Production of Heavy Helium 5Hе in the Absorption of Stopped Pions by 10,11B Nuclei

Abstract

Helium ⁵Hе states are sought in missing-mass (MM) spectra from reactions of the absorption of stopped pions: ¹⁰В(π⁻, dt)Х and ¹¹В(π⁻, tt)Х. The experiment is conducted using the LANL accelerator equipped with a two-arm semiconductor charged-particle spectrometer. The parameters of the ground state agree with the literature data. The best fit for the first excited level is obtained at E_r = 1.8(5) MeV and Γ = 4.7(7) MeV. Neither of the two reactions produce statistically significant evidence for the presence of highly excited (E_x ≥ 20 MeV) states of ⁵Hе.