Effect of nucleon structure variation in super-allowed Fermi beta-decay

Abstract

There is a well known anomaly between the value of the Fermi decay constant extracted from super-allowed Fermi beta-decay of nuclear isotriplets and that required by unitarity of the Cabibbo-Kobayashi-Maskawa matrix. This discrepancy remains at the level of a few tenths of a percent after the most rigorous investigation of conventional nuclear and radiative corrections. Within the framework of the quark-meson coupling model of nuclear matter, which has been previously applied successfully to phenomena such as nuclear saturation and nuclear charge symmetry violation, we show that it is possible to understand a significant fraction of the observed anomaly.

Nucleon and hadron structure changes in the nuclear medium and the impact on observables

“…To get an idea of the mass number dependence for the strange hypernuclei calculated, we show the absolute values of the scalar and vector potentials for the hyperons in 17 Y O, 41 Y Ca and 209 Y Pb (Y = Λ, Σ 0 , Ξ 0 ) in Figs. 21 and 22.…”

“…It may be possible to extend the QMC model to study such CSB in nuclei [18,39]. The change of the form factors due to the substructure effect of the nucleon may also give a previously unknown correction to the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element, V ud , from super-allowed Fermi β-decay [40,41]. To draw more definite conclusions, there is, however, a need for further investigation.…”

Compact stars within a soft symmetry energy quark-meson-coupling model

“…In the QMC model, the nucleon in nuclear medium is assumed to be a static spherical MIT bag in which quarks interact with the scalar (σ ) and vector (ω, ρ) fields, and those are treated as classical fields in the mean-field approximation (MFA) [8,9]. The quark field, ψ q i , inside the bag then satisfies the equation of motion:…”

“…The quark-meson-coupling (QMC) model [8][9][10] is an effective nuclear model that takes into account the internal structure of the nucleon explicitly. Within the QMC model, matter at low densities and temperatures is a system of nucleons interacting through meson fields, with quarks and gluons confined within MIT bags [11].…”

Deconfinement in the quark meson coupling model

“…The QMC model thus incorporates explicitly the quark degrees of freedom. This simple model was later refined by including the nucleonic fermi motion and the center-of-mass correction [8] to the bag energy and applied to a variety of problems [9,10].…”