A new measurement of the beta emission asymmetry in the free decay of polarized neutrons

The beta asymmetry coefficient A0 was measured in the free decay of polarized neutrons by means of a time projection chamber in coincidence with plastic scintillators. A value of A0 = −0.1160(15) was measured and λ = gAgV = −1.266(4) deduced. Including recent results on the neutron lifetime the weak interaction coupling constants were determined as gV = 1.4172(34) × 10−62 J m3 and gA = −1.7944(20) × 10−62 J m3. The gV value is in excellent agreement with those from ft(0+ → 0+) and muon decay.