Recent experimental results of weak decay of Λ hypernuclei and the long standing Γnp puzzle

H. Bhang, S. Ajimura, K. Aoki, T. Fukuda, T. Hasegawa, O. Hashimoto, H. Hotchi, S. Kameoka, B. Kang, J. Kim, M. Kim, Y. D. Kim, T. Kishimoto, K. Maeda, T. Maruta, S. Minami, T. Mori, T. Nagae, H. Noumi, Y. OhtaS. Okada, K. Omata, H. Outa, H. Park, H. Saito, A. Sakaguchi, R. Sawafuta, Y. Sato, M. Sekimoto, T. Shibata, Y. Shimizu, M. Sumihama, T. Takahashi, H. Tamura, L. I. Tang, K. Tanida, H. Yim, M. Youn

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1 Citation (Scopus)


In spite of notable progresses achieved at BNL and KEK during last decade, a consistent understanding of nonmesonic weak decay (NMWD) of Λ hypernuclei is yet to be achieved. Until recently, all the experimental data since the days of bubble chamber and emulsion showed the dominance of the neutron induced channel (Γn) over the proton induced one (Γp) in the NMWD of Λ hypernuclei, while the theoretical calculation predicted the predominance of the proton induced one. This inconsistency has been known as the famous 'Γnp puzzle' and the central focus in the study of the decay mechanism of the Λ hypernuclei and the baryonic weak interaction. However, important progresses have been made recently in both the experimental and theoretical sides. In this paper, the progresses in the experimental data on NMWD will be presented. The direct comparison of the recent proton and neutron spectra showed the Γnp ratio, 0.45 - 0.51 ± 0.15 (stat.) much less than unity. This ratio agrees well with the recent theoretical calculations. Though this outcome seems to indicate that the famous long standing puzzle has almost been resolved, the decay asymmetry still remains to be understood.

Original languageEnglish
Pages (from-to)943-957
Number of pages15
JournalActa Physica Polonica B
Issue number3
Publication statusPublished - 2004 Mar
EventXXVIII Mazurian Lakes Conference on Physics: Atomic Nucleus as a Laboratory for Fundamental Processes - Krzyze, Poland
Duration: 2003 Aug 312003 Sept 7


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