München 2009 – scientific programme

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T: Fachverband Teilchenphysik

T 32: Elektroschwache Wechselwirkung 2

T 32.9: Talk

Tuesday, March 10, 2009, 18:45–19:00, A017

Study of Hadronic τ Decays in the ATLAS Detector with the W→τν Process — •Guilherme Nunes Hanninger, Jürgen Kroseberg, and Norbert Wermes — Physikalisches Institut, Bonn University

The ATLAS experiment at the LHC is expected to start taking data from proton-proton collisions with a center-of-mass energy of 10 TeV. The initial period of data acquisition with an instantaneous luminosity of 10³¹−10³² cm⁻²s⁻¹ might provide a unique possibility for the measurement of W→τν events and possibly the first observation of hadronically decaying τ leptons at LHC. However, as soon as the luminosity is increased to 10³³ cm⁻²s⁻¹, thresholds needed to limit trigger rates to the available bandwidth will be too high to efficiently collect signal events. The W→τν signal production cross section is σ×BR=1.7· 10⁴ pb at leading order and its signature consists of low transverse momentum W bosons, resulting in soft τ leptons and low missing transverse energy. The dominant background is the QCD multi-jet process with an expected cross section of approximately 10¹⁰ pb. The most critical part of this analysis is the trigger as it has to reduce the huge QCD jets background by several orders of magnitude and at the same time select a large fraction of signal events. The perspectives for the observation of the W→τν signal with an integrated luminosity of 100 pb⁻¹ will be discussed including different options of trigger requirements.