Results are presented of inclusive measurements of π± momentum spectra from K- absorption at rest in liquid helium. We found a peak in the π- spectrum at ΔM≡M ( Σ 4 He)-M(4He)=267.7±0.3 (statistical) -0.1 +1.1 (systematic) MeV (B Σ +=3.2 MeV). The width of the peak was deduced to be 4.6±0.5 (statistical) -1.3 +1.6 (systematic) MeV. The (K-, π+) spectrum does not exhibit a clear peak in the Σ- bound region. Comparison of these two spectra suggests that the peak in the π- spectrum is due to the formation of the S=0, I=1/2 ground state of Σ 4 He.
- 13.75.Ev - Hyperon-nucleon interactions (energy ≤ 10 GeV)
- 21.80 - Hypernuclei
- 25.80.Nv - Kaon-induced reactions and scattering