The CP-conserving contribution to the transverse muon polarization in K~+ -> #mu#~+ #nu##gamma#

摘要

We present an estimate of the transverse muon polarization (P_T) due to electromagnetic final-state interactions in the decay K~+ -> #mu#~+ #nu##gamma#. This CP-conserving effect represents the dominant contribution to P_T within the Standard Model. As a result of an explicit calculation, we find that the CP-conserving contribution to P_T is quite small, typically of O(10~(-4)), essentially due to the suppression factor #alpha#/4#pi#~2. This enforces the sensitivity of P_T in probing extensions of the Standard Model with new sources of time-reversal violations. A brief discussion about possible CP-violating contributions to P_T in the framework of supersymmetric models with unbroken R-parity is also presented.