Nuclear Theory·nucl-th

Thursday·April 30, 2015

8 papers—4 primary·4 cross-listed

01
[Submitted on 28 Apr 2015]
Particle-hole nature of the light high-spin toroidal isomers
A. Staszczak · Cheuk-Yin Wong
Nuclei under non-collective rotation with a large angular momentum above some threshold can assume a toroidal shape. In our previous work, we showed by using cranked Skyrme-Hartree-Fock approach that even-even, N=Z, high-K, toroidal isomeric states may have general occurrences for light nuclei with 28<=A<=52. We present here some additional results and systematics on the particle-hole nature of these high-spin toroidal isomers.
Comments:
7 pages, 5 figures, presented at the Zakopane Conference on Nuclear Physics 'Extremes of the Nuclear Landscape', Zakopane, Poland, August 31 - September 7, 2014
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.07646 [pdf]
Acta Phys.Polon.B(2015)·10 citations
02
[Submitted on 29 Apr 2015]
Shape transition in the even-even Cerium isotopes
B. Mohammed-Azizi · A. Helmaoui · D. E. Medjadi
The deformation energy of the even-even nuclei of the Cerium isotopic chain is investigated by means of the Macroscopic-Microscopic method with a semi-classical shell correction. We consider axially symmetric shapes. Binding energy and two neutron separation energy are also evaluated. For the sake of clarity several important details of the calculations are also given. It turns out that all these nuclei have prolate equilibrium shape. The regions of maximum deformation are obtained around N=64 and N=102. There is no critical-point of quantum phase transition in this isotopic chain.
Comments:
14 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.07726 [pdf]
Progress in Physics, vol. 11 (2015), issu…·0 citations
03
[Submitted on 29 Apr 2015]
Resonant states of neutron-rich $Λ$ hypernucleus $_{Λ}^{7}$ He
E. Hiyama🇯🇵 · M. Isaka🇯🇵 · M. Kamimura🇯🇵 · T. Myo🇯🇵 · T. Motoba🇯🇵
The structure of neutron-rich $Λ$ hypernucleus, $_{Λ}^{7}$ He is studied within the framework of an $α + Λ + n + n$ four-body cluster model. We predict second $3/ 2^{+}$ and $5/ 2^{+}$ states, corresponding to a $0 s$ $Λ$ coupled to the second $2^{+}$ state of $^{6}$ He, as narrow resonant states with widths $Γ \sim 1$ MeV to be at 0.03 MeV and 0.07 MeV respect to the $α + Λ + n + n$ threshold. From an estimation of the differential cross section for the $^{7} Li (γ, K^{+})_{Λ}^{7}$ He reaction, there is a possibility to observe these state at JLab in the future. We also calculate the second $2^{+}$ state of $^{6}$ He as resonant state within the framework of an $α + n + n$ three-body cluster model. Our result is $2.81$ MeV with $Γ =$ 4.63 MeV with respect to the $α + n + n$ threshold. This energy position is $\sim 1$ MeV higher, and with a much broader decay width, than the recent SPIRAL data. It is suggested that an experiment at JLab to search for the second $3/ 2^{+}$ and $5/ 2^{+}$ states of $_{Λ}^{7}$ He would provide an opportunity to confirm the second $2^{+}$ state of the core nucleus $^{6}$ He.
Comments:
6 pages, 4 figures,published in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.07735 [pdf]
PRC(2015)·29 citations
04
[Submitted on 29 Apr 2015]
Low-energy theorems for nucleon-nucleon scattering at unphysical pion masses
V. Baru🇩🇪 · E. Epelbaum🇩🇪 · A. A. Filin🇩🇪 · J. Gegelia🇩🇪
The longest-range part of the nuclear force due to the one-pion exchange governs the energy dependence of the scattering amplitude in the near-threshold region and imposes correlations between the coefficients in the effective range expansion. These correlations may be regarded as low-energy theorems and are known to hold to a high accuracy in the neutron-proton 3S1 partial wave. We generalize the low-energy theorems to the case of unphysical pion masses and provide results for the correlations between the coefficients in the effective range expansion in this partial wave for pion masses up to Mpi ~ 400 MeV. We discuss the implications of our findings for the available and upcoming lattice-QCD simulations of two-nucleon observables.
Comments:
17 pages, 7 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1504.07852 [pdf]
PRC(2015)·41 citations
05
[Submitted on 28 Apr 2015] (cross-list from astro-ph.SR)
Neutrino-driven explosion of a 20 solar-mass star in three dimensions enabled by strange-quark contributions to neutrino-nucleon scattering
Tobias Melson (1,2)🇩🇪 · Hans-Thomas Janka (1)🇩🇪 · Robert Bollig (1,2)🇩🇪 · Florian Hanke (1,2)🇩🇪 · Andreas Marek (3)🇩🇪 · Bernhard Mueller (4) ((1) MPI Astrophysics, Garching, (2) Physik Dept., TUM, Garching, (3) RZG Garching, (4) Monash University, Victoria)🇦🇺
Interactions with neutrons and protons play a crucial role for the neutrino opacity of matter in the supernova core. Their current implementation in many simulation codes, however, is rather schematic and ignores not only modifications for the correlated nuclear medium of the nascent neutron star, but also free-space corrections from nucleon recoil, weak magnetism or strange quarks, which can easily add up to changes of several 10% for neutrino energies in the spectral peak. In the Garching supernova simulations with the Prometheus-Vertex code, such sophistications have been included for a long time except for the strange-quark contributions to the nucleon spin, which affect neutral-current neutrino scattering. We demonstrate on the basis of a 20 M_sun progenitor star that a moderate strangeness-dependent contribution of g_a^s = -0.2 to the axial-vector coupling constant g_a = 1.26 can turn an unsuccessful three-dimensional (3D) model into a successful explosion. Such a modification is in the direction of current experimental results and reduces the neutral-current scattering opacity of neutrons, which dominate in the medium around and above the neutrinosphere. This leads to increased luminosities and mean energies of all neutrino species and strengthens the neutrino-energy deposition in the heating layer. Higher nonradial kinetic energy in the gain layer signals enhanced buoyancy activity that enables the onset of the explosion at ~300 ms after bounce, in contrast to the model with vanishing strangeness contributions to neutrino-nucleon scattering. Our results demonstrate the close proximity to explosion of the previously published, unsuccessful 3D models of the Garching group.
Comments:
8 pages, 5 figures; minor revisions, accepted by ApJL
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1504.07631 [pdf]
ApJL(2015)·229 citations
06
[Submitted on 29 Apr 2015] (cross-list from hep-ph)
Temperature dependence of meson screening masses; a comparison of effective model with lattice QCD
Masahiro Ishii🇯🇵 · Takahiro Sasaki🇯🇵 · Kouji Kashiwa🇯🇵 · Hiroaki Kouno🇯🇵 · Masanobu Yahiro🇯🇵
Temperature dependence of pion and sigma-meson screening masses is evaluated by the Polyakov-loop extended Nambu--Jona-Lasinio model with the entanglement vertex (EPNJL model). We propose a practical way of calculating meson screening masses in the NJL-type effective models. The method based on the Pauli-Villars regularization solves the well-known difficulty that the evaluation of screening masses is not easy in the NJL-type effective models. The method is applied to analyze temperature dependence of pion screening masses calculated with state-of-the-art lattice simulations with success in reproducing the lattice QCD results. We predict the temperature dependence of pole mass by using EPNJL model.
Comments:
7 pages, 3 figures, Presented at The 32nd International Symposium on Lattice Field Theory, Lattice2014
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1504.07706 [pdf]
PoS(2014)·0 citations
07
[Submitted on 29 Apr 2015] (cross-list from hep-ph)
The $ψ$ (3770) resonance and its production in $p ˉ p \to D D ˉ$
J. Haidenbauer🇩🇪 · G. Krein🇧🇷
The production of a $D D ˉ$ meson-pair in antiproton-proton ( $p ˉ p$ ) annihilation close to the production threshold is investigated, with special emphasis on the role played by the $ψ$ (3770) resonance. The study is performed in a meson-baryon model where the elementary charm production process is described by baryon exchange. Effects of the interactions in the initial and final states are taken into account rigorously, where the latter involves also those due to the $ψ$ (3770). The predictions for the $D D ˉ$ production cross section are in the range of 30 -- 250 nb, the contribution from the $ψ$ (3770) resonance itself amounts to roughly 20 -- 80 nb.
Comments:
6 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1504.07909 [pdf]
PRD(2015)·13 citations
08
[Submitted on 29 Apr 2015] (cross-list from hep-ph)
Higher order anisotropies in hydrodynamics
M. Csanad🇭🇺 · A. Szabo🇭🇺 · S. Lokos🇭🇺 · A. Bagoly🇭🇺
In the last years it has been revealed that if measuring relative to higher order event planes $Ψ_{n}$ , higher order flow coefficients $v_{n}$ for $n > 2$ can be measured. It also turned out that Bose-Einstein (HBT) correlation radii also show 3rd order oscillations if measured versus the third order event plane $Ψ_{3}$ . In this paper we investigate how these observables can be described via analytic hydro solutions and hydro parameterizations. We also investigate the time evolution of asymmetry coefficients and the mixing of velocity field asymmetries and density asymmetries.
Comments:
8 pages, 6 figures. Presented at the X Workshop on Particle Correlations and Femtoscopy (WPCF 2014), Gyongyos, Hungary
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1504.07932 [pdf]
JCEGI 4(4) pp 46-52 (2016)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE