In-medium Λ isospin impurity from charge symmetry breaking in the Λ4 H- Λ4 He mirror hypernuclei

The Λ separation energies in the mirror hypernuclei Λ4H-Λ4He exhibit large charge symmetry breaking (CSB). Analyzing this CSB within pionless effective field theory while using partially conserved baryon-baryon SU(3) flavor symmetry, we deduce a Λ-ς0 induced in-medium admixture amplitude AI=1≈1.5% in the dominantly isospin I=0Λ hyperon. Our results confirm the free-space value AI=1(0) inferred directly within the SU(3) baryon octet by Dalitz and von Hippel in 1964 and reaffirmed in a recent QCD+QED lattice calculation. Furthermore, exploring the consequences of SU(3) flavor symmetry on the Λ-nucleon interaction, we find that CSB is expected to impact the S=1 and S=0 spin channels in opposite directions, with the latter dominating by an order of magnitude. These observations explain a recent deduction of Λ-nucleon CSB strengths.