Nuclear Theory·nucl-th

Monday·January 7, 2019

4 papers—3 primary·1 cross-listed

01
[Submitted on 3 Jan 2019]
Non-perturbative Extraction of the Effective Mass in Neutron Matter
Mateusz Buraczynski🇨🇦 · Nawar Ismail🇨🇦 · Alexandros Gezerlis🇨🇦
We carry out non-perturbative calculations of the single-particle excitation spectrum in strongly interacting neutron matter. These are microscopic quantum Monte Carlo computations of many-neutron energies at different densities as well as several distinct excited states. As input, we employ both phenomenological and chiral two- and three-nucleon interactions. We use the single-particle spectrum to extract the effective mass in neutron matter. With a view to systematizing the error involved in this extraction, we carefully assess the impact of finite-size effects on the quasiparticle dispersion relation. We find an effective-mass ratio that drops from 1 as the density is increased. We conclude by connecting our results with the physics of ultracold gases as well as with energy-density functional theories of nuclei and neutron-star matter.
Comments:
5+ pages, 3 figures; v2 corresponds to published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Quantum Gases (cond-mat.quant-gas)
arXiv:
1901.00870 [pdf]
PRL(2019)·22 citations
02
[Submitted on 3 Jan 2019]
Reorientation in newly formed fission fragments
G.F. Bertsch🇺🇸
The strong quadrupolar component of the Coulomb field between newly formed fission fragments can affect the internal energy of the fragments and their angular momentum. Previous estimates of these effects gave contradictory conclusions about their magnitude. Here we calculate them by solving the time-dependent Hamiltonian equation for the daughter $^{100}$ Zr produced in the fission reaction n + $^{235}$ U $\to$ $^{136}$ Te + $^{100}$ Zr. The Hamiltonian was constructed from the projected angular momentum eigenstates of an aligned deformed mean-field configuration. For typical initial conditions, the average angular momentum of the lighter fragment increases by 1.5 - 3 units.
Comments:
To be submitted to Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1901.00928 [pdf]
10 citations
03
[Submitted on 4 Jan 2019]
A brief history of the pion-nucleon coupling constant
Evangelos Matsinos
This work provides a brief history of determinations of the pion-nucleon ( $π N$ ) coupling constant from $π N$ and $N N$ data. From robust analyses of twenty reported values of the charged-pion coupling constant, exhibiting sizeable fluctuation, the result $f_{c}^{2} = 762. 9_{- 6.2}^{+ 6.5} \cdot 1 0^{- 4}$ is obtained. Similar values are extracted for the other two $π N$ coupling constants, $f_{0}^{2}$ and $f_{p}^{2}$ , from fewer data. The average values of the various $π N$ coupling constants, extracted in this work, suggest no splitting, in agreement with the thesis of the Nijmegen group. Additional analysis of the $f_{c}^{2}$ and $f_{0}^{2}$ values, both reported in four studies, turned to be inconclusive: one of these studies suggests that $f_{0} < f_{c}$ , whereas another slightly favours $f_{0} > f_{c}$ ; no significant splitting effects are observed in the other two studies. The analysis of the low-energy $π N$ data with the ETH model indicates significant splitting and, under certain conditions, it implies that $f_{0} > f_{c}$ . Also discussed in the paper are the electromagnetic corrections, which need to be applied to the strong shift and to the total decay width of the ground state of pionic hydrogen in order that estimates for the hadronic $s$ -wave $π N$ scattering lengths be obtained; this is a relevant subject as $f_{c}^{2}$ may be extracted from the isovector scattering length by use of the Goldberger-Miyazawa-Oehme sum rule. Regarding the removal of the electromagnetic effects in the $π N$ system at threshold, my opinion is that Theory must find a way to provide reliable and accurate corrections, matching the level of accuracy of the experimental results.
Comments:
50 pages, 4 figures, 3 tables. Final version: slightly changed database, improved method, improved text, several added references
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1901.01204 [pdf]
20 citations

Affiliations

first authorsco-authorsvia INSPIRE

Non-perturbative Extraction of the Effective Mass in Neutron Matter

Reorientation in newly formed fission fragments

A brief history of the pion-nucleon coupling constant

Affiliations