Hypernuclear weak decay experiments at KEK: n-n and n-p coincidence measurement

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

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34 Citations (Scopus)


We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay (NMWD) of Λ5He and Λ12C formed via the (π+, K+) reaction. In both of n + p and n + n pair coincidence spectra, we observed a clean back-to-back correlation coming from the two-body decay of Λp → np and Λn → nn, respectively. We obtained the ratio of the nucleon pair numbers, Nnn/Nnp (Λ5He) = 0.45 ± 0.11 (stat) ± 0.03 (syst) in the kinematic region of cos θNN < -0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of Γ(Λp → nn)/Γ (Λp → np). The Γnp ratio was measured also for the NMWD of Λ12C. It is also close to 0.5. Those ratios are consistent with recent theoretical calculations based on the heavy meson/direct quark exchange picture.

Original languageEnglish
Pages (from-to)157-167
Number of pages11
JournalNuclear Physics A
Issue number1-4 SPEC. ISS.
Publication statusPublished - 2005 May 30

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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