Search for the G-parity irregular term in weak nucleon currents extracted from mirror beta decays in the mass 8 system

[プレプリント]The alignment correlation terms in the beta-ray angular distributions from purely spin aligned Li-8 and B-8 have been measured to search for the G-parity violating induced tensor term g(II) in the weak nucleon currents. The g(II) was extracted from the present alignment correlation terms, combined with the known beta-alpha angular correlation terms and weak magnetism. This analysis permits an experimental determination of all the matrix elements necessary to extract g(II). As a result, the induced tensor terns was extracted as g(II)/g(A) = -0.28 +/- 0.28 (stat.) +/- 0.15 (syst.) at a 1 sigma (68%) level. The present data and the data in the mass A = 12 and 20 systems were analyzed under the KDR model in which medium effects including the off-shell effect and meson exchange current were taken into account. We determined the 1-body contribution to be zeta = -(0.13 +/- 0.13) x 10(-3) MeV-1 and the 2-body contribution to be lambda = +(0.27 +/- 0.97) x 10(-3) at a 1 sigma level. (c) 2008 Elsevier B.V. All rights reserved