Charge symmetry breaking in $\Lambda$ hypernuclei revisited

Abstract

The large charge symmetry breaking (CSB) implied by the $\Lambda$ binding energy difference $\Delta B_{\Lambda }^4(0_{g.s.}^{+})\equiv B_{\Lambda }{(}_{\Lambda }^4$He)$-$$B_{\Lambda }{(}_{\Lambda }^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 $\Lambda -{\Sigma }^0$ mixing. Using a schematic strong-interaction $\Lambda N\leftrightarrow \Sigma N$ coupling model developed by Akaishi and collaborators for $s$-shell $\Lambda$ hypernuclei, we revisit the evaluation of CSB in the $A=4$ $\Lambda$ hypernuclei and extend it to $p$-shell mirror $\Lambda$ hypernuclei. The model yields values of $\Delta B_{\Lambda }^4(0_{g.s.}^{+})\sim 0.25$ 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 ${}_{\Lambda }^{10}$B g.s. doublet splitting anticipated from the hyperon-nucleon strong-interaction spin dependence, thereby explaining the persistent experimental failure to observe the $2_{\mathrm{exc}}^{-}\to 1_{g.s.}^{-}$ $\gamma$-ray transition.

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

References in corpus (5)

• Charge Symmetry Breaking and QCD
• Observation of Lambda H-4 hyperhydrogen by decay-pion spectroscopy in electron scattering
• The hyperon-nucleon interaction: conventional versus effective field theory approach
• Structure of ${}_{\Lambda }^{10}$Be and ${}_{\Lambda }^{10}$B hypernuclei studied with the four-body cluster model
• Spectroscopy of Lambda-9Li by electroproduction

Cited by in corpus (8)

• Observation of Lambda H-4 hyperhydrogen by decay-pion spectroscopy in electron scattering
• Constraints on the $\Lambda$-neutron interaction from charge symmetry breaking in the ${}_{\mathbf{\Lambda }}^4\mathbf{He}$--${}_{\mathbf{\Lambda }}^4\mathbf{H}$ hypernuclei
• Nuclear physics uncertainties in light hypernuclei
• Measurement of ${}_{\mathrm{\Lambda }}^4\mathrm{H}$ and ${}_{\mathrm{\Lambda }}^4\mathrm{He}$ binding energy in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV
• Spectroscopy of $A=9$ hyperlithium by the $(e,e^{\prime }{K}^{+})$ reaction
• High Precision Momentum Calibration of the Magnetic Spectrometers at MAMI for Hypernuclear Binding Energy Determination
• Decay pion spectroscopy: a new approach
• Isospin breaking from diquark clustering