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Title: Diffractive processes in antiproton-proton collision at √s = 1.96 TeV in the D0 experiment

Abstract

A first study of single diffractive central high-p T dijet events in p$$\bar{p}$$ collisions at center-of-mass energy √s = 1.96 TeV is presented, using data recorded by the D0 detector at the Tevatron during RunIIa in 2002-2004. The total integrated luminosity corresponding to the data sample is 398 pb -1. A diffractive sample is selected using a rapidity gap approach. A precise definition of the rapidity gap constitutes the first part of the thesis. The rapidity gap is defined by means of two parts of the D0 detector--luminosity detectors and calorimeter. Luminosity detectors serve as a basic indicators of diffractive candidates and the calorimeter is used to confirm the low energy activity in the forward region (a rapidity gap). Presented studies of energy deposited in forward part of calorimeter by various types of events yield two rapidity gap definitions. Both of them use a fixed rapidity interval in calorimeter |η| ϵ [2.6,5.2] and introduce an upper limit on the energy deposited in this region. First definition, which corresponds to the lowest systematical errors, uses a limit of 10 GeV, an energy limit in the second definition is set to 3 GeV. This alternative definition corresponds to the lowest contamination of diffractive sample by non-diffractive events, on the other hand it is accompanied with rejection of high percentage of diffractive candidates. Using the gap definition dijet diffractive data are then selected and compared to inclusive dijet events in various distributions. The main focus is to measure the difference in azimuthal angles between two leading jets in events with at least two high p t central jets. This variable is sensitive to the dynamics of the process. Indeed, the results show the different behavior of ΔΦ distributions between the inclusive and diffractive samples. It is also shown that this difference is bigger for lower p T jets. Other distributions presented in the thesis show that most of the properties are the same for inclusive and diffractive events. The only observed difference is in the transversal properties of the jets, which could be explained as that diffractive jets are narrower than inclusive ones. Results are compared to Monte Carlo Pomwig (for diffractive sample) and Herwig (for inclusive sample); both show a good agreement with the data.

Authors:
 [1]
  1. Czech Technical Univ., Prague (Czech Republic)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
936340
Report Number(s):
FERMILAB-THESIS-2006-65
TRN: US0805587
DOE Contract Number:
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CALORIMETERS; CONTAMINATION; FERMILAB TEVATRON; LUMINOSITY; PARTICLE RAPIDITY; Experiment-HEP

Citation Formats

Otec, Roman. Diffractive processes in antiproton-proton collision at √s = 1.96 TeV in the D0 experiment. United States: N. p., 2006. Web. doi:10.2172/936340.
Otec, Roman. Diffractive processes in antiproton-proton collision at √s = 1.96 TeV in the D0 experiment. United States. doi:10.2172/936340.
Otec, Roman. Sun . "Diffractive processes in antiproton-proton collision at √s = 1.96 TeV in the D0 experiment". United States. doi:10.2172/936340. https://www.osti.gov/servlets/purl/936340.
@article{osti_936340,
title = {Diffractive processes in antiproton-proton collision at √s = 1.96 TeV in the D0 experiment},
author = {Otec, Roman},
abstractNote = {A first study of single diffractive central high-pT dijet events in p$\bar{p}$ collisions at center-of-mass energy √s = 1.96 TeV is presented, using data recorded by the D0 detector at the Tevatron during RunIIa in 2002-2004. The total integrated luminosity corresponding to the data sample is 398 pb-1. A diffractive sample is selected using a rapidity gap approach. A precise definition of the rapidity gap constitutes the first part of the thesis. The rapidity gap is defined by means of two parts of the D0 detector--luminosity detectors and calorimeter. Luminosity detectors serve as a basic indicators of diffractive candidates and the calorimeter is used to confirm the low energy activity in the forward region (a rapidity gap). Presented studies of energy deposited in forward part of calorimeter by various types of events yield two rapidity gap definitions. Both of them use a fixed rapidity interval in calorimeter |η| ϵ [2.6,5.2] and introduce an upper limit on the energy deposited in this region. First definition, which corresponds to the lowest systematical errors, uses a limit of 10 GeV, an energy limit in the second definition is set to 3 GeV. This alternative definition corresponds to the lowest contamination of diffractive sample by non-diffractive events, on the other hand it is accompanied with rejection of high percentage of diffractive candidates. Using the gap definition dijet diffractive data are then selected and compared to inclusive dijet events in various distributions. The main focus is to measure the difference in azimuthal angles between two leading jets in events with at least two high pt central jets. This variable is sensitive to the dynamics of the process. Indeed, the results show the different behavior of ΔΦ distributions between the inclusive and diffractive samples. It is also shown that this difference is bigger for lower pT jets. Other distributions presented in the thesis show that most of the properties are the same for inclusive and diffractive events. The only observed difference is in the transversal properties of the jets, which could be explained as that diffractive jets are narrower than inclusive ones. Results are compared to Monte Carlo Pomwig (for diffractive sample) and Herwig (for inclusive sample); both show a good agreement with the data.},
doi = {10.2172/936340},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Thesis/Dissertation:
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  • Measurements of the inclusive diffractive Z → μ +μ - cross section with gap requirement for M μμ > 40 GeV at √s = 1.96 TeV and fraction of Z bosons produced diffractively with gap requirement from Z inclusive production are presented. The measurements are performed using a data sample corresponding to an integrated luminosity of 820 pb -1, collected with the D0 detector at the Tevatron, between 2002 to 2005. A total of 39945 di-muons events are selected and final results of: σmore » $$gap\atop{Diff}$$ x Br(Z/γ* → μ +μ -) = 4.09 ± 0.64(stat.) ± 0.88(syst.) ± 0.27(lumi.) pb and, R$$gap\atop{Diff}$$ = 1.92 ± 0.30(stat.) ± 0.41(syst.) ± 0.12(lumi) % are obtained. In addition, dσ/dζ and dσ/dy distributions are presented and they are compared with diffractive montecarlo (POMWIG). A reasonable agreement is obtained in this comparation. Finally, comparison of fraction of Z bosons produced diffractively with gap requirement (gap fraction) as measured with D0 during Run I of the Tevatron is compared. A good agreement is found for gap fraction results.« less
  • The analysis described in this dissertation uses the Forward Proton Detectors(FPD) installed at the DØ detector in Tevatron collider at Fermilab to measure the single diffractive differential cross section dσ/d|t| at √s = 1.96 TeV center of mass energy. The single diffractive events were selected using the DØ central detector and the Forward proton detectors and |t| of the forward protons are measured using the FPD system. The analysis presents the measurement of the differential cross section of the single di ractive events as a function of |t| in the range 0.2 < |t|< 1.3 GeV 2. The differential crossmore » section measurement is within the theoretical and experimental expectations. The total single diffractive cross section( σ sd) in the region 0.0 < |t|< 1.3 GeV 2 is found to be 9.682 0.048 (stat.) 1.219 (syst.) mb.« less
  • A measurement of the top pair production cross section in the dimuon final state for proton-antiproton collisions at √s = 1.96 TeV is presented. Approximately 420 pb -1 of data collected with the Run II D0 detector are used for this measurement. Two data events are observed with a total expected signal plus background yield of 3.6 events. Assuming a top mass of 175 GeV, the measured cross section is: σ tmore » $$\bar{t}$$= 3.13$$+4.17\atop{-2.60}$$(stat)$$+0.92\atop{-0.86}$$(sys)±0.19(lumi)pb, which is consistent with a NNLO prediction of 6.77 ± 0.42 pb.« less
  • A search for Supersymmetry is performed via the associated production of charginos and neutralinos in fi states consisting of three charged leptons and missing transverse energy using data collected with the DØ detector at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron Collider. The data sample corresponds to an integrated luminosity of ~ 2.3 fb -1. This fi state is considered one of the most promising channels in the search for supersymmetric particles because of its low Standard Model background. A dedicated event selection is developed and events with two muons plus an additional isolated track or eventsmore » with two electrons plus an additional isolated track are analyzed. The requirement of an isolated track replaces the third charged lepton in the event. After all selection cuts are applied, in total 7 events are selected in the data with an expected number of background events of 5.24±0.40 (stat)±0.30 (syst). Due to the good agreement of events observed in data with the expectation of the Standard Model backgrounds, no evidence for Supersymmetry is found. The present analyses are considered in combination with three other decay channels and limits on the production cross section times leptonic branching fraction are set. The results are interpreted in a constrained scenario and exclusion regions are derived as a function of m 0 and m 1/2.« less
  • The Forward Proton Detector (FPD) is a new sub-system of the D0 detector, a 5000 ton particle physics detector located at the Fermilab Tevatron proton-antiproton collider. The FPD was implemented for the Tevatron Run II and gives access to a wide range of diffractive scattering processes, where one or both of the beam particles remain intact. The analysis described in this thesis makes use of the dipole spectrometer of the FPD to tag outgoing antiprotons in events that have a dijet signature in the central D0 calorimeter. Properties of jets with a diffractive tag signature are compared to jets withoutmore » such a signature yielding the first observation of tagged diffractive dijets at a 1.96 TeV center-of-mass energy.« less