First measurement of the T-violating muon polarization in the decay K+→μ+νγ

Abstract We present the result of the first measurement of the T-violating transverse muon polarization P T in the decay K + → μ + νγ . This polarization is sensitive to new sources of CP-violation in the Higgs sector. Using data accumulated in the period 1996–1998 we have obtained P T =(−0.64±1.85(stat)±0.10(syst))×10 −2 which is consistent with no T-violation in this decay.