The European Physical Journal C

ISSN: 1434-6044 (printed version)
ISSN: 1434-6052 (electronic version)

Table of Contents

Abstract Volume 1 Issue 1/2 (1998) pp 1-20

experimental physics:
Search for charginos, neutralinos and gravitinos at LEP

DELPHI Collaboration , P. Abreu et al. (21)

(21) LIP, IST, FCUL - Av. Elias Garcia, 14-1°, P-1000 Lisboa Codex, Portugal

Received: 8 August 1997

Abstract. An update of the searches for charginos and neutralinos in DELPHI is presented, based mainly on recent data collected at centre-of-mass energies of 161 GeV and 172 GeV. No signal is found. For a sneutrino with mass above 300 GeV/$c^2$ and a mass difference between the chargino and the lightest neutralino above 10 GeV/$c^2$, the lower limit at 95% confidence level on the chargino mass ranges from 84.3 GeV/$c^2$ to the kinematical limit (86.0 GeV/$c^2$), depending on the mixing parameters. The limit decreases for lower chargino-neutralino mass differences. The limit in the case of a light sneutrino is 67.6 GeV/$c^2$, provided that that there is no light sneutrino with a mass within 10 GeV$/c^2$ below the chargino mass. Upper limits on neutralino pair production cross-sections of about a picobarn are derived. The $(\mu,M_2)$ domain excluded in the MSSM-GUT scenario is determined by combining the neutralino and chargino searches. These results imply a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 24.9 GeV/$c^2$ for tan$\beta \ge 1$. The search has also been extended to the case where the lightest neutralino is unstable and decays into a photon and a gravitino.

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Online publication: December 11, 1997
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