Nuclear Theory·nucl-th

Friday·August 25, 2017

9 papers—6 primary·3 cross-listed

01
[Submitted on 23 Aug 2017]
Determination of the $^{36}$ Mg( $n, γ$ ) $^{37}$ Mg reaction rate from Coulomb dissociation of $^{37}$ Mg
Sharma Shubhchintak🇺🇸 · R. Chatterjee · R. Shyam🇮🇳
We use the Coulomb dissociation (CD) method to calculate the rate of the $^{36}$ Mg( $n, γ$ ) $^{37}$ Mg radiative capture reaction. The CD cross sections of the $^{37}$ Mg nucleus on a $^{208}$ Pb target at the beam energy of 244 MeV/nucleon, for which new experimental data have recently become available, were calculated within the framework of a finite range distorted wave Born approximation theory that is extended to include the projectile deformation effects. Invoking the principle of detailed balance, these cross sections are used to determine the excitation function and subsequently the rate of the $^{36}$ Mg( $n, γ$ ) $^{37}$ Mg reaction. We compare these rates to those of the $^{36}$ Mg( $α, n$ ) $^{39}$ Si reaction calculated within a Hauser-Feshbach model. We find that for $T_{9}$ as large as up to 1.0 (in units of 10 $^{9}$ K) the $^{36}$ Mg( $n, γ$ ) $^{37}$ Mg reaction is much faster than the $^{36}$ Mg( $α, n$ ) $^{39}$ Si one. The inclusion of the effects of $^{37}$ Mg projectile deformation in the breakup calculations, enhances the ( $n, γ$ ) reaction rate even further. Therefore, it is highly unlikely that the $(n, γ)$ $β$ -decay $r$ -process flow will be broken at the $^{36}$ Mg isotope by the $α$ -process.
Comments:
Published in Physical Review C
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1708.07152 [pdf]
PRC(2017)·18 citations
02
[Submitted on 23 Aug 2017]
Enhancement of the Triple Alpha Rate in a Hot Dense Medium
Mary Beard · Sam M. Austin · Richard Cyburt
In a sufficiently hot and dense astrophysical environment the rate of the triple-alpha (3alpha) reaction can increase greatly over the value appropriate for helium burning stars owing to hadronically induced de-excitation of the Hoyle state. In this paper we use a statistical model to evaluate the enhancement as a function of temperature and density. For a density of $1 0^{6} g m c m^{- 3}$ enhancements can exceed a factor of one-hundred. In high temperature/density situations, the enhanced 3alpha rate is a better estimate of this rate and should be used in these circumstances. We then examine the effect of these enhancements on production of $^{12}$ C in the neutrino wind following a supernova explosion and in an x-ray burster.
Comments:
Accepted for publication in Physical Review Leters
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1708.07204 [pdf]
PRL(2017)·22 citations
03
[Submitted on 23 Aug 2017]
Role of small-norm components in extended random-phase approximation
Mitsuru Tohyama
The role of the small-norm amplitudes in extended RPA theories such as the particle-particle and hole-hole components of one-body amplitudes and the two-body amplitudes other than two particle - two holes components are investigated for the one-dimensional Hubbard model using an extended RPA derived from the time-dependent density-matrix theory. It is found that these amplitudes cannot be neglected in strongly interacting regions where the effects of ground-state correlations are significant.
Comments:
11 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1708.07219 [pdf]
PTEP(2017)·5 citations
04
[Submitted on 24 Aug 2017]
Chiral geometry in symmetry restored states: Chiral doublet bands in 128Cs
F.Q. Chen · Q.B. Chen · Y.A. Luo · J. Meng · S.Q. Zhang
The pairing-plus-quadrupole Hamiltonian is diagonalized in a symmetry restored basis, i.e., the triaxial quasiparticle-states with angular momentum and particle number projections, and applied for chiral doublet bands in 128Cs. The observed energy spectra and electromagnetic transition probabilities are reproduced well without introducing any parameter. The orientation of the angular momentum in the intrinsic frame is investigated by the distributions of its components on the three principle axes as well as those of its tilted angles. The evolution of the chirality with spin is illustrated and the chiral geometry is demonstrated in the angular momentum projected model for the first time.
Comments:
12 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1708.07282 [pdf]
PRC(2017)·68 citations
05
[Submitted on 24 Aug 2017]
Nuclear symmetry energy with mesonic cross-couplings in the effective chiral model
Tuhin Malik · Kinjal Banerjee · T. K. Jha · B. K. Agrawal
The effective chiral model is extended by introducing the contributions from the cross-couplings between isovector and isoscalar mesons. These cross-couplings are found to be instrumental in improving the density content of the nuclear symmetry energy. The nuclear symmetry energy as well as its slope and curvature parameters at the saturation density are in harmony with those deduced from a diverse set of experimental data. The equation of state for pure neutron matter at sub-saturation densities is also in accordance with the ones obtained from different microscopic models. The maximum mass of neutron star is consistent with the measurement and the radius at the canonical mass of the neutron star is within the empirical bounds.
Comments:
8 pages, 5 figures, Accepted in Physical Review C as a regular article
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1708.07291 [pdf]
PRC(2017)·23 citations
06
[Submitted on 24 Aug 2017]
Improved modeling of photon observables with FREYA
R. Vogt · J. Randrup
The event-by-event fission model FREYA has been improved, in particular to address deficiencies in the calculation of photon observables. We discuss the improvements that have been made and introduce several new variables, some detector dependent, that affect the photon observables. We show the sensitivity of FREYA to these variables. We then compare the results to the available photon data from spontaneous and thermal neutron-induced fission.
Comments:
25 pages, 31 figures, version as accepted in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1708.07312 [pdf]
PRC(2017)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

Determination of the 36Mg(n,γ)37Mg reaction rate from Coulomb dissociation of 37Mg

Enhancement of the Triple Alpha Rate in a Hot Dense Medium

Role of small-norm components in extended random-phase approximation

Chiral geometry in symmetry restored states: Chiral doublet bands in 128Cs

Nuclear symmetry energy with mesonic cross-couplings in the effective chiral model

Improved modeling of photon observables with FREYA

Affiliations

Determination of the $^{36}$ Mg( $n, γ$ ) $^{37}$ Mg reaction rate from Coulomb dissociation of $^{37}$ Mg