Abstract
The reconstruction of particle trajectories in the tracking detectors of experiments at the Large Hadron Collider (LHC) is one of the most complex parts in analysing the data from beam-beam collisions. To maximise the integrated luminosity during Run-1 of the LHC data taking period, the number of simultaneous proton-proton interactions per beam crossing (pile- up) was steadily increased. The track reconstruction is the most time consuming reconstruction component and scales non-linearly in high luminosity environments. Flat budget projections (at best) for computing resources during the upcoming Run-2 of the LHC together with the demands of reconstructing higher pile-up collision data at rates more than double compared to Run-1 have put pressure on the track reconstruction software to meet the available computing resources. The ATLAS experiment has thus performed a two year long software campaign which led to a reduction of the reconstruction time for Run-2 conditions by a factor of four: a major part of the changes were improvements to the track reconstruction, which was reduced by more than a factor of five without any loss of output information for subsequent physics analysis. We present the methods used for analysing the software, the planning and deployment of updates and new methods implemented to optimise both algorithmic performance and event data.
Highlights
The Run-1 data taking of the Large Hadron Collider (LHC) from 2010 to 2012 marked a very successful period for high energy physics, concluding with the exciting discovery of the Higgs boson by both the ATLAS [1] and CMS [2] collaborations
The Inner Detector (ID) is designed to reconstruct trajectories from charged particles. It has a silicon pixel detector at the innermost radii, which is surrounded by a silicon strip detector and a drift straw tube detector (TRT) that identifies particle types using transition radiation
For Run-2, the seed purity was reinvestigated and an additional component has been introduced: since the ID was equipped with a new innermost pixel detector, the Insertable B-Layer [17], seeds formed from three space points are required to be confirmed by another space point in a different detector layer before the road search in the track finding module starts
Summary
This content has been downloaded from IOPscience. Please scroll down to see the full text. Ser. 664 072042 (http://iopscience.iop.org/1742-6596/664/7/072042) View the table of contents for this issue, or go to the journal homepage for more. Download details: IP Address: 188.184.3.56 This content was downloaded on 24/02/2016 at 09:43 Please note that terms and conditions apply. 21st International Conference on Computing in High Energy and Nuclear Physics (CHEP2015) IOP Publishing. Journal of Physics: Conference Series 664 (2015) 072042 doi:10.1088/1742-6596/664/7/072042
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