Search for charginos in e+e- interactions at sqrt(s) = 189 GeV

TL;DR

This study updates the search for charginos and gravitinos at 189 GeV using DELPHI data, setting new mass limits and excluding certain MSSM parameter domains, but finds no evidence of these particles.

Contribution

It provides the first search results at 189 GeV with improved mass limits and constrains MSSM parameters by combining chargino and neutralino searches.

Findings

No evidence for charginos or gravitinos was observed.

Mass limits for charginos are 4-5 GeV/c^2 higher than previous at 183 GeV.

Lightest neutralino mass is constrained to be above 31.0 GeV/c^2 for tan(beta) ≥ 1.

Abstract

An update of the searches for charginos and gravitinos is presented, based on a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by combining the chargino searches with neutralino searches at the Z resonance implies a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.