Charged Current Universality and the MSSM

TL;DR

This paper investigates how supersymmetric radiative corrections within the MSSM could affect tests of charged current universality, potentially revealing details about superpartner spectra through precision measurements.

Contribution

It provides a detailed calculation of one-loop supersymmetric corrections to key weak decay processes and explores their implications for CKM unitarity and lepton flavor universality tests.

Findings

Corrections can be as large as 10^{-3} in relevant decay processes.

Comparison of CKM unitarity and pion decay ratios can probe superpartner spectra.

Supersymmetric effects could be detectable in precision weak decay measurements.

Abstract

We analyze the prospective impact of supersymmetric radiative corrections on tests of charged current universality involving light quarks and leptons. Working within the R-parity conserving Minimal Supersymmetric Standard Model, we compute the corresponding one-loop corrections that enter the extraction of the Cabibbo-Kobayashi-Maskawa matrix element $V_{ud}$ from a comparison of the muon-decay Fermi constant with the vector coupling constant determined from nuclear and neutron $\beta$-decay. We also revisit earlier studies of the corrections to the ratio $R_{e/\mu}$ of pion leptonic decay rates $\Gamma[\pi^+ \to e^+ \nu (\gamma)]$ and $\Gamma[\pi^+ \to \mu^+ \nu (\gamma)]$. In both cases, we observe that the magnitude of the corrections can be on the order of $10^{-3}$. We show that a comparison of the first row CKM unitarity tests with measurements of $R_{e/\mu}$ can provide unique probes of the spectrum of first generation squarks and first and second generation sleptons.