The performance of the jet trigger for the ATLAS detector during 2011 data taking

TL;DR

This paper evaluates the performance of the ATLAS jet trigger system during 2011 data collection at the LHC, highlighting its efficiency, resolution, and operational thresholds for jet detection in high-energy collisions.

Contribution

It provides a detailed assessment of the jet trigger performance, including efficiency thresholds and energy resolution, during 2011 proton-proton and heavy ion collision data taking.

Findings

Trigger efficiency above 25 GeV for Level 1 seeded jets.

Full efficiency for offline jets above 60 GeV across trigger levels.

Jet energy resolution better than 4% centrally and 2.5% forward.

Abstract

The performance of the jet trigger for the ATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton-proton collisions with a centre-of-mass energy of 7 TeV and heavy ion collisions with a 2.76 TeV per nucleon-nucleon collision energy. The ATLAS trigger is a three level system designed to reduce the rate of events from the 40 MHz nominal maximum bunch crossing rate to the approximate 400 Hz which can be written to offline storage. The ATLAS jet trigger is the primary means for the online selection of events containing jets. Events are accepted by the trigger if they contain one or more jets above some transverse energy threshold. During 2011 data taking the jet trigger was fully efficient for jets with transverse energy above 25 GeV for triggers seeded randomly at Level 1. For triggers which require a jet to be identified at each of the three trigger levels, full efficiency is reached for offline jets with transverse energy above 60 GeV. Jets reconstructed in the Event Filter and corresponding to offline jets with transverse energy greater than 60 GeV, are reconstructed with a resolution in transverse energy of better than 4% in the central region and better than 2.5% in the forward direction.