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T: Teilchenphysik

T 104: Neue Ph
änomene I

T 104.4: Talk

Monday, March 10, 2003, 17:10–17:25, SFO3

Search for events with isolated tau leptons and large missing transverse momentum in ep collisions at HERA — •Damir Lelas¹, Tancredi Carli², Dominik Dannheim¹, and Chi-Nhan Nguyen¹ — ¹DESY, Notkestrasse 85, 22607 Hamburg — ²CERN, European Organisation for Nuclear Research, CH-1211 Geneva 23, Switzerland

Motivated by the search for Standard Model or exotic W production events containing isolated tau leptons and large missing transverse momentum were selected from a data sample of the ZEUS experiment, which corresponds to 130 pb⁻¹ of integrated luminosity. The analysis strategy followed that employed in the search for isolated electrons and muons. Isolated tracks coming from putative hadronic tau decays were selected. Observables based on the internal jet structure were exploited to discriminate between tau decays and quark- and gluon-induced jets. Three tau candidates were found, while 0.23 ± 0.06 were expected from Standard Model processes, mainly from charged current deep inelastic scattering and W^±-boson production. A more restrictive selection was applied in order to isolate events from single top-quark production ep → etX → eWbX, where the W boson decays to W → τ ν, followed by a hadronic tau decay. Two candidate events were found, while 0.12 ± 0.02 events were expected from Standard Model background.