The ATLAS Inner Detector commissioning and calibration

TL;DR

This paper details the commissioning, calibration, and performance measurement of the ATLAS Inner Detector, including alignment, efficiency, and resolution metrics, based on cosmic-ray data collected during initial operation.

Contribution

It presents the first comprehensive in-situ calibration and performance assessment of the ATLAS Inner Detector using cosmic-ray events.

Findings

Hit efficiency and tracking trigger efficiencies near 100%

Transverse impact parameter resolution of 22.1 μm

Relative momentum resolution of (4.83±0.16)×10^{-4} pT

Abstract

The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data- taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and in-situ calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1+/-0.9 {\mu}m and a relative momentum resolution {\sigma}p/p = (4.83+/-0.16) \times 10-4 GeV-1 \times pT have been measured for high momentum tracks.