Time-reversal violation in beta decay in the standard model

We estimate the size of time-reversal violation in beta decay due to the Kobayashi-Maskawa phase delta, and the theta term L(t)heta. We find that the contribution of delta to the D and R correlations is not likely to be larger than of thp older of 10(-12)\a\(\s(2)s(3)s(delta)\/10(-3)) and 10(-14)\a\(\s(2)s(3)s(delta)\/10(-3)), respectively, where \a\ similar or equal to 1 fur neutron and Ne-19 decay. For the contribution of L theta to D and R we conclude that it is not likely to be larger than of the order of 10(-14)\a\(\theta\/3 x 10(-10))Q/(m(n) - m(p)) and 10(-12)\a\(\theta\/3 x 10(-10)), respectively (the present experimental limits on s(2)s(3)s(delta) and theta are \s(2)s(3)s(delta)\ less than or similar to 10(-3) and \theta\ less than or similar to 3 x 10(-10)), where Q is the energy release in the decay. For both delta and L-theta the D and R coefficients ate dominated by long-distance contributions. The small values of D and R in the standard model compared to the best experimental limit on T-odd correlations (10(-1) for D in Ne-19 decay) give potentially a wide window in which T-violating interactions beyond the standard model can be searched for. However, the range in this window that one will be able to exploit depends on the level at which the contributions of the final-state interactions can be kept under control.