Measurement of the Transverse Polarization of Electrons Emitted in Free-Neutron Decay

Both components of the transverse polarization of electrons (σT1, σT2) emitted in the β-decay of polarized, free neutrons have been measured. The T-odd, P-odd correlation coefficient quantifying σT2, perpendicular to the neutron polarization and electron momentum, was found to be R=0.008±0.015±0.005. This value is consistent with time reversal invariance and significantly improves limits on the relative strength of imaginary scalar couplings in the weak interaction. The value obtained for the correlation coefficient associated with σT1, N=0.056±0.011±0.005, agrees with the Standard Model expectation, providing an important sensitivity test of the experimental setup.