Kang BH, Bhang H, Kim EH, Kim JH, Kim MJ, Yim HJ, Ajimura S, Miyake Y, Aoki K, Nagae T, Noumi H, Outa H, Saha PK, Sato Y, Sekimoto M, Toyoda A, Banu A, Fukuda T, Hashimoto O, Kameoka S, Miura Y, Nakamura SN, Okayasu Y, Takahashi T, Tamura H, Tsukada K, Watanabe T, Hwang JI, Maruta T, Nakamura M, Okada S, Park H, Tanida K. Exclusive measurement of the nonmesonic weak decay of the lambda(5)He hypernucleus.
PHYSICAL REVIEW LETTERS 2006;
96:062301. [PMID:
16605985 DOI:
10.1103/physrevlett.96.062301]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2005] [Indexed: 05/08/2023]
Abstract
We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay of lambda(5)He formed via the 6Li(pi+, 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 lambda p --> np and lambda n --> nn, respectively. The ratio of the nucleon pair numbers was N(nn)/N(np) = 0.45 +/- 0.11(stat) +/- 0.03(syst) in the kinematic region of cos theta(NN) < -0.8. Since each decay mode was exclusively detected, the measured ratio should be close to the ratio of gamma(lambda p --> np)/gamma(lambda n --> nn). The ratio is consistent with recent theoretical calculations based on the heavy meson and/or direct-quark exchange picture.
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