2018 Impact factor 4.843
Particles and Fields
Eur. Phys. J. C 14, 187-198
DOI 10.1007/s100520000346

Search for chargino and neutralino production
at $\sqrt{s} = 189$ GeV at LEP

The OPAL Collaboration

G.Abbiendi$^{\rm 2}$ - et al.

2 Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy

Received: 14 October 1999 / Published online: 6 March 2000 - © Springer-Verlag 2000

Abstract
A search for charginos and neutralinos, predicted by supersymmetric theories, is performed using a data sample of 182.1 pb-1taken at a centre-of-mass energy of 189 GeV with the OPAL detector at LEP. No evidence for chargino or neutralino production is found. Upper limits on chargino and neutralino pair production ( $\tilde{\chi}^+_1 \tilde{\chi}^-_1$, $\tilde{\chi}^0 _1 \tilde{\chi}^0 _2$) cross-sections are obtained as a function of the chargino mass ( $m_{\tilde{\chi}^\pm_1}$), the lightest neutralino mass ( $m_{\tilde{\chi}^0 _1}$) and the second lightest neutralino mass ( $m_{\tilde{\chi}^0 _2}$). Within the Constrained Minimal Supersymmetric Standard Model framework, and for $m_{\tilde{\chi}^\pm_1} - m_{\tilde{\chi}^0 _1} \geq 5$ GeV, the 95% confidence level lower limits on $m_{\tilde{\chi}^\pm_1}$are 93.6 GeV for $\tan \beta = 1.5$ and 94.1 GeV for $\tan \beta = 35$. These limits are obtained assuming a universal scalar mass $m_0 \geq$ 500 GeV. The corresponding limits for all m0 are 78.0 and 71.7 GeV. The 95% confidence level lower limits on the lightest neutralino mass, valid for any value of $\tan \beta$are 32.8 GeV for $m_0 \geq 500$ GeV and 31.6 GeV for all m0.


Copyright Società Italiana di Fisica, Springer-Verlag 2000