Exclusive measurement of the nonmesonic weak decay of the heΛ5 hypernucleus

B. H. Kang, H. Bhang, E. H. Kim, J. H. Kim, M. J. Kim, H. J. Yim, S. Ajimura, Y. Miyake, K. Aoki, T. Nagae, H. Noumi, H. Outa, P. K. Saha, Y. Sato, M. Sekimoto, A. Toyoda, A. Banu, T. Fukuda, O. Hashimoto, S. KameokaY. Miura, S. N. Nakamura, Y. Okayasu, T. Takahashi, H. Tamura, K. Tsukada, T. Watanabe, J. I. Hwang, T. Maruta, M. Nakamura, S. Okada, H. Park, K. Tanida

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58 Citations (Scopus)


We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay of HeΛ5 formed via the Li6(π+,K+) reaction. The energies of the two nucleons and the pair number distributions in the opening angle between them were measured. In both np and nn pairs, we observed a clean back-to-back correlation coming from the two-body weak reactions of Λp→np and Λn→nn, respectively. The ratio of the nucleon pair numbers was Nnn/Nnp=0.45±0.11(stat)±0.03(syst) in the kinematic region of cosθNN<-0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of Γ(Λp→np)/Γ(Λn→nn). The ratio is consistent with recent theoretical calculations based on the heavy meson and/or direct-quark exchange picture.

Original languageEnglish
Article number062301
JournalPhysical Review Letters
Issue number6
Publication statusPublished - 2006


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