A Simultaneous Measurement of the $b$-tagging Efficiency Scale Factor and the $t\bar{t}$ Production Cross Section at the Collider Detector at Fermilab

A Simultaneous Measurement of the $b$-tagging Efficiency Scale Factor and the $t\bar{t}$ Production Cross Section at the Collider Detector at Fermilab
Author:
Publisher:
Total Pages: 116
Release: 2011
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The ability to compare results between Monte Carlo and data is imperative in modern experimental high-energy physics analyses. The b-tagging efficiency Scale Factor (SF) allows for an accurate comparison of b quark identification in data samples and Monte Carlo. This thesis presents a simultaneous measurement of the SF for the SecVtx algorithm and the t{bar t} production cross section using 5.6 fb−1 of p{bar p} collision data at √s = 1.96 TeV collected by the Collider Detector at Fermilab (CDF) experiment. The t{bar t} cross section was measured to be 7.26 ± 0.47 pb, consistent with prior CDF analyses. The tight SF value was measured to be 0.925 ± 0.032 and the loose SF value was measured at 0.967 ± 0.033. These are the most precise SF SecVtx measurements to be performed at CDF to date.

A Simultaneous Measurement of the B-tagging Efficiency Scale Factor and the Tt Production Cross Section at the Collider Detector at Fermilab

A Simultaneous Measurement of the B-tagging Efficiency Scale Factor and the Tt Production Cross Section at the Collider Detector at Fermilab
Author: Nazim Hussain
Publisher:
Total Pages:
Release: 2011
Genre:
ISBN:

The ability to compare results between Monte Carlo and data is imperative in modern experimental high-energy physics analyses. The b-tagging efficiency Scale Factor (SF) allows for an accurate comparison of b quark identification in data samples and Monte Carlo. This thesis presents a simultaneous measurement of the SF for the SecVtx algorithm and the t t production cross section using 5.6 fb−1 of pp̄ collision data at √s = 1.96 TeV collected by the Collider Detector at Fermilab (CDF) experiment. The t t cross section was measured to be 7.26±0.47 pb, consistent with prior CDF analyses. The tight SF value was measured to be 0.925±0.032 and the loose SF value was measured at 0.967±0.033. These are the most precise SF SecVtx measurements to be performed at CDF to date.

Simultaneous Heavy Flavor Fractions and Top Cross Section Measurement at the Collider Detector at Fermilab

Simultaneous Heavy Flavor Fractions and Top Cross Section Measurement at the Collider Detector at Fermilab
Author:
Publisher:
Total Pages: 251
Release: 2010
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This dissertation describes the measurement of the top pair production cross section, using data from proton-antiproton collisions at a center-of-mass energy of 1.96 TeV, with 2.7 ± 0.2 fb−1 of data collected by the Collider Detector at Fermilab. Background contributions are measured concurrently with the top cross section in the b-tagged lepton-plus-jets sample using a kinematic fit, which simultaneously determines the cross sections and normalizations of t{bar t}, W + jets, QCD, and electroweak processes. This is the first application of a procedure of this kind. The top cross section is measured to be [sigma]{sub t{bar t}} = 7.64 ± 0.57(stat + syst) ± 0.45(lumi) pb and the Monte Carlo simulation scale factors K{sub Wb{bar b}} = 1.57 ± 0.25, K{sub Wc{bar c}} = 0.94 ± 0.79, K{sub Wc} = 1.9 ± 0.3, and K{sub Wq{bar q}} = 1.1 ± 0.3. These results are consistent with existing measurements using other procedures. More data will reduce the systematic uncertainties and will lead to the most precise of any single analysis to date.

Measurement of the $t\bar{t}$ Production Cross Section with an in Situ Calibration of $b$-jet Identification Efficiency

Measurement of the $t\bar{t}$ Production Cross Section with an in Situ Calibration of $b$-jet Identification Efficiency
Author:
Publisher:
Total Pages: 17
Release: 2010
Genre:
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A measurement of the top-quark pair-production cross section in p{bar p} collisions at √s = 1.96 TeV using data corresponding to an integrated luminosity of 1.12 fb−1 collected with the Collider Detector at Fermilab is presented. Decays of top-quark pairs into the final states e[nu] + jets and [mu][nu] + jets are selected, and the cross section and the b-jet identification efficiency are determined using a new measurement technique which requires that the measured cross sections with exactly one and multiple identified b-quarks from the top-quark decays agree. Assuming a top-quark mass of 175 GeV/c2, a cross section of 8.5 ± 0.6(stat.) ± 0.7(syst.) pb is measured.

Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S**ư

Measurement of the Ttbar Production Cross Section in Ppbar Collisions at S**ư
Author:
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Total Pages: 4
Release: 2005
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We present the measurement of the top quark pair production cross section in p{bar p} collisions at √s = 1.96 TeV using 318 pb−1 of data collected by the CDF detector at the Fermilab Tevatron. We measure the cross section in events with one high transverse momentum electron or muon, large missing transverse energy and three or more jets, where at least one bottom quarks from the top quark decay is identified via a secondary vertex tagging algorithm. The measured t{bar t} cross section is 8.7{sub -0.9}{sup +0.9}(stat){sub -0.9}{sup +1.2}(syst) pb, assuming a top quark mass of 178 GeV. The cross section measurement in the subsample in which both b-quark jets are identified gives 10.1{sub -1.4}{sup +1.6}(stat){sub -1.4}{sup +2.1}(syst) pb. We present one additional measurement of the t{bar t} cross section in the same dataset but without the b-tagging requirement. Top quark events are distinguished from the primary background of W boson production with associated jets using an artificial neural network method with a variety of kinematic quantities. This measurement uses a larger dataset albeit with a smaller t{bar t} fraction. The t{bar t} cross section without b-tagging is measured to be 6.0 ± 0.8(stat) ± 1.0(syst) pb.

Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**1/2

Measurement of the T Anti-t Production Cross Section in P Anti-p Collisions at S**1/2
Author:
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Total Pages: 7
Release: 2008
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We measure the t{bar t} production cross section in p{bar p} collisions at √s = 1.96 TeV in the lepton+jets channel. Two complementary methods discriminate between signal and background, b-tagging and a kinematic likelihood discriminant. Based on 0.9 fb−1 of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure [sigma]{sub t{bar t}} = 7.62 ± 0.85 pb, assuming the current world average m{sub t} = 172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top quark mass of 170 ± 7 GeV.

Measurement of the Top - Anti-top Production Cross Section at S**(/1/2)

Measurement of the Top - Anti-top Production Cross Section at S**(/1/2)
Author: DooKee Cho
Publisher:
Total Pages: 116
Release: 2005
Genre:
ISBN:

We discuss the measurement of the cross section for t{bar t} production in p{bar p} collisions at {radical}s = 1.96 TeV in e+jets final states observed at the D0 experiment at the Fermilab Tevatron. Our result is based on data collected from the June 2002 to September 2003 period of Run II of the p{bar p} Collider. In the Standard Model, the top quark is expected to decay mainly into a W boson and a b quark. The W boson can decay subsequently into a lepton and its neutrino or a q{bar q} quark-antiquark pair. In this thesis, we focus on the e{sup +} {nu}{sub e} or e{sup -} {bar {nu}}{sub e} decays of one of the W bosons and the q{bar q} decays of the other W boson in t{bar t} final states. The b, q and q' quarks appear as jets of particles in the detector, thereby defining the e+jets final state. We present two methods used for performing this measurement. The first method is based on a Random Grid Search (RGS) that minimizes the uncertainty on the extracted cross section. The variables used in the search take advantage of differences between expected background and signal processes to obtain the yield of t{bar t} events. The second method uses a Neural Network (NN) procedure that discriminates signal from background through the application of a NN trained on simulated t{bar t} signal and W+jets background events. The preliminary results presented in this thesis for inclusive t{bar t} production are {sigma}{sub p{bar p} {yields} t{bar t} + x} of 7.9{sub -2.4}{sup +2.6}(stat) {sub -2.3}{sup +2.2}(syst) {+-} 0.5 (L) pb for the NN analysis, where the uncertainties correspond to contributions from statistical and systematic sources and from the uncertainty on luminosity. Our measurements are consistent with each other, and are within error of the value of 6.77 {+-} 0.42 pb expected in the Standard Model.

The Large Hadron Collider

The Large Hadron Collider
Author: Thomas Schörner-Sadenius
Publisher: Springer
Total Pages: 554
Release: 2015-05-15
Genre: Science
ISBN: 3319150014

This comprehensive volume summarizes and structures the multitude of results obtained at the LHC in its first running period and draws the grand picture of today’s physics at a hadron collider. Topics covered are Standard Model measurements, Higgs and top-quark physics, flavour physics, heavy-ion physics, and searches for supersymmetry and other extensions of the Standard Model. Emphasis is placed on overview and presentation of the lessons learned. Chapters on detectors and the LHC machine and a thorough outlook into the future complement the book. The individual chapters are written by teams of expert authors working at the forefront of LHC research.