Constraints on R-parity violating couplings from lepton universality

TL;DR

This paper investigates how one-loop corrections in an R-parity violating MSSM affect lepton universality in W and Z decays, providing bounds on certain couplings and highlighting potential constraints from Upsilon decay measurements.

Contribution

It offers the first detailed analysis of R-parity violating couplings' effects on lepton universality in W and Z decays, updating bounds with current data.

Findings

Bounds on lambda' couplings are strengthened by Z decay data.

W decay bounds are less restrictive due to experimental limitations.

Upsilon invisible width could provide additional constraints.

Abstract

We analyze the one loop corrections to leptonic W and Z decays in an R-parity violating extension to the Minimal Supersymmetric Standard Model (MSSM). We find that lepton universality violation in the Z line-shape variables alone would strengthen the bounds on the magnitudes of the lambda' couplings, but a global fit on all data leaves the bounds virtually unchanged at |lambda'_{33k}| < 0.42 and |lambda'_{23k}| < 0.50 at the 2 sigma level. Bounds from W decays are less stringent: |lambda'_{33k}| < 2.4 at 2 sigma, as a consequence of the weaker Fermilab experimental bounds on lepton universality violation in W decays. We also point out the potential of constraining R-parity violating couplings from the measurement of the Upsilon invisible width.