The CP-conserving contribution to the transverse muon polarization in K+→μ+νγ

Gudrun Hiller, Gino Isidori
1999 Physics Letters B  
We present a detailed estimate of the transverse muon polarization (P_T) due to electromagnetic final-state interactions in the decay K^+ →μ^+ νγ. 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 (10^-4), essentially due to the suppression factor α/4π^2. This enforces the sensitivity of P_T in probing extensions of the Standard
more » ... del 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.
doi:10.1016/s0370-2693(99)00653-x fatcat:ym74d5h3tngzljmmts3lcnk5ri