Search for Chargino and Neutralino Production at sqrt{s} = 170 and 172 GeV at LEP

We search for inclusive high $E_T$ diphoton events with large missing transverse energy in $p\bar{p}$ collisions at $\sqrt{s}$=1.8 TeV. Such events are expected from pair production of charginos and neutralinos within the framework of the minimal supersymmetric standard model with a light gravitino. No excess of events is observed. In that model, and assuming gaugino mass unification at the GUT scale, we obtain a 95% CL exclusion region in the supersymmetry parameter space an...

Assuming that no supersymmetric signature will be found at the upgraded LEP collider we derive lower bounds on the masses of the four neutralinos $\tilde{\chi}_i^0$ in the Minimal Supersymmetric Standard Model (MSSM). We consider the recently published results from the search for the light chargino $\tilde{\chi}^\pm_1$ and the next-to-lightest neutralino $\tilde{\chi}^0_2$ at LEP1.5 and study the consequences of possible future lower $\tilde{\chi}^\pm_1$ and $\tilde{\chi}^0_2...

A search for chargino$-$neutralino pair production in three-lepton final states with missing transverse momentum is presented. The study is based on a dataset of $\sqrt{s} = 13$ TeV $pp$ collisions recorded with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 fb$^{-1}$. No significant excess relative to the Standard Model predictions is found in data. The results are interpreted in simplified models of supersymmetry, and statistically combined ...

The data collected by DELPHI in 1998 at the centre-of-mass energy of 189 GeV have been used to update the search for charginos nearly mass-degenerate with the lightest supersymmetric particle, which is assumed to be the lightest neutralino. Mass differences below \Delta M = 3 GeV/c^2 are considered. No excess of events with respect to the Standard Model expectation has been observed, and exclusions in the plane of \Delta M versus chargino mass are given. The new \Delta M inde...

A search for charginos nearly mass-degenerate with the lightest supersymmetric particle is performed using the 176 pb^-1 of data collected at 189 GeV in 1998 with the L3 detector. Mass differences between the chargino and the lightest supersymmetric particle below 4 GeV are considered. The presence of a high transverse momentum photon is required to single out the signal from the photon-photon interaction background. No evidence for charginos is found and upper limits on the ...

Searches for supersymmetric particles in channels with one or more photons and missing energy have been performed with data collected by the ALEPH detector at LEP. The data consist of 11.1 pb-1 at $\sqrt{s} = 161 GeV$, 1.1 pb-1 at 170 GeV and 9.5 pb-1 at 172 GeV. The e+e- -> nunu+photon cross section is measured. The data are in good agreement with predictions based on the Standard Model, and are used to set upper limits on the cross sections for anomalous photon production. ...

During the LEP2 operation, the 4 LEP experiments have collected data at centre-of-mass energies up to 209 GeV. Those data have been analysed in the search of charginos, neutralinos and sfermions in the framework of the Minimal Supersymmetric Standard Model (MSSM) with R-parity conservation and assuming the lightest neutralino to be the Lightest Supersymmetric Particle (SUGRA-model). No evidence for a signal was found in any of the channels. The results of each search were use...

If accessible at LEP II, chargino production is likely to be one of the few available supersymmetric signals for many years. We consider the prospects for the determination of fundamental supersymmetry parameters in such a scenario. The study is complicated by the dependence of observables on a large number of these parameters. We propose a straightforward procedure for disentangling these dependences and demonstrate its effectiveness by presenting a number of case studies at...

A search is described to detect charged Higgs bosons via the process e^+e^- -> H^+H^-, using data collected by the OPAL detector at center-of-mass energies of 130-172 GeV with a total integrated luminosity of 25 pb^-1. The decay channels are assumed to be H^+ -> qq'(bar) and H^+ -> \tau^+ \nu_{\tau}. No evidence for charged Higgs boson production is observed. The lower limit for its mass is determined to be 52 GeV at 95% confidence level, independent of the H^+ -> \tau^+ \nu_...

A search for associated production of charginos and neutralinos is performed using data recorded with the D0 detector at a ppbar center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. This analysis considers final states with missing transverse energy and three leptons, of which at least two are electrons or muons. No evidence for supersymmetry is found in a dataset corresponding to an integrated luminosity of 320 pb-1. Limits on the product of the production cr...