Commissioning of the ATLAS Level-1 Trigger with Cosmic Rays

TL;DR

This paper reports on the commissioning and testing of the ATLAS Level-1 trigger system using cosmic-ray muons, demonstrating its readiness for proton-proton collision data at CERN.

Contribution

It provides a detailed status update on the installation and in-situ commissioning of the ATLAS Level-1 trigger system with cosmic rays, a key step before collision data collection.

Findings

Successful commissioning of the Level-1 trigger components

Validation of trigger performance with cosmic-ray muons

Readiness for collision data processing

Abstract

The ATLAS detector at CERN's Large Hadron Collider will be exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system was designed to select potentially interesting events and reduce the incoming rate to 100-200 Hz. The first trigger level (LVL1) is implemented in custom-built electronics, the second and third trigger levels are realized in software. Based on calorimeter information and hits in dedicated muon-trigger detectors, the LVL1 decision is made by the central-trigger processor yielding an output rate of less than 100 kHz. The allowed latency for the trigger decision at this stage is less than 2.5 microseconds. Installation of the final LVL1 trigger system at the ATLAS site is in full swing, to be completed later this year. We present a status report of the main components of the first-level trigger and the in-situ commissioning of the full trigger chain with cosmic-ray muons.