The ATLAS b-Jet Trigger

TL;DR

The paper discusses the implementation and performance of the b-jet trigger system in the ATLAS experiment, which enhances event selection efficiency for physics analyses involving b-jets during 2011 data collection.

Contribution

It presents the design, optimization, and performance results of the dedicated b-jet trigger system used in ATLAS for 2011 data taking.

Findings

Increased b-jet acceptance and background reduction.

Effective use of lower energy thresholds and b-tagging techniques.

Improved rejection factors for multi-b-jet topologies.

Abstract

The online event selection is crucial to reject most of the events containing uninteresting background collisions while preserving as much as possible the interesting physical signals. The b-jet selection is part of the trigger strategy of the ATLAS experiment and a set of dedicated triggers was contributing to the event selection for the 2011 running. The b-jets acceptance is increased and the background reduced by lowering jet transverse energy thresholds at the first trigger level and applying b-tagging techniques at the subsequent levels. Different physics channels, especially topologies containing more than one b-jet where higher rejection factors are achieved, benefit from using the b-jet trigger. An overview of the b-jet trigger menu and performance on data is presented.