Search for charginos nearly mass-degenerate with the lightest neutralino

A search for charginos with masses close to the mass of the lightest neutralino is reported, based on the data collected with the DELPHI detector at LEP from 1995 to 1997 at centre-of-mass energies between 130 and 183 GeV. The signature of a photon at high transverse momentum radiated from the initi...

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Bibliographic Details
Published in:The European physical journal. C, Particles and fields Particles and fields, 1999-11, Vol.11 (1), p.1-17
Main Author: Abreu et al, P.
Format: Article
Language:English
Subjects:
Apexes
Background radiation
Charged particles
Particle decay
Photons
Transverse momentum
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Summary:A search for charginos with masses close to the mass of the lightest neutralino is reported, based on the data collected with the DELPHI detector at LEP from 1995 to 1997 at centre-of-mass energies between 130 and 183 GeV. The signature of a photon at high transverse momentum radiated from the initial state reduces the two-photon background to acceptable rates, thus making the mass differences between a few hundred MeV/c\(^2\) and 3 GeV/c\(^2\) detectable. In very nearly degenerate scenarios, the lifetime of the chargino can be large enough to produce either visible secondary vertices or decays outside the detector; therefore, quasi-stable heavy charged particles and displaced decay vertices were also searched for. No excess of events with respect to the Standard Model expectations was observed, and limits in the plane of chargino-neutralino mass difference versus chargino mass are given.
ISSN:1434-6044
1434-6052
DOI:10.1007/s100529900156