ALEPH Four-Jet Excess, $R_b$ and $R-$Parity Violation

Abstract

We review briefly the indications for some relatively light superpartners based on the ~$R_b$ ~anomaly and discuss the dependence of the potential increase in $R_b$ on the assumption about ~$R-$parity (non)conservation. We point out that the exotic 4-jet events reported by ALEPH may constitute a signal for supersymmetry with such a light spectrum and with explicitly broken $R-$parity. A parton level simulation shows that production of a pair of light charginos with their subsequent baryon-number violating decays (either through a stop or through a neutralino) could possibly give rise to this excess. The decay $\chi^- \ra \tilde{t}_R^\ast b \ra d s b$ with $m_{\chi^-_1} \sim 60 \gev$ and $m_{\tilde t} \sim 52 \gev$ leads to signatures very close to the experimental observations.