Nuclear Theory·nucl-th

Thursday·August 17, 2017

9 papers—3 primary·6 cross-listed

01
[Submitted on 16 Aug 2017]
Charge symmetry breaking in light $Λ$ hypernuclei
Avraham Gal🇮🇱 · Daniel Gazda🇸🇪
Charge symmetry breaking (CSB) is particularly strong in the A=4 mirror hypernuclei $_{Λ}^{4}$ H-- $_{Λ}^{4}$ He. Recent four-body no-core shell model calculations that confront this CSB by introducing $Λ$ - $Σ^{0}$ mixing to leading-order chiral effective field theory hyperon-nucleon potentials are reviewed, and a shell-model approach to CSB in p-shell $Λ$ hypernuclei is outlined.
Comments:
presented by A. Gal at the 12th International Seminar on Nuclear Physics, Sant'Angelo d'Ischia, May 15-19 2017; prepared for J. Phys. Conf.; v2 -- slightly expanded version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1708.04791 [pdf]
J.Phys.Conf.Ser.(2018)·7 citations
02
[Submitted on 15 Aug 2017]
Mass number and excitation energy dependence of the $Θ_{e f f} / Θ_{r i g}$ parameter of the spin cut-off factor in the formation of an isomeric pair
S. Sudár (1) · S. M. Qaim (2) ((1) Institute of Experimental Physics, University of Debrecen, Hungary, (2) Institut für Neurowissenschaften und Medizin, INM-5: Nuklearchemie, Forschungszentrum Jülich GmbH, Germany)
The $Θ_{e f f} / Θ_{r i g}$ parameter of the spin distribution of the level density was determined for 61 nuclei covering the mass range of 44 to 200. The experimental isomeric cross-section ratios for 25 isomeric pairs were compared with the model calculation to find the best fit to the experimental data. The model calculations were carried out with the TALYS code using the BSFG model for the level density. The reduced $χ^{2}$ values were calculated to describe the deviation of the experimental data from the model calculation. An $η_{d}$ was introduced calculating the $Θ_{e f f} / Θ_{r i g}$ value from the low energy discrete levels of the nucleus. The $η / η_{d}$ values seem to be independent of the mass number, their average value near to one. The $η / η_{d}$ values also seem to be independent of the average excitation energy in the continuum, indicating that $η$ is independent of the excitation energy. The mass number and (N-Z) dependence of the $η$ values were studied. The $η$ values for the nuclei with odd mass number show an exponential decrease as a function of A or (N-Z). The $η$ values for the odd-odd type of nuclei appear to be constant, near one, up to the mass number 110 or (N-Z) of 13. Above these values, the $η$ values show exponential decrease. The $η$ values for even-even type nuclei decrease exponentially up to A equal to 142 or (N-Z) equal to 20. The values are lower than those for the nearby odd-odd type nuclei. The $η$ values increase for nuclei with A between 142 and 156 and (N-Z) between 20 and 28, and they finally reach the value of odd-odd type systematics.
Comments:
67+3 pages, 52+2 figures. Calculations with EMPIRE have been added to Section IV.3
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1708.04889 [pdf]
NPA(2018)·19 citations
03
[Submitted on 16 Aug 2017]
Theoretical estimates of the width of light-meson states in the SO(4) (2+1)-flavor limit
Tochtli Yépez-Martínez🇦🇷 · Osvaldo Civitarese🇦🇷 · Peter O. Hess🇲🇽
The low-energy sector of the mesonic spectrum exhibits some features which may be understood in terms of the SO(4) symmetry contained in the QCD-Hamiltonian written in the Coulomb Gauge. In our previous work we have shown that this is indeed the case when the Instantaneous Color-Charge Interaction (ICCI) is treated by means of non-perturbative many-body linearization techniques. Continuing along this line of description in this work we calculate the width of meson states belonging to the low portion of the spectrum (E <1 GeV ). In spite of the rather simple structure of the Hamiltonian used to calculate the spectra of pseudoscalar and vector mesons, the results for the width of these states follow the pattern of the data.
Comments:
8 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1708.04980 [pdf]
IJMPE(2018)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE

Charge symmetry breaking in light Λ hypernuclei

Mass number and excitation energy dependence of the Θeff​/Θrig​ parameter of the spin cut-off factor in the formation of an isomeric pair

Theoretical estimates of the width of light-meson states in the SO(4) (2+1)-flavor limit

Affiliations

Charge symmetry breaking in light $Λ$ hypernuclei

Mass number and excitation energy dependence of the $Θ_{e f f} / Θ_{r i g}$ parameter of the spin cut-off factor in the formation of an isomeric pair