Nuclear Theory·nucl-th

Tuesday·December 13, 2016

10 papers—6 primary·4 cross-listed

01
[Submitted on 10 Dec 2016]
Chaos and regularity in the doubly magic nucleus 208Pb
B. Dietz · A. Heusler · K. H. Maier · A. Richter · B. A. Brown
High resolution experiments have recently lead to a complete identification (energy, spin, and parity) of 151 nuclear levels up to an excitation Energy of Ex= 6.20 MeV in 208Pb. We present a thorough study of the fluctuation properties in the energy spectra of the unprecedented set of nuclear bound states. In a first approach we grouped states with the same spin and parity into 14 subspectra, analyzed standard statistical measures for short- and long-range correlations and then computed their ensemble average. Their comparison with a random matrix ensemble which interpolates between Poisson statistics expected for regular systems and the Gaussian Orthogonal Ensemble (GOE) predicted for chaotic systems shows that the data are well described by the GOE. In a second approach, following an idea of Rosenzweig and Porter we considered the complete spectrum composed of the independent subspectra. We analyzed their fluctuation properties using the method of Bayesian inference involving a quantitative measure, called the chaoticity parameter f, which also interpolates between Poisson (f=0) and GOE statistics (f=1). It turns out to be f~0.9. This is so far the closest agreement with GOE observed in spectra of bound states in a nucleus. The same analysis has also been performed with spectra computed on the basis of shell model calculations with different interactions (SDI, KB, M3Y). While the simple SDI exhibits features typical for nuclear many-body systems with regular dynamics, the other, more realistic interactions yield chaoticity parameters f close to the experimental values.
Subjects:
Nuclear Theory (nucl-th); nlin.CD (nlin.CD); Nuclear Experiment (nucl-ex)
arXiv:
1612.03260 [pdf]
PRL(2017)·26 citations
02
[Submitted on 10 Dec 2016]
Effect of meson cloud on the jet nuclear modification factor in $p A$ collisions
B.G. Zakharov🇷🇺
We study the effect of the nucleon meson cloud on centrality dependence of the jet nuclear modification factor $R_{p A}$ . We find that the meson-baryon Fock components may lead to a noticeable deviation of $R_{p A}$ from unity. Our results for $R_{p A}$ show the same tendency as that observed by ATLAS in $p + P b$ collisions at $s = 5.02$ 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.
Comments:
5 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.03337 [pdf]
JETP Lett.(2017)·1 citation
03
[Submitted on 12 Dec 2016]
Neutrino Processes with Hot Nuclei in Supernovae
Alan A. Dzhioev🇷🇺 · A. I. Vdovin🇷🇺
In this paper, we calculate cross sections for charged-current neutrino-nucleus processes occuring under presupernova conditions. To treat thermal effects we extend self-consistent Skyrme-QRPA calculations to finite temperature by using the formalism of thermo field dynamics. The numerical results are presented for the sample nuclei, $^{56}$ Fe and $^{82}$ Ge
Comments:
Contribution to the Proceedings of the 2016 Zakopane Conference on Nuclear Physics, Zakopane, Poland, August 28 - September 4, 2016
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1612.03611 [pdf]
Acta Phys.Polon.B(2017)·2 citations
04
[Submitted on 12 Dec 2016]
Lambda-nuclear interactions and hyperon puzzle in neutron stars
J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪 · N. Kaiser🇩🇪 · W. Weise🇩🇪
Brueckner theory is used to investigate the in-medium properties of a $Λ$ -hyperon in nuclear and neutron matter, based on hyperon-nucleon interactions derived within SU(3) chiral effective field theory (EFT). It is shown that the resulting $Λ$ single-particle potential $U_{Λ} (p_{Λ} = 0, ρ)$ becomes strongly repulsive for densities $ρ$ of two-to-three times that of normal nuclear matter. Adding a density-dependent effective $Λ N$ -interaction constructed from chiral $Λ N N$ three-body forces increases the repulsion further. Consequences of these findings for neutron stars are discussed. It is argued that for hyperon-nuclear interactions with properties such as those deduced from the SU(3) EFT potentials, the onset for hyperon formation in the core of neutron stars is expected to be shifted to extremely high baryon density, thus potentially resolving the so-called hyperon puzzle.
Comments:
6 pages, two figures; longer discussion about uncertainties added
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1612.03758 [pdf]
EPJA(2017)·81 citations
05
[Submitted on 12 Dec 2016]
Interaction between antiprotonic helium ion and He atom: Potential Energy Surface
S. N. Yudin (1) · I. V. Bodrenko (2) · G. Ya. Korenman (1) ((1) Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia (2) Department of Physics, University of Cagliari, Cagliari, Italy)
Potential Energy Surface for the ( $p ˉ - He^{2 +} - He$ ) system is calculated in the framework of the restricted (singlet spin state) Hartree-Fock method with subsequent account of the electronic correlations within the second order perturbation method (MP2). The geometry of heavy particles is described in variables of distance $r$ from nucleus $a$ to antiproton, distance $R$ from the center of mass of the $(p ˉ - a)$ pair to $He$ atom containing nucleus $b$ , and an angle $θ$ between $r$ and $R$ . The potential $V (R, r, cos θ)$ of the interaction between $He$ atom and a $p ˉ - a$ subsystem involves a total energy of two electrons in the field of three heavy particles and Coulomb interactions of the $b$ nucleus with antiproton and the $a$ nucleus. The expansion of this potential in terms of Legendre polynomials $P_{k} (cos θ)$ is obtained. Matrices of the multipole terms $V^{k} (r, R)$ ( $k = 0, 1, 2$ ) are obtained in the basis of antiprotonic helium ion states. The results are compared with the model potential that was used earlier in the calculations of collisional Stark transitions of $(p ˉ He^{2 +})$ ion.Total cross sections of collisional Stark transitions obtained with the PES potentials exceed the model results by 15 - 20\% at $E \leq 12$ K.
Comments:
11 pages, 18 fugures
Subjects:
Nuclear Theory (nucl-th); physics.chem-ph (physics.chem-ph); Quantum Physics (quant-ph)
arXiv:
1612.03874 [pdf]
1 citation
06
[Submitted on 12 Dec 2016]
Impact of resonance decays on critical point signals in net-proton fluctuations
Marcus Bluhm (North Carolina State U.)🇺🇸 · Marlene Nahrgang (SUBATECH, Nantes & Duke U.)🇫🇷 · Steffen A. Bass (Duke U.)🇺🇸 · Thomas Schaefer (North Carolina State U.)🇺🇸
The non-monotonic beam energy dependence of the higher cumulants of net-proton fluctuations is a widely studied signature of the conjectured presence of a critical point in the QCD phase diagram. In this work we study the effect of resonance decays on critical fluctuations. We show that resonance effects reduce the signatures of critical fluctuations, but that for reasonable parameter choices critical effects in the net-proton cumulants survive. The relative role of resonance decays has a weak dependence on the order of the cumulants studied with a slightly stronger suppression of critical effects for higher-order cumulants.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1612.03889 [pdf]
EPJC(2017)·34 citations

Affiliations

first authorsco-authorsvia INSPIRE

Chaos and regularity in the doubly magic nucleus 208Pb

Effect of meson cloud on the jet nuclear modification factor in pA collisions

Neutrino Processes with Hot Nuclei in Supernovae

Lambda-nuclear interactions and hyperon puzzle in neutron stars

Interaction between antiprotonic helium ion and He atom: Potential Energy Surface

Impact of resonance decays on critical point signals in net-proton fluctuations

Affiliations

Effect of meson cloud on the jet nuclear modification factor in $p A$ collisions