Search for SUSY with R-parity violating LL\bar{E} couplings at sqrt(s) = 189 GeV

TL;DR

This paper reports on a search for supersymmetric particles with R-parity violation at 189 GeV, setting new mass limits and constraints based on data from the DELPHI detector, with results consistent with the Standard Model.

Contribution

It provides the first constraints on SUSY particles with R-parity violating LLar{E} couplings at 189 GeV, updating previous limits and exploring both direct and indirect decay channels.

Findings

Mass limits: neutralino > 30 GeV/c^2, chargino > 94 GeV/c^2

Constraints on MSSM parameter space

Results consistent with Standard Model expectations

Abstract

Searches for pair production of supersymmetric particles under the assumption that R-parity is not conserved are presented, based on data recorded by the DELPHI detector in 1998 from e+e- collisions at a centre-of-mass energy of 189 GeV. Only one R-parity violating LL\bar{E} term (i.e. one lambda coupling), which couples scalar leptons to leptons, is considered to be dominant at a time. Moreover, it is assumed that the strength of the R-parity violating couplings is such that the lifetimes can be neglected. The search for pair production of neutralinos, charginos and sleptons has been performed for both direct R-parity violating decays and indirect cascade decays. The results are in agreement with Standard Model expectations, and are used to update the constraints on the MSSM parameter values and the mass limits previously derived at sqrt(s) = 183 GeV. The present 95% C.L. limits on supersymmetric particle masses are: m_{\tilde{\chi}^0} > 30 GeV/c^2 and m_{\tilde{\chi}^\pm} > 94 GeV/c^2; m_{\tilde{\nu}} > 76.5 GeV/c^2 (direct and indirect decays); m_{\tilde{\ell}_R} > 83 GeV/c^2 (indirect decay only).