Charge symmetry breaking in the A=4 hypernuclei

Charge symmetry breaking (CSB) in the Lambda-nucleon strong interaction generates a charge dependence of Lambda separation energies in mirror hypernuclei, which in the case of the A = 4 mirror hypernuclei 0(+) ground states is sizable, Delta B-Lambda(J=0) equivalent to B-Lambda(J=0) (He-4(Lambda)) - B-Lambda(J=0) (H-4(Lambda)) = 230 +/- 90 keV, and of opposite sign to that induced by the Coulomb repulsion in light hypernuclei. Recent ab initio calculations of the (H-4(Lambda), He-4(Lambda)) mirror hypernuclei 0(g.s.)(+) and 1(exc)(+) levels have demonstrated that a Lambda - Sigma(0) mixing CSB model due to Dalitz and von Hippel (1964) is capable of reproducing this large value of Delta B-Lambda(J=0). These calculations are discussed here with emphasis placed on the leading-order chiral EFT hyperon-nucleon Bonn-Julich strong-interaction potential model used and the no-core shell-model calculational scheme applied. The role of one-pion exchange in producing sizable CSB level splittings in the A = 4 mirror hypernuclei is discussed. (C) 2016 Elsevier B.V. All rights reserved.