The supersymmetric prediction for the muon transverse polarization in the $K^{+}\leftarrow {\pi }^0{\mu }^{+}{\nu }_{\mu }$ decay

Abstract

The muon transverse polarization in the $K^{+}\leftarrow {\pi }^0{\mu }^{+}{\nu }_{\mu }$ decay will be measured at the $10^{-4}$ level in forthcoming experiments. We compare the phenomenological perspectives with the theoretical predictions in supersymmetric extensions of the standard model. In the minimal extension, CP-violating phases lead to a non-zero transverse polarization, that however is too small to account for a positive experimental signal. The problems that one encounters when departing from minimal assumptions are discussed. An observable effect is possible if the hypothesis of R-parity conservation is relaxed, but only at the price of assuming a very special pattern for the R-parity breaking couplings.

Comments: latex, 18 pages, 1 latex figure