"K−pp", a [formula omitted]-meson nuclear bound state, observed in 3He(K−,Λp)n reactions.

Abstract We observed a distinct peak in the Λ p invariant mass spectrum of He 3 (K − , Λ p) n , well below m K + 2 m p , i.e. , the mass threshold of the K − to be bound to two protons. By selecting a relatively large momentum-transfer region q = 350 ∼ 650 MeV/ c , one can kinematically separate the peak from the quasi-free process, K ‾ N → K ‾ N followed by the non-resonant absorption by the two spectator-nucleons K ‾ N N → Λ N. We found that the simplest fit to the observed peak gives us a Breit–Wigner pole position at B Kpp = 47 ± 3 (s t a t.) − 6 + 3 (s y s.) MeV having a width Γ Kpp = 115 ± 7 (s t a t.) − 20 + 10 (s y s.) MeV, and the S -wave Gaussian reaction form-factor parameter Q Kpp = 381 ± 14 (s t a t.) − 0 + 57 (s y s.) MeV/ c , as a new form of the nuclear bound system with strangeness – " K − p p ". [ABSTRACT FROM AUTHOR]