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Violation of CP and T in semileptonic decays due to scalar interactions

Observing charge-parity (CP) or time-reversal (T) violations in the leptonic sector will give useful information to elucidate the nature of neutrinos. CP-violating couplings in charged leptonic currents carry out the weak phases necessary to break these symmetries. Here we study the interference of $W^{\pm}$ and $H^{\pm}$ bosons mediated amplitudes as the origin of possible CP and T violation in semileptonic decays of $K^{\pm}$ mesons and $τ^{\pm}$ leptons. We use the experimental bound on the T-odd transverse polarization asymmetry in $K^+_{μ3}$ decays to predict an upper limit on the CP violating effects in $τ\to K πν$ decays. In the framework of this model with scalar-mediated interactions, we find that current limits on the former process indicate that the CP violating effects in the latter are much smaller than the limits reported so far.