Density Dependence in Σ-Atoms and Implications for Σ Hypernuclei

The measured strong-interaction energy shifts, widths and yields of Σ − atomic levels over the periodic table are fitted by using a density dependent Σ nucleus optical potential V opt Σ . The best fit solutions for V opt Σ depart considerably from a standard t eff ρ ( r ) form in that the real part tends to flip sign, e. g. from attraction for Re V opt Σ outside the nucleus to repulsion inside. However, the quality of the atomic data is too poor to determine unambiguously V opt Σ inside the nucleus. For such density dependent potentials, single-particle hypernuclear states are likely to be unbound.