ATLAS

Abstract:

The photoproduction of dijet events, where the two jets with the highest transverse energy are separated by a large gap in pseudorapidity, have been studied with the ZEUS detector using an integrated luminosity of 39 pb -1. Rapidity-gap events are defined in terms of the energy flow between the jets, such that the total summed transverse energy in this region is less than some value ETCUT. The data show a clear excess over the predictions of standard photoproduction models. This is interpreted as evidence for a strongly interacting exchange of a color-singlet object. Monte Carlo models which include such a color-singlet exchange are able to describe the data. © Springer-Verlag Berlin Heidelberg 2007.

Abstract:

We report a search for the anomalous production of events with multiple charged leptons in pp̄ collisions at s=1.96TeV using a data sample corresponding to an integrated luminosity of 346pb-1 collected by the CDFII detector at the Fermilab Tevatron. The search is divided into three-lepton and four-or-more-lepton data samples. We observe six events in the three-lepton sample and zero events in the 4-lepton sample. Both numbers of events are consistent with standard model background expectations. Within the framework of an R-parity-violating supergravity model, the results are interpreted as mass limits on the lightest neutralino (χ 10) and chargino (χ1±) particles. For one particular choice of model parameters, the limits are M(χ10)>110GeV/c2 and M(χ1±)>203GeV/c2 at 95% confidence level; the variation of these mass limits with model parameters is presented. © 2007 The American Physical Society.