The alignment correlation terms in the -ray angular distributions from the purely spin aligned mirror pair 12 B( = 1 + 1 2 = 20.2 ms) and 12 N( = 1 + 1 2 = 11.0 ms) were precisely measured to place a new limit on the -parity conservation law. For the creation of the alignment, the spin manipulation technique was applied, which utilized the nuclear quadrupole interactions. Theparity violating induced tensor coefficient was determined to be 2 = 0 15 0 12 0 05 (theor.), which is consistent with the theoretical prediction based on QCD in which 2 is proportional to the mass difference between up and down quarks which constitute the nucleon. Also determined the axial charge to be = 4 90 0 10 (90% CL). From the result, we have found that the nucleon mass inside the nucleus is reduced (16 4)% relative to the free nucleon mass.
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