Nuclear Theory·nucl-th

Monday·May 9, 2022

7 papers—3 primary·4 cross-listed

01
[Submitted on 5 May 2022]
What has been learnt from the analysis of the low-energy pion-nucleon data during the past three decades?
Evangelos Matsinos🇨🇭
Over twenty-five years ago, two analyses of the pion-nucleon ( $π N$ ) data at low energy (i.e., for pion laboratory kinetic energy $T \leq 100$ MeV) reported on the departure of the extracted scattering amplitudes, corresponding to the two elastic-scattering reactions $π^{\pm} p \to π^{\pm} p$ and to the $π^{-} p$ charge-exchange reaction $π^{-} p \to π^{0} n$ , from the triangle identity, which these amplitudes fulfil if the isospin invariance holds in the hadronic part of the $π N$ interaction. This discrepancy indicates that \emph{at least one} of the following assumptions is not valid: first, that the absolute normalisation of the bulk of the low-energy $π N$ datasets is correct; second, that any residual contributions to the corrections, which aim at the removal of the effects of electromagnetic (EM) origin from the measurements, are not significant; and third, that the isospin invariance holds in the hadronic part of the $π N$ interaction. In view of the incompatibility of the results of the various schemes of removal of the so-called trivial EM effects at the $π N$ threshold ( $T = 0$ MeV), the likelihood of residual effects of EM origin in the extracted $π N$ scattering amplitudes (from the data in the scattering region, i.e., above the $π N$ threshold) must be reassessed. This work emphasises the importance of the development of a unified scheme for the determination of reliable EM corrections, \emph{applicable at the $π N$ threshold and in the scattering region}, in providing a resolution to the established discrepancy at low energy.
Comments:
60 pages, 11 figures, 3 tables. Changes to the first version: minor occasional modifications to improve readability; correction of one mistake on p. 44 (of the first version), two lines before Eq. (17); addition of three references: [34], [63], and [65] (updated version). No numerical values have been changed: the tables and the figures are identical to those of the first version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2205.02899 [pdf]
3 citations
02
[Submitted on 6 May 2022]
Resonance nucleon scattering amplitude in the photonuclear reaction
Swapan Das🇮🇳
The cross section of the photonuclear reaction in the nucleon-resonance region is calculated to search the resonance-nucleon scattering amplitude in the nucleus. It is assumed that the resonance $R$ is produced and decayed in the elementary photon-nucleon $(γ N)$ reaction in the nucleus as $γ N \to R \to γ N$ . The resonance interacts with the nucleons while propagating through the nucleus. Therefore, the calculated photonuclear reaction cross section is compared with the data to extract the resonance-nucleon scattering parameters in the nucleus.
Comments:
17 pages, 6 Figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2205.03025 [pdf]
NPA(2023)·0 citations
03
[Submitted on 6 May 2022]
Equations of state for hot neutron stars -- II. The role of exotic particle degrees of freedom
Adriana R. Raduta🇷🇴
Explosive astrophysical systems - such as supernovae or compact star binary mergers - provide conditions where exotic degrees of freedom can be populated. Within the covariant density functional theory of nuclear matter we build several general purpose equations of state which, in addition to the baryonic octet, account for $Δ (1232)$ resonance states. The thermodynamic stability of $Δ$ -admixed nuclear matter is investigated in the limiting case of vanishing temperature for charge fractions $Y_{Q} = 0.01$ and $Y_{Q} = 0.5$ and wide ranges of the coupling constants to the scalar and vector mesonic fields. General purpose equation of state models with exotica presently available on the \textsc{CompOSE} database are further reviewed; for a selection of them we then investigate thermal properties for thermodynamic conditions relevant for core-collapse supernovae and binary neutron star mergers. Modifications induced by hyperons, $Δ (1232)$ , $K^{-}$ , pions and quarks are discussed.
Comments:
26 pages; 22 figures; contribution to the EPJ A Topical Issue "CompOSE: a repository for Neutron Star Equations of State and Transport Properties"
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2205.03177 [pdf]
EPJA(2022)·50 citations

Affiliations

first authorsco-authorsvia INSPIRE

What has been learnt from the analysis of the low-energy pion-nucleon data during the past three decades?

Resonance nucleon scattering amplitude in the photonuclear reaction

Equations of state for hot neutron stars -- II. The role of exotic particle degrees of freedom

Affiliations