Leptonic Radiative Decay in Supersymmetry without R parity

TL;DR

This paper provides an exact numerical analysis of one-loop supersymmetric contributions to radiative lepton decays without R parity, deriving new bounds on parameters and highlighting potential observability in upcoming experiments.

Contribution

It introduces an exact, non-approximate calculation method for R-parity violating supersymmetric contributions to lepton radiative decays, updating previous constraints.

Findings

Major differences found in constraints on certain parameters compared to earlier analyses.

Constraints from neutrino masses were incorporated into the analysis.

Future experiments could observe decay rates predicted by the R-parity violating scenario.

Abstract

We present a detailed analysis together with exact numerical calculations on one-loop contributions to the branching ratio of the radiative decay of $\mu$ and $\tau$, namely $\mu \to e \gamma$, $\tau \to e \gamma$, and $\tau \to\mu \gamma$ from supersymmetry without R parity, focusing on contributions involving bilinear couplings. A numerical study is performed to obtain explicit bounds on the parameters under the present experimental limit. We present, and use in the calculation, formulas for exact mass eigenstate effective couplings. In this sense, we present an exact analysis free from approximation for the first time. After comparing our results against the closest early analysis, we discovered a major difference in resulted constraints on some ${\mu_i^*} {B_j}$ combinations. Constraints from neutrino masses on the parameters were considered. Our result indicates that the branching ratio measurement on $\mu \to e \gamma$ down to $10^{-13}-10^{-14}$ and beyond, as targeted by the MEG experiment, has a chance of observing decay from the R-parity violating scenario.