Alignment of the Atlas Inner Detector

TL;DR

This paper discusses the alignment procedures and performance of the ATLAS Inner Detector, crucial for precise particle tracking, based on data collected from cosmic rays and early proton-proton collisions at the LHC.

Contribution

It provides an overview of the alignment strategy and evaluates the alignment performance using 7 TeV collision data.

Findings

Alignment corrections achieved from cosmic-ray and 0.9 TeV data

Performance validated with 7 TeV collision data

Precise detector alignment essential for accurate physics measurements

Abstract

ATLAS is one of the two general purpose detectors at the world's largest particle accelerator, the Large Hadron Collider (LHC). The LHC will be colliding proton beams at a center of mass energy {\surd}s= 14 TeV and is currently operating at {\surd}s = 7 TeV. During the commissioning phase since September 2008, the ATLAS recorded cosmic-rays data and proton-proton collisions at {\surd}s = 0.9 TeV. This data has extensively been used for the alignment and calibration of various sub-detectors. The ATLAS detector has a precision tracking system installed around the beam pipe for the measurements of the position and momentum of charged particles emerging from the collisions. The precise knowledge of misalignments of the tracking devices is crucial for the important physics measurements. At the time of writing the alignment corrections were obtained from the cosmic-rays and 0.9 TeV proton-proton collisions data, while the large statistics of proton-proton collisions at 7 TeV was used to check the performance of the alignment. This article gives an overview of the alignment strategy and the alignment performance using the data collected from proton-proton collisions at 7 TeV.