We observed a distinct peak in the Λp invariant mass spectrum of 3He(K−, Λp)n, well below the mass threshold of mK + 2mp. By selecting a relatively large momentum-transfer region q = 350 ∼ 650 MeV/c, one can kinematically separate the peak from the quasi-free process, KN → KN followed by the non-resonant absorption by the two spectator-nucleons KNN → ΛN. We found that the simplest fit to the observed peak gives us a Breit-Wigner pole position at BKpp = 47 ± 3 (stat.) −+36 (sys.) MeV having a width ΓKpp = 115 ± 7 (stat.) −+1020 (sys.) MeV, and the S-wave Gaussian reaction form-factor parameter QKpp = 381 ± 14 (stat.) −+570 (sys.) MeV/c, as a new form of the nuclear bound system with strangeness - “K−pp”.
|Publication status||Published - 2018 May 30|
- Mesonic nuclear bound state
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