0 citations
08
[Submitted on 11 Jan 2016]
Electromagnetic Radiation from QCD Matter: Theory Overview
Chun Shen (McGill U.)🇨🇦
Recent theory developments in electromagnetic radiation from relativistic heavy-ion collisions are reviewed. Electromagnetic observables can serve as a thermometer, a viscometer, and tomographic probes to the collision system. The current status of the "direct photon flow puzzle" is highlighted.
Comments:
8 pages, 4 figures; to appear in the proceedings for the Quark Matter 2015 conference, Kobe, Japan
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1601.02563 [pdf]
NPA(2016)·42 citations
09
[Submitted on 11 Jan 2016]
Jets in d(p)-A Collisions: Color Transparency or Energy Conservation
Michael Kordell II🇺🇸 · Abhijit Majumder🇺🇸
The production of jets, and high momentum hadrons from jets, produced in deuteron ( $d$ )- $A u$ collisions at the relativistic heavy-ion collider (RHIC) and proton ( $p$ )- $P b$ collisions at the large hadron collider (LHC) are studied as a function of centrality, a measure of the impact parameter of the collision. A modified version of the event generator PYTHIA, widely used to simulate $p$ - $p$ collisions, is used in conjunction with a nuclear Monte-Carlo event generator which simulates the locations of the nucleons within a large nucleus. We demonstrate how events with a hard jet may be simulated, in such a way that the parton distribution function of the projectile is frozen during its interaction with the extended nucleus. Using our approach, we demonstrate that the puzzling enhancement seen in peripheral events at RHIC and the LHC, as well as the suppression seen in central events at the LHC are mainly due to mis-binning of central and semi-central events, containing a jet, as peripheral events. This occurs due to the suppression of soft particle production away from the jet, caused by the depletion of energy available in a nucleon of the deuteron (in $d$ - $A u$ at RHIC) or in the proton (in $p$ - $P b$ at LHC), after the production of a hard jet. We conclude that partonic correlations built out of simple energy conservation are mostly responsible for such an effect.
Comments:
15 pages, 22 figures; abstract updated
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1601.02595 [pdf]
PRC(2018)·37 citations

Affiliations

first authorsco-authorsvia INSPIRE