The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Measurement of the Inclusive Jet Cross Section in pp̅ Collisions at √s̅ = 1.96 TeV
Mikko Voutilainen
Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Information and Natural Sciences for public examination and debate in Auditorium K216 at Helsinki University of Technology (Espoo, Finland) on the 1st of July, 2008, at 12 noon.
Dissertation in PDF format (ISBN 978-952-10-3723-8) [4412 KB]
Dissertation is also available in print (ISBN 978-952-10-3722-1)
Abstract
This thesis studies the high-energy collisions of protons and antiprotons. The data used in the measurement were collected during 2004–2005 with the DØ detector at the Tevatron Collider of the Fermi National Accelerator Laboratory and correspond to 0.7 fb−1 of integrated luminosity. High energy hadron collisions usually produce collimated sprays of particles called jets. The energy of the jets is measured using a liquid Argon-Uranium calorimeter and the production angle is determined with the help of silicon microstrip and scintillating fiber trackers. The inclusive jet cross section in proton-antiproton collisions is measured as a function of jet transverse momentum pT in six bins of jet rapidity at the center-of-mass energy √s̅ = 1.96 TeV. The measurement covers jet transerve momenta from 50 GeV up to 600 GeV and jet rapidities up to |y| = 2.4.
The data are collected using a set of seven single jet triggers. Event and jet cuts are applied to remove non-physical backgrounds and cosmic-ray interactions. The data are corrected for jet energy calibration, cut and trigger efficiencies and finite jet pT resolution. The corrections are determined from data and the methods are tested with Monte Carlo simulation. The main experimental challenges in the measurement are the calibration of jet energies and the determination of the jet pT resolution. New methods are developed for the jet energy calibration that take into account physical differences between the γ+jet and dijet calibration samples arising from quark and gluon jet differences. The uncertainty correlations are studied and provided as a set of uncertainty sources.
The production of particle jets in hadron collisions is described by the theory of quantum chromodynamics (QCD). When the transverse jet momentum is large, the contributions from long-distance physics processes are small and the production rates of jets can be predicted by perturbative QCD. The inclusive jet cross section in pp̅ collisions at large pT is directly sensitive to the strong coupling constant (αs) and the parton distribution functions (PDFs) of the proton. This measurement can be used to constrain the PDFs, in particular the gluon PDF at high proton momentum fraction x, and to look for quark substructure at the TeV scale. The data are compared to the theory predictions with perturbative QCD in the next-to-leading order precision and a good agreement between data and theory is observed.
Keywords: inclusive jet cross section, QCD, PDF, gluon, jet energy scale
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© 2008 Helsinki University of Technology
Last update 2011-05-26