Search for stop production in R-parity-violating supersymmetry at HERA

TL;DR

This paper reports a search for stop quark production via R-parity-violating interactions at HERA, setting limits on model parameters due to the absence of observed signals.

Contribution

First search for stop production in R-parity-violating supersymmetry at HERA, providing new constraints on model parameters.

Findings

No evidence for stop production was observed.

Limits were set on the R-parity-violating coupling $ ext{λ'}_{131}$.

Constraints were derived within the MSSM and minimal Supergravity models.

Abstract

A search for stop production in R-parity-violating supersymmetry has been performed in $e^{+}p$ interactions with the ZEUS detector at HERA, using an integrated luminosity of 65 pb$^{-1}$. At HERA, the R-parity-violating coupling $\lambda'$ allows resonant squark production, $e^+d\to\tilde{q}$. Since the lowest-mass squark state in most supersymmetry models is the light stop, $\tilde{t}$, this search concentrated on production of $\tilde{t}$, followed either by a direct R-parity-violating decay, or by the gauge decay to $b\tilde{\chi}^+_{1}$. No evidence for stop production was found and limits were set on $\lambda'_{131}$ as a function of the stop mass in the framework of the Minimal Supersymmetric Standard Model. The results have also been interpreted in terms of constraints on the parameters of the minimal Supergravity model.