New bounds on trilinear R-parity violation from lepton flavor violating observables

TL;DR

This paper derives new, significantly improved bounds on trilinear R-parity violating couplings in the MSSM by analyzing lepton flavor violating processes, especially those involving the Z boson, and compares these with previous constraints.

Contribution

It provides the first comprehensive analysis of bounds on R-parity violating couplings from Z-mediated lepton flavor violation, including loop and tree-level processes, for heavy supersymmetric spectra.

Findings

Limits on R-parity violating couplings are improved by several orders of magnitude for heavy spectra.

Loop-induced Z-mediated processes dominate over photonic penguins in certain lepton flavor violations.

Constraints from Z decays and three-body decays are also established for benchmark scenarios.

Abstract

Many extensions of the leptonic sector of the Minimal Supersymmetric Standard Model (MSSM) are known, most of them leading to observable flavor violating effects. It has been recently shown that the 1-loop contributions to lepton flavor violating three-body decays $l_i \to 3 l_j$ involving the $Z^0$ boson may be dominant, that is, much more important than the usual photonic penguins. Other processes like $\mu$-$e$ conversion in nuclei and flavor violating $\tau$ decays into mesons are also enhanced by the same effect. This is for instance also the case in the MSSM with trilinear R-parity violation. The aim of this work is to derive new bounds on the relevant combinations of R-parity violating couplings and to compare them with previous results in the literature. For heavy supersymmetric spectra the limits are improved by several orders of magnitude. For completeness, also constraints coming from flavor violating $Z^0$-decays and tree-level decay channels $l \to l_i l_j l_k$ are presented for a set of benchmark points.