Speaker
Mr
Oleg Brandt
(University of Oxford)
Description
The Large Hadron Collider (LHC) at CERN is the world largest particle
accelerator. It will collide two proton beams at an unprecedented center of
mass energy of 14 TeV. ATLAS is equipped with a charge particle tracking
system built on two technologies: silicon and drift tube based detectors,
composing the ATLAS Inner Detector (ID). The alignment of the tracking
system poses a challenge as one should solve a linear equation with almost
36000 degrees of freedom. The required precision for the alignment of the
most sensitive coordinates of the silicon sensors is just a few microns. This
limit comes from the requirement that the misalignment should not worsen the
resolution of the track parameter measurements by more than 20%. So far the
proposed alignment algorithms are exercised on several applications. We will
present the outline of the alignment approach and results using real data from
cosmic rays and large scale computing simulation of physics samples mimicking the
ATLAS operation during real data taking. The full alignment chain is tested
using that stream and alignment constants are produced and validated within
24 hours. Cosmic ray data serves to produce an early alignment of the real
ATLAS Inner Detector even before the LHC start up. The impact of the
alignment on physics measurements will be discussed.
