"\mathbf\textit K^-\textit p\textit p", a K-Meson Nuclear Bound State, Observed in ³\rm He(K^-, Λ p)n Reactions

2018/05/31 by PARC E15 Collaboration, Ajimura, S., Asano, H. +67
#FOS: Physical sciences #Nuclear Experiment (nucl-ex)

paper · doi:10.48550/arxiv.1805.12275

Abstract

We observed a distinct peak in the Λp invariant mass spectrum of ³\rm He(K^-, Λp)n, well below the mass threshold of m_K + 2 m_p. By selecting a relatively large momentum-transfer region q = 350 ∼ 650 MeV/c, one can clearly 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 B_\rm \it Kpp = 47 ± 3 (stat.) ⁺³_-6 (sys.) MeV having a width Γ_\rm \it Kpp = 115 ± 7 (stat.) ⁺¹⁰_-9 (sys.) MeV, and the S-wave Gaussian reaction form-factor parameter Q_\rm \it Kpp = 381 ± 14 (stat.) ⁺⁵⁷_-0 (sys.) MeV/c, as a new form of the nuclear bound system with strangeness -- "K^-pp".

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