Jet physics at ATLAS

Clements, Daniel Robert (2008) Jet physics at ATLAS. PhD thesis, University of Glasgow.

Abstract

The use and optimisation of integration grid techniques to generate next-to-leading order predictions of jet cross-sections, independent of parton distribution functions, was investigated. Such methods were found to provide an accurate approximation to a standard Monte-Carlo simulation (within 1%) and enable collider data to be readily included in global PDF fitting procedures. However, the benefit of including inclusive-jet cross-section data from ATLAS in global fits is only significant if the jet energy scale (JES) can be constrained to ~1% at high pT.

Uncertainties in the theoretical prediction of the inclusive-jet cross-section such as PDFs and fixed-order (scale) uncertainties were studied and compared with experimental errors arising from jet energy resolution and absolute scale. These uncertainties were then considered in the context of a quark compositeness search where a sensitivity to a compositeness scale of Lambda<10TeV can be achieved with 10 inverse femtobarns of data, if the jet energy scale can be constrained to ~1%. An analysis using dijet angular distributions found a similar sensitivity without the dependence on the jet energy scale.

A potential method of evaluating the stability of the jet energy scale out to high pT by `bootstrapping' the calibration at low pT by the use of multi-jet events was also investigated. This suggests that a calorimeter non-linearity can be detected for jets with pT>500GeV at ~1.5%/500GeV (i.e. a 1.5% change in JES over 500GeV in pT).

An investigation of inner-detector commissioning issues associated with the ATLAS Semiconductor Tracker (SCT), including a review of `noisy' modules on the SCT Barrel (from May 2007) was carried out. In addition a tool for DCS monitoring within the online monitoring framework was developed and tested during the M5 and M6 commissioning weeks. Finally, a method of assessing the track reconstruction efficiency by track-insertion was considered for the particular case of minimum bias events.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: ATLAS, Inclusive Jets, PDF Errors, Jet Energy Scale, Integration grids, SCT, track insertion, PDF fits.
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Supervisor's Name: Buttar, Dr. Craig
• Date of Award: 2008
• Depositing User: Mr Daniel Clements
• Unique ID: glathesis:2008-365
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 07 Nov 2008
• Last Modified: 10 Dec 2012 13:18
• URI: https://theses.gla.ac.uk/id/eprint/365