Search for anomalous production of acoplanar di-lepton events in \({\rm e^+e^-}\) collisions at \(\sqrt{s} =\) 183 and 189 GeV

  • The OPAL Collaboration
  • G. Abbiendi et al.
Experimental physics


A selection of di-lepton events with significant missing transverse momentum has been performed using a total data sample of 237.4 pb\(^{-1}\) at \({\mathrm e}^+{\mathrm e}^-\) centre-of-mass energies of approximately 183 GeV and 189 GeV. The observed numbers of events – 78 at 183 GeV and 301 at 189 GeV – are consistent with the numbers expected from Standard Model processes, which arise predominantly from \(\mathrm{W}^+\mathrm{W}^-\) production with both W bosons decaying leptonically. This topology is also an experimental signature for the pair production of new particles that decay to a charged lepton accompanied by one or more invisible particles. Discrimination techniques are described that optimise the sensitivity to particular new physics channels. No evidence for new phenomena is apparent. Upper limits on the production cross-section times branching ratio squared for sleptons and for leptonically decaying charginos and charged Higgs are presented in a manner intended to minimise the number of model assumptions. Assuming a 100% branching ratio for the decay \(\tilde{\ell} ^\pm_R \rightarrow {\ell^\pm} \tilde{\chi}^0 _1\), where \(\tilde{\chi}^0 _1\) is the lightest neutralino, we exclude at 95% CL: right-handed smuons with masses below 82.3 GeV for \(m_{\tilde\mu^-} - m_{\tilde \chi^0_1} > 3\) GeV and right-handed staus with masses below 81.0 GeV for \(m_{\tilde\tau^-} - m_{\tilde{\chi}^0_1} > 8\) GeV. Right-handed selectrons are excluded at 95% CL for masses below 87.1 GeV for \(m_{\tilde{\mathrm e}^-} - m_{\tilde{\chi}^0_1} > 5\) GeV, within the framework of the Minimal Supersymmetric Standard Model assuming \(\mu < -100\) GeV and \(\tan{\beta} = 1.5\). Charged Higgs bosons, H\(^{\pm}\), are excluded at 95% CL for masses below 82.8 GeV, assuming a 100% branching ratio for the decay \(\mathrm{H}^{\pm} \rightarrow \tau^\pm \nu_\tau\).


Higgs Boson Transverse Momentum Pair Production Minimal Supersymmetric Standard Model Charged Lepton 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • The OPAL Collaboration
  • G. Abbiendi et al.
    • 1
  1. 1.Dipartimento di Fisica dell' Università di Bologna and INFN, 40126 Bologna, Italy IT

Personalised recommendations