Search for Charginos with a Small Mass Difference with the Lightest Supersymmetric Particle at \sqrt{s} = 189 GeV

TL;DR

This paper reports a search for nearly mass-degenerate charginos at 189 GeV, using photon triggers to distinguish signals, setting new mass limits for charginos in scenarios with heavy scalar leptons.

Contribution

It introduces a novel search method for charginos with small mass differences, establishing the first mass limits in the heavy scalar lepton scenario.

Findings

No evidence for charginos was observed.

Upper limits on chargino production cross section were set.

Chargino mass limits were established for small mass differences.

Abstract

A search for charginos nearly mass-degenerate with the lightest supersymmetric particle is performed using the 176 pb^-1 of data collected at 189 GeV in 1998 with the L3 detector. Mass differences between the chargino and the lightest supersymmetric particle below 4 GeV are considered. The presence of a high transverse momentum photon is required to single out the signal from the photon-photon interaction background. No evidence for charginos is found and upper limits on the cross section for chargino pair production are set. For the first time, in the case of heavy scalar leptons, chargino mass limits are obtained for any \tilde{\chi}^{+-}_1 - \tilde{\chi}^0_1 mass difference.