Abstract
The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable B-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity √s=13 TeV pp collision sample corresponding to around 2.0 nb−1 collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation.
Highlights
Data recorded by tracking detectors are used to reconstruct the trajectories of charged particles and determine their momenta
A good description of the distribution of material in the inner detector is crucial for understanding the performance of track reconstruction within ATLAS
While the first two methods probe the barrel region of the inner detector, in particular the new detector components installed in Run 2, the track-extension efficiency method has sensitivity in the forward η region of 1.0 < |η| < 2.5, in which most of the refurbished pixel services reside
Summary
Data recorded by tracking detectors are used to reconstruct the trajectories of charged particles and determine their momenta. Photon conversion vertices is a traditional method to measure the material of tracking detectors [8], taking advantage of precise theoretical understanding of electromagnetic interaction processes. The description of hadronic interactions is complex and only phenomenologically modelled in the simulation Another complementary approach which is applicable to the all tracking acceptance is to measure the nuclear interaction rate of charged hadrons through hadronic interactions, referred to as the track-extension efficiency method. Using the hadronic interaction approach, ATLAS has performed measurements of the inner detector’s material in Run 1 of the LHC [9, 10]. This paper presents studies of the ATLAS Run 2 ID material using hadronic interactions, photon conversions and the track-extension efficiency measurement.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
