Nuclear Theory·nucl-th

Wednesday·May 31, 2017

9 papers—5 primary·4 cross-listed

01
Three-nucleon forces and superfluidity in neutron matter
P. Papakonstantinou · J. W. Clark
The existence of superfluidity of the neutron component in the core of a neutron star, associated specifically with triplet $P -$ wave pairing, is currently an open question that is central to interpretation of the observed cooling curves and other neutron-star observables. Ab initio theoretical calculations aimed at resolving this issue face unique challenges in the relevant high-density domain, which reaches beyond the saturation density of symmetrical nuclear matter. These issues include uncertainties in the three-nucleon (3N) interaction and in the effects of strong short-range correlations -- and more generally of in-medium modification of nucleonic self-energies and interactions. A survey of existing solutions to the gap equations in the triplet channel shows that the separate or combined impacts of 3N forces, coupled channels, and mass renormalization range from moderate to strong to devastating, thus motivating a detailed analysis of the competing effects. In the present work we track the effects of the 3N force and in-medium modifications in the representative case of the $^{3} P_{2}$ channel, based on the Argonne V18 two-nucleon (2N) interaction supplemented by 3N interactions of the Urbana IX family. Sensitivity of the results to the input interaction is clearly demonstrated, while consistency issues arise with respect to the simultaneous treatment of 3N forces and in-medium effects. We consider this pilot study as the first step towards a systematic and comprehensive exploration of coupled-channel $^{3} P F_{2}$ pairing using a broad range of 2N and 3N interactions from the current generation of refined semi-phenomenological models and models derived from chiral effective field theory.
nucl-thastro-ph.HEcond-mat.supr-conJ.Low Temp.Phys.(2017)·17 citations
02
The neutron radiation capture process $n + p \to D + γ$ and $^{1} S_{0}$ $n p$ wave function
N.A. Khokhlov
Cross section of the neutron capture reaction $n + p \to d + γ$ at threshold was calculated with different realistic $^{3} S_{1}$ deuteron and $^{1} S_{0}$ $n p$ scattering wave functions stemming from Nijmegen-II, JISP16, Paris, Idaho and Moscow (with forbidden states) potentials. It is found that this reaction with thermal neutrons may be described without a contribution of meson exchange currents.
nucl-th0 citations
03
The potential for $α$ induced nuclear scattering, reaction and decay, and a resonance-pole-decay model with exact explicit analytical solutions
Basudeb Sahu · Swagatika Bhoi
The decay of $α$ particle from a nucleus is viewed as a quantum resonance state of a two-body scattering process of the $α$ +daughter nucleus pair governed by a novel nucleus-nucleus potential in squared Woods-Saxon form. By the application of the rigorous optical model (OM) potential scattering (S-matrix) theory the genuineness of the potential for the system is established by giving good explanation of the elastic scattering and reaction cross sections data of the $α$ +nucleus pair. From the pole position in the complex momentum (k) plane of the S-matrix defined above, the energy and width of the resonance state akin to the decaying state of emission of $α$ particle are extracted and from this width, the result of $α$ -decay half-life is derived to account for the experimental result of half-life in the cases of large number of $α$ -emitters including heavy and super-heavy nuclei. The S-matrix of the full OM calculation above is replaced by an analytical function expressed in terms of exact Schrödinger solutions of a global potential that closely represents the Coulomb-nuclear interaction in the interior and the pure Coulomb wave functions outside, and the resonant poles of this S-matrix in the complex momentum plane are used to give satisfactory results of decay half-lives of $α$ coming out from varieties of nuclei.
nucl-thPRC(2017)·4 citations
04
Generalized Seniority on Deformed Single-Particle Basis
L. Y. Jia
Recently we proposed [62] a fast computing scheme for generalized seniority on spherical single-particle basis. This work redesigns the scheme to make it applicable to deformed single-particle basis. The algorithm is applied to the rare-earth nucleus $_{64}^{158}$ Gd $_{94}$ for intrinsic (body-fixed frame) neutron excitations under the low-momentum {\emph{NN}} interaction $V_{low - k}$ . By allowing as many as four broken pairs, we compute the lowest $300$ intrinsic states of several multipolarity. These states converge well to the exact ones, showing generalized seniority is very effective in truncating the deformed shell model. Under realistic interactions, the picture remains approximately valid that the ground state is a coherent pair condensate, and the pairs gradually break up as excitation energy increases.
nucl-thPRC(2017)·12 citations
05
Initial Angular Momentum and Flow in High Energy Nuclear Collisions
Rainer J. Fries🇺🇸 · Guangyao Chen🇺🇸 · Sidharth Somanathan🇺🇸
We study the transfer of angular momentum in high energy nuclear collisions from the colliding nuclei to the region around midrapidity, using the classical approximation of the Color Glass Condensate (CGC) picture. We find that the angular momentum shortly after the collision (up to times ~ 1/Q_s, where Q_s is the saturation scale) is carried by the "beta-type" flow of the initial classical gluon field, introduced by some of us earlier. beta^i ~ mu_1 nabla^i mu_2 - mu_2 nabla^i mu_1 (i=1,2) describes the rapidity-odd transverse energy flow and emerges from Gauss' Law for gluon fields. Here mu_1 and mu_2 are the averaged color charge fluctuation densities in the two nuclei, respectively. Interestingly, strong coupling calculations using AdS/CFT techniques also find an energy flow term featuring this particular combination of nuclear densities. In classical CGC the order of magnitude of the initial angular momentum per rapidity in the reaction plane, at a time 1/Q_s, is |dL_2/d eta| ~ R_A/Q_s^3 epsilon_0/2 at midrapidity, where R_A is the nuclear radius, and epsilon_0 is the average initial energy density. This result emerges as a cancellation between a vortex of energy flow in the reaction plane aligned with the total angular momentum, and energy shear flow opposed to it. We discuss in detail the process of matching classical Yang-Mills results to fluid dynamics. We will argue that dissipative corrections should not be discarded to ensure that macroscopic conservation laws, e.g. for angular momentum, hold. Viscous fluid dynamics tends to dissipate the shear flow contribution that carries angular momentum in boost-invariant fluid systems. This leads to small residual angular momentum around midrapidity at late times for collisions at high energies.
nucl-thPRC(2018)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE

Three-nucleon forces and superfluidity in neutron matter

The neutron radiation capture process n+p→D+γ and 1S0​ np wave function

The potential for α induced nuclear scattering, reaction and decay, and a resonance-pole-decay model with exact explicit analytical solutions

Generalized Seniority on Deformed Single-Particle Basis

Initial Angular Momentum and Flow in High Energy Nuclear Collisions

Affiliations

The neutron radiation capture process $n + p \to D + γ$ and $^{1} S_{0}$ $n p$ wave function

The potential for $α$ induced nuclear scattering, reaction and decay, and a resonance-pole-decay model with exact explicit analytical solutions