Author/Authors :
H. Outa، نويسنده , , S. Ajimura، نويسنده , , K. Aoki and M. Akahori، نويسنده , , A. Banu، نويسنده , , H.C Bhang، نويسنده , , T. Fukuda، نويسنده , , O. Hashimoto and H. Tamura، نويسنده , , J.I. Hwang، نويسنده , , S. Kameoka، نويسنده , , B.H. Kang، نويسنده , , E.H. Kim، نويسنده , , J.H. Kim، نويسنده , , M.J. Kim، نويسنده , , T. Maruta، نويسنده , , Y. Miura، نويسنده , , Y. Miyake، نويسنده , , T. Nagae ، نويسنده , , M. Nakamura، نويسنده , , S.N. Nakamura، نويسنده , , H. Noumi، نويسنده , , et al.، نويسنده ,
Abstract :
We performed a coincidence measurement of two nucleons emitted from the nonmesonic weak decay (NMWD) of 5ΛHe and 12ΛC 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 (5ΛHe) = 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→nn)/Γ(Λn→np). The Γn/Γp ratio was measured also for the NMWD of 12ΛC. It is also close to 0.5. Those ratios are consistent with recent theoretical calculations based on the heavy meson/direct quark exchange picture.
