Charge symmetry breaking in $\hat{I}›$ hypernuclei revisited

Abstract

The large charge symmetry breaking (CSB) implied by the $\hat{I}›$ binding energy difference $\hat{I}”B_{\hat{I}}^4›(0_{g.s.}^{+})\equiv B_{\hat{I}}›{(}_{\hat{I}}{›}^4$He)$-$$B_{\hat{I}}›{(}_{\hat{I}}{›}^4$H) = 0.35$\pm$0.06 MeV of the $A=4$ mirror hypernuclei ground states, determined from emulsion studies, has defied theoretical attempts to reproduce it in terms of CSB in hyperon masses and in hyperon-nucleon interactions, including one pion exchange arising from $\hat{I}›-\hat{I}{\pounds }^0$ mixing. Using a schematic strong-interaction $\hat{I}›N\leftrightarrow \hat{I}\pounds N$ coupling model developed by Akaishi and collaborators for $s$-shell $\hat{I}›$ hypernuclei, we revisit the evaluation of CSB in the $A=4$ $\hat{I}›$ hypernuclei and extend it to $p$-shell mirror $\hat{I}›$ hypernuclei. The model yields values of $\hat{I}”B_{\hat{I}}^4›(0_{g.s.}^{+})\sim 0.25$ MeV. Smaller size and mostly negative $p$-shell binding energy differences are calculated for the $A=7-10$ mirror hypernuclei, in rough agreement with the few available data. CSB is found to reduce by almost 30 keV the 110 keV ${}_{\hat{I}›}^{10}$B g.s. doublet splitting anticipated from the hyperon-nucleon strong-interaction spin dependence, thereby explaining the persistent experimental failure to observe the $2_{\mathrm{exc}}^{-}\to 1_{g.s.}^{-}$ ${\hat{I}}^3$-ray transition.

a few clarifying statements added to v2; matches published PLB version plus a note added after publication on p.13