Nuclear Theory·nucl-th

Thursday·December 7, 2017

8 papers—6 primary·2 cross-listed

01
[Submitted on 5 Dec 2017]
Isotopic dependence of the fragments' internal temperatures observed in multifragment emission
S.R. Souza · R. Donangelo
The internal temperatures of fragments produced by an excited nuclear source are investigated using the microcanonical version of the Statistical Multifragmentation Model, with discrete energy. We focus on the fragments' properties at the breakup stage, before they have time to deexcite by particle emission. Since the adopted model provides the excitation energy distribution of these primordial fragments, it allows one to calculate the temperatures of different isotope families and infer on the sensitivity to their isospin composition. It is found that, due to the functional form of the nuclear density of states and the excitation energy distribution of the fragments, proton rich isotopes are hotter than neutron rich ones. This property has been taken to be an indication of earlier emission of the former from a source that cools down as it expands and emits fragments. Although this scenario is incompatible with the prompt breakup of a thermally equilibrated source, our results reveal that the latter framework also provides the same qualitative features just mentioned. Therefore they suggest that this property cannot be taken as evidence for non-equilibrium emission. We also found that this sensitivity to the isotopic composition of the fragments depends on the isospin composition of the source, and that it is weakened as the excitation energy of the source increases.
Comments:
5 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1712.01910 [pdf]
PRC(2018)·2 citations
02
[Submitted on 5 Dec 2017]
On the Relativistic Separable Functions for the Breakup Reactions
Serge G. Bondarenko · Valery V. Burov · Elena P. Rogochaya (JINR)
In the paper the so-called modified Yamaguchi function for the Bethe-Salpeter equation with a separable kernel is discussed. The type of the functions is defined by the analytic stucture of the hadron current with breakup - the reactions with interacting nucleon-nucleon pair in the final state (electro-, photo-, and nucleon-disintegration of the deuteron).
Comments:
4 pages, 2 figures, to be published in EPJ WoC
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.01966 [pdf]
EPJ Web Conf.(2018)·0 citations
03
[Submitted on 6 Dec 2017]
Squeezed back-to-back correlation of $\bqD^{0} \bqD ˉ^{0}$ in relativistic heavy-ion collisions
Ai-Geng Yang🇨🇳 · Yong Zhang🇨🇳 · Luan Cheng🇨🇳 · Hao Sun🇨🇳 · Wei-Ning Zhang🇨🇳
We investigate the squeezed back-to-back correlation (BBC) of $D^{0} D ˉ^{0}$ in relativistic heavy-ion collisions, using the in-medium mass modification calculated with a self-energy in hot pion gas and the source space-time distributions provided by the viscous hydrodynamic code VISH2+1. It is found that the BBC of $D^{0} D ˉ^{0}$ is significant in peripheral Au+Au collisions at the RHIC energy. A possible way to detect the BBC in experiment is presented.
Comments:
4 pages, 5 figures, will be published in Chin. Phys. Lett
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.02004 [pdf]
Chin.Phys.Lett.(2018)·9 citations
04
[Submitted on 6 Dec 2017]
Effects of ground-state correlations on dipole and quadrupole excitations of $^{40}$ Ca and $^{48}$ Ca
Mitsuru Tohyama
The effects of ground-state correlations on the dipole and quadrupole excitations are studied for $^{40}$ Ca and $^{48}$ Ca using the extended random phase approximation (ERPA) derived from the time-dependent density-matrix theory. Large effects of the ground-state correlations are found in the fragmentation of the giant quadrupole resonance in $^{40}$ Ca and in the low-lying dipole strength in $^{48}$ Ca. It is discussed that the former is due to a mixing of different configurations in the ground state and the latter is from the partial occupation of the neutron single-particle states. The dipole and quadrupole strength distributions below 10 MeV calculated in ERPA are in qualitatively agreement with experiment.
Comments:
8 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.02006 [pdf]
PTEP(2018)·4 citations
05
[Submitted on 6 Dec 2017]
The density- and isospin- dependent $Δ$ -formation cross section and its decay width
Qingfeng Li🇨🇳 · Zhuxia Li🇨🇳
The energy-, density-, and isospin-dependent $Δ$ -formation cross section $σ_{N π \to Δ}^{*}$ and $Δ$ -decay width are calculated based on the relativistic BUU approach in which the effective mass splitting of nucleon and $Δ$ baryons in isospin-asymmetric matter is considered by the inclusion of the $δ$ meson exchange in the effective Lagrangian density. With the density-dependent couplings for baryons of F. Hofmann et al., the $σ_{N π \to Δ}^{*}$ is decreased (increased) moderately with increasing density with (without) the consideration of the density dependent pion effective mass. Meanwhile, if the invariant mass of the system is not far from the $Δ$ pole mass, the $Δ$ -decay width is also weakly dependent on density. The mass splitting effect of differently charged nucleon and $Δ$ baryons on $σ_{N π \to Δ}^{*}$ are found to be more obvious than that of pion mesons but much weaker than the mass splitting in the hard $Δ$ production channel $N N \to N Δ$ . Further, the largest mass-splitting influence is seen in the $π^{-} p \to Δ^{0}$ and $π^{+} n \to Δ^{+}$ channels but not in the production of $Δ^{-}$ and $Δ^{++}$ isobars.
Comments:
11 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1712.02062 [pdf]
SCPMA(2019)·19 citations
06
[Submitted on 5 Dec 2017]
XSgen: A Cross Section Generation Methodology for Fuel Cycle Simulation
Robert Flanagan · Anthony Scopatz
This work investigates a method for generating medium fidelity reactor model cross sections. The methodology used here couples a neutron transport code with a depletion calculator. Together the two can be used to generate time dependent group cross sections for medium fidelity reactor models in fuel cycle simulation. This work analyzes XSgen, a software that performs the functions mentioned above. Addtionally, it is shown that XSgen is capable of creating datasets for a medium fidelity reactor model known as Bright-lite. The results of this work show that XSgen produces datasets that match NEA benchmarks for both uranium based LWR, and MOX reactors.
Comments:
Preprint
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1712.02241 [pdf]
0 citations
07
[Submitted on 6 Dec 2017] (cross-list from hep-ph)
Spectral Functions from the Functional Renormalization Group
Jochen Wambach🇮🇹 · Christopher Jung🇩🇪 · Fabian Rennecke🇺🇸 · Ralf-Arno Tripolt🇩🇪 · Lorenz von Smekal🇩🇪
We present results for in-medium spectral functions obtained within the Functional Renormalization Group framework. The analytic continuation from imaginary to real time is performed in a well-defined way on the level of the flow equations. Based on this recently developed method, results for the sigma and the pion spectral function for the quark-meson model are shown at finite temperature, finite quark-chemical potential and finite spatial momentum. It is shown how these spectral function become degenreate at high temperatures due to the restoration of chiral symmetry. In addition, results for vector- and axial-vector meson spectral functions are shown using a gauged linear sigma model with quarks. The degeneration of the $ρ$ and the $a_{1}$ spectral function as well as the behavior of their pole masses is discussed.
Comments:
CPOD 2017 Proceedings
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1712.02093 [pdf]
PoS(2018)·2 citations
08
[Submitted on 6 Dec 2017] (cross-list from hep-ph)
Amplitude analysis of the anomalous decay $η^{'} \to π^{+} π^{-} γ$
Ling-Yun Dai🇨🇳 · Xian-Wei Kang🇹🇼 · Ulf-G. Meißner🇩🇪 · Xin-Ying Song🇩🇪 · De-Liang Yao🇪🇸
In this paper we perform an amplitude analysis of $η^{'} \to π^{+} π^{-} γ$ and confront it with the latest BESIII data. Based on the final-state interaction theorem, we represent the amplitude in terms of an Omnés function multiplied by a form factor that corresponds to the contributions from left-hand cuts and right-hand cuts in the inelastic channels. We also take into account the isospin violation effect induced by $ρ - ω$ mixing. Our results show that the anomaly contribution is mandatory in order to explain the data. Its contribution to the decay width of $Γ (η^{'} \to π π γ)$ is larger than that induced by isospin violation. Finally we extract the pole positions of the $ρ$ and $ω$ as well as their corresponding residues.
Comments:
12 pages, 5 figures, typos corrected
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1712.02119 [pdf]
PRD(2018)·25 citations

Affiliations

first authorsco-authorsvia INSPIRE