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Title: Inclusive jet production studies at the Tevatron using the CDF detector

Abstract

Quantum Chromodynamics (QCD) is the gauge theory that governs the strong interactions between quarks and gluons inside hadrons like, for example, protons and neutrons. It shows two well established characteristics, related to the non-Abelian nature of the theory, that dominate its phenomenology: asymptotic freedom and color confinement. The dependence of the strong coupling, α s(Q 2), with the hard scale is such that it decreases with decreasing the distance between partons. This allows to perform precise theoretical calculations at large energy transfer (short distances) using perturbative QCD (pQCD). On the other hand, the strength of the interaction increases with the distance between partons and thus colored quarks and gluons are forced to be confined inside colorless hadrons.

Authors:
 [1]
  1. Autonomous Univ. of Barcelona, Bellaterra (Spain)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
915133
Report Number(s):
FERMILAB-THESIS-2007-08
TRN: US0804906
DOE Contract Number:
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COLOR; CONFINEMENT; ENERGY TRANSFER; FERMILAB COLLIDER DETECTOR; FERMILAB TEVATRON; GLUONS; HADRONS; NEUTRONS; PRODUCTION; PROTONS; QUANTUM CHROMODYNAMICS; QUARKS; STRONG INTERACTIONS; Experiment-HEP

Citation Formats

Francisco, Olga Norniella. Inclusive jet production studies at the Tevatron using the CDF detector. United States: N. p., 2007. Web. doi:10.2172/915133.
Francisco, Olga Norniella. Inclusive jet production studies at the Tevatron using the CDF detector. United States. doi:10.2172/915133.
Francisco, Olga Norniella. Thu . "Inclusive jet production studies at the Tevatron using the CDF detector". United States. doi:10.2172/915133. https://www.osti.gov/servlets/purl/915133.
@article{osti_915133,
title = {Inclusive jet production studies at the Tevatron using the CDF detector},
author = {Francisco, Olga Norniella},
abstractNote = {Quantum Chromodynamics (QCD) is the gauge theory that governs the strong interactions between quarks and gluons inside hadrons like, for example, protons and neutrons. It shows two well established characteristics, related to the non-Abelian nature of the theory, that dominate its phenomenology: asymptotic freedom and color confinement. The dependence of the strong coupling, αs(Q2), with the hard scale is such that it decreases with decreasing the distance between partons. This allows to perform precise theoretical calculations at large energy transfer (short distances) using perturbative QCD (pQCD). On the other hand, the strength of the interaction increases with the distance between partons and thus colored quarks and gluons are forced to be confined inside colorless hadrons.},
doi = {10.2172/915133},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}

Thesis/Dissertation:
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  • In this thesis we present the measurement of the inclusive isolated prompt photon cross section with a total integrated luminosity of 2.5 fb -1 of data collected with the CDF Run II detector at the Fermilab Tevatron Collider. The prompt photon cross section is a classic measurement to test perturbative QCD (pQCD) with potential to provide information on the parton distribution function (PDF), and sensitive to the presence of new physics at large photon transverse momentum. Prompt photons also constitute an irreducible background for important searches such as H → γγ, or SUSY and extra-dimensions with energetic photons in themore » final state. The Tevatron at Fermilab (Batavia, U.S.A.) is currently the hadron collider that operates at the highest energies in the world. It collides protons and antiprotons with a center-of-mass energy of 1.96 TeV. The CDF and the D0 experiments are located in two of its four interaction regions. In Run I at the Tevatron, the direct photon production cross section was measured by both CDF and DO, and first results in Run II have been presented by the DO Collaboration based on 380 pb -1. Both Run I and Run II results show agreement with the theoretical predictions except for the low p T γ region, where the observed and predicted shapes are different. Prompt photon production has been also extensively measured at fixed-target experiments in lower p T γ ranges, showing excess of data compared to the theory, particularly at high x T. From an experimental point of view, the study of the direct photon production has several advantages compared to QCD studies using jets. Electromagnetic calorimeters have better energy resolution than hadronic calorimeters, and the systematic uncertainty on the photon absolute energy scale is smaller. Furthermore, the determination of the photon kinematics does not require the use of jet algorithms. However, the measurements using photons require a good understanding of the background, mainly dominated by light mesons (π 0 and η) which decay into two very collinear photons. Since these photons are produced within a jet, they tend to be non-isolated in most of the cases, and can be suppressed by requiring the photon candidates to be isolated in the calorimeter. In the case the hard scattered parton hadronizes leaving most of its energy to the meson, the photon produced in the decay will not be surrounded by large energy depositions. To further reduce this remaining isolated background, we present a new technique based on the isolation distribution in the calorimeter. The measured cross section is compared to next-to-leading order (NLO) pQCD calculations, which have been corrected for non-perturbative contributions. This thesis is organized as follows: we start with a brief review of QCD theory and the formalism to calculate cross sections in Chapter 2, where we also introduce the physics of prompt photon production and summarize the current status of the prompt photon phenomenology. Chapter 3 contains a description of the Tevatron and the CDF detector. The experimental measurement is described in Chapter 4, where we provide details on the different datasets used in the measurement, the trigger, and the event selection requirements. Most of this Chapter is devoted to the explanation of the background subtraction method and the determination of the photon signal fraction. The systematic uncertainties on the measurement are evaluated in Chapter 5, while Chapter 6 discusses the final results and the comparison to the theoretical predictions. Finally, the conclusions are presented in Chapter 7.« less
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  • This dissertation describes a measurement of the rate of associated production of the W boson with the charm jet in the proton and anti-proton collisions at the center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. The measurement has direct sensitivity to the strange quark content inside the proton. A direct measurement of the momentum distribution of the strange quark inside the proton is essential for a reliable calculation of new physics signal as well as the background processes at the collider experiments. The identification of events containing a W boson and a charm jet is based on themore » leptonic decays of the W boson together with a tagging technique for the charm jet identification based on the semileptonic decay of the charm quark into the muon. The charm jet recoiling against the W boson must have a minimum transverse momentum of 20 GeV and an absolute value of pseudorapidity less than 2.5. This measurement utilizes the data collected by the D0 detector at the Fermilab Collider. The measured rate of the charm jet production in association with the W boson in the inclusive jet production with the W boson is 0.074 ± 0.023, which is in agreement with the theoretical predictions at the leading order in Quantum Chromodynamics.« less