DOI 10.1007/s100529901059
Search for chargino and neutralino production at
-184 GeV at LEP
The OPAL Collaboration
G.Abbiendi 2 - et al.
2Dipartimento di Fisica dell' Università di Bologna and INFN, I-40126 Bologna, Italy
Received: 19 August 1998 / Published online: 11 March 1999
Abstract
A search for charginos and neutralinos,
predicted by supersymmetric theories, has been
performed using a data sample of 57 pb-1
at centre-of-mass energies of 181-184 GeV taken
with the OPAL detector at LEP.
No evidence for chargino or neutralino production has been found.
Upper limits on chargino and neutralino pair production
(,
) cross-sections are obtained
as a function of the chargino mass (
),
the lightest neutralino mass (
)and the second lightest neutralino mass (
).
For large chargino masses the limits have been improved
with respect to the previous analyses at lower centre-of-mass energies.
Exclusion regions at 95% confidence level (C.L.) of parameters of the
Constrained Minimal Supersymmetric Standard Model are determined
for the case of a large universal scalar mass, m0,
implying heavy scalar fermions,
and for the case of a small m0 resulting in light
scalar fermions and giving the worst-case limits.
Within this framework and for
GeV
the 95% C.L. lower limits on
for m0=500 GeV
are 90.0 and 90.2 GeV for
and 35 respectively.
These limits for all m0 (the worst-case) are 69.1 and 65.2 GeV
for
and 35 respectively.
Exclusion regions are also presented for neutralino masses, including
an absolute lower limit at 95% C.L. for the mass of the lightest neutralino
of 30.1 GeV for m0 = 500 GeV
(24.2 GeV for all m0),
with implications for experimental searches for the lightest neutralino as
a dark matter candidate.
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