Measurements Of Top Quark Pair Production Cross Section In Proton Anti Proton Collisions At U221a S
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Measurements Of Top Quark Pair Production Cross Section In Proton Anti Proton Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2009
Measurements Of Top Quark Pair Production Cross Section In Proton Anti Proton Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
This dissertation presents a new measurement of p$ar{p}$ → t$ar{t}$X production at √s = 1.96 TeV using 974.2 pb-1of data collected with the D0 detector between 2002 and 2006. We focus on the final state where the W boson from one of the top quarks decays into a ? lepton and its associated neutrino, while the other W boson decays into a quark-antiquark pair. We aim to select those events in which the ? lepton subsequently decays hadronically, meaning to one or three charged hadrons, zero or more neutral hadrons and a tau neutrino (the charge conjugate processes are implied in all of the above). The observable signature thus consists of a narrow calorimeter shower with associated track(s) characteristic of a hadronic tau decay, four or more jets, of which two are initiated by b quarks accompanying the W's in the top quark decays, and a large net missing momentum in the transverse plane due to the energetic neutrino-antineutrino pair that leave no trace in the detector media. The preliminary result for the measured cross section is: ?(t$ar{t}$) = 6.9-1.2 +1.2(stat)-0.7+0.8(syst) ± 0.4 (lumi) pb. This indicates that our finding is consistent with the Standard Model prediction.
Measurements Of The Top Quark Pair Production Cross Section In Lepton Jets Final States Using A Topological Multivariate Technique As Well As Lifetime B Tagging In Proton Anti Proton Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2005
Measurements Of The Top Quark Pair Production Cross Section In Lepton Jets Final States Using A Topological Multivariate Technique As Well As Lifetime B Tagging In Proton Anti Proton Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Two alternative measurements of the t¯t production cross section at √s = 1.96 TeV in proton-antiproton collisions in the lepton+jets channel are presented. The t¯t production cross section is extracted by combining the kinematic event information in a multivariate discriminant. The measurement yields ?p¯p → t¯t + x = 5.13-1.57+1.76(stat)-1.10+0.96(syst) ± 0.33 (lumi) pb in the muon+jets channel, using 229.1 pb-1, and in the combination with the electron+jets channel (226.3 pb-1) ?p¯p → t¯t + x = 6.60-1.28+1.37(stat)-1.11+1.25(syst) ± 0.43 (lumi) pb. The second measurement presented reconstructs explicitly secondary vertices to d lifetime b-tagging. The measurement combines the muon+jets and the electron+jets channel, using 158.4 pb-1 and 168.8 pb-1, respectively: ?p¯p → t¯t + x = 8.24-1.25+1.34(stat)-1.63+1.89(syst) ± 0.54 (lumi) pb.
Measurements Of Top Quark Pair Production Cross Section In Proton Anti Proton Collisions At S 1 2
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Author :
language : en
Publisher:
Release Date : 2009
Measurements Of Top Quark Pair Production Cross Section In Proton Anti Proton Collisions At S 1 2 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
This dissertation presents a new measurement of p{bar p} → t{bar t}X production at √s = 1.96 TeV using 974.2 pb−1 of data collected with the D0 detector between 2002 and 2006. We focus on the final state where the W boson from one of the top quarks decays into a [tau] lepton and its associated neutrino, while the other W boson decays into a quark-antiquark pair. We aim to select those events in which the [tau] lepton subsequently decays hadronically, meaning to one or three charged hadrons, zero or more neutral hadrons and a tau neutrino (the charge conjugate processes are implied in all of the above). The observable signature thus consists of a narrow calorimeter shower with associated track(s) characteristic of a hadronic tau decay, four or more jets, of which two are initiated by b quarks accompanying the W's in the top quark decays, and a large net missing momentum in the transverse plane due to the energetic neutrino-antineutrino pair that leave no trace in the detector media. The preliminary result for the measured cross section is: [sigma](t{bar t}) = 6.9{sub -1.2}{sup +1.2}(stat){sub -0.7}{sup +0.8}(syst) ± 0.4 (lumi) pb. This indicates that our finding is consistent with the Standard Model prediction.
Measurement Of Top Quark Pair Production Cross Section In Proton Antiproton Collisions At Square Root S
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Author : Sohrab Hossain
language : en
Publisher:
Release Date : 2009
Measurement Of Top Quark Pair Production Cross Section In Proton Antiproton Collisions At Square Root S written by Sohrab Hossain and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with Collisions (Nuclear physics) categories.
Recueil Festival D Edimbourg 1947
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language : en
Publisher:
Release Date : 1949
Recueil Festival D Edimbourg 1947 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1949 with categories.
Measurement Of Top Anti Top Cross Section In Proton Anti Proton Collider At U221a S
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Author :
language : en
Publisher:
Release Date : 2005
Measurement Of Top Anti Top Cross Section In Proton Anti Proton Collider At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Discovery of the top quark in 1995 at the Fermilab Tevatron collider concluded a long search following the 1977 discovery of bottom (b) quark [1] and represents another triumph of the Standard Model (SM) of elementary particles. Top quark is one of the fundamental fermions in the Standard Model of electroweak interactions and is the weak-isospin partner of the bottom quark. A precise measurement of top pair production cross-section would be a test of Quantum Chromodynamics (QCD) prediction. Presently, Tevatron is the world's highest energy collider where protons (p) and anti-protons ($ar{p}$) collide at a centre of mass energy √s of 1.96 TeV. At Tevatron top (t) and anti-top ($ar{t}$) quarks are predominantly pair produced through strong interactions--quark annihilation (≅ 85%) and gluon fusion (≅ 15%). Due to the large mass of top quark, t or $ar{t}$ decays ( ̃10-25 sec) before hadronization and in SM framework, it decays to a W boson and a b quark with ̃100% branching ratio (BR). The subsequent decay of W boson determines the major signatures of t$ar{t}$ decay. If both W bosons (coming from t and $ar{t}$ decays) decay into leptons (viz., eve, ?v? or ?c?) the corresponding t$ar{t}$ decay is called dileptonic decay. Of all dileptonic decay modes of t$ar{t}$, the t$ar{t}$ → WWb$ar{b}$ → eve?v?b$ar{b}$ (e? channel) decay mode has the smallest background contamination from Z0 production or Drell-Yan process; simultaneously, it has the highest BR ( ̃3.16%) [2] amongst all dileptonic decay modes of t$ar{t}$. During Run I (1992-1996) of Tevatron, three e? candidate events were detected by D0 experiment, out of 80 candidate events (inclusive of all decay modes of t$ar{t}$). Due to the rarity of the t$ar{t}$ events, the measured cross-section has large uncertainty in its value (viz., 5.69 ± 1.21(stat) ± 1.04(sys) pb @ √s = 1.8 TeV measured by D0 [3]). This analysis presents a cross section measurement in e? channel utilizing ̃228 pb-1 of data collected by D0 experiment during Tevatron Run II (between June 2002 and April 2004).
Measurements Of The Top Quark Pair Production Cross Section In Lepton Jets Final States Using A Topological Multivariate Technique As Well As Lifetime B Tagging In Proton Anti Proton Collisions At S 1 2
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Author :
language : en
Publisher:
Release Date : 2006
Measurements Of The Top Quark Pair Production Cross Section In Lepton Jets Final States Using A Topological Multivariate Technique As Well As Lifetime B Tagging In Proton Anti Proton Collisions At S 1 2 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
Abstract Not Provided.
Measurements Of The Top Quark Pair Production Cross Section In Lepton Jets Final States Using A Topological Multivariate Technique As Well As Lifetime B Tagging Inproton Anti Proton Collisions At S 1 2
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Author : Tobias F. Golling
language : en
Publisher:
Release Date : 2005
Measurements Of The Top Quark Pair Production Cross Section In Lepton Jets Final States Using A Topological Multivariate Technique As Well As Lifetime B Tagging Inproton Anti Proton Collisions At S 1 2 written by Tobias F. Golling and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Two alternative measurements of the t{bar t} production cross section at {radical}s = 1.96 TeV in proton-antiproton collisions in the lepton+jets channel are presented. The t{bar t} production cross section is extracted by combining the kinematic event information in a multivariate discriminant. The measurement yields {sigma}{sub p{bar p} {yields} t{bar t} + x} = 5.13{sub -1.57}{sup +1.76}(stat){sub -1.10}{sup +0.96}(syst) {+-} 0.33 (lumi) pb in the muon+jets channel, using 229.1 pb{sup -1}, and in the combination with the electron+jets channel 226.3 pb{sup -1} {sigma}{sub p{bar p} {yields} t{bar t} + x} = 6.60{sub -1.28}{sup +1.37}(stat){sub -1.11}{sup +1.25}(syst) {+-} 0.43 (lumi) pb. The second measurement presented reconstructs explicitly secondary vertices to d lifetime b-tagging. The measurement combines the muon+jets and the electron+jets channel, using 158.4 pb{sup -1} and 168.8 pb{sup -1}, respectively: {sigma}{sub p{bar p} {yields} t{bar t} + x} = 8.24{sub -1.25}{sup +1.34}(stat){sub -1.63}{sup +1.89}(syst) {+-} 0.54 (lumi) pb.
Measurement Of The Top Quark Pair Production Cross Section In Dimuon Final States In Proton Antiproton Collisions At 1 96 Tev
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Author :
language : en
Publisher:
Release Date : 2008
Measurement Of The Top Quark Pair Production Cross Section In Dimuon Final States In Proton Antiproton Collisions At 1 96 Tev written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.
Particle physics deals with the fundamental building blocks of matter and their interactions. The vast number of subatomic particles can be reduced to twelve fundamental fermions, which interact by the exchange of spin-1 particles as described in the Standard Model (SM) of particle physics. The SM provides the best description of the subatomic world to date, despite the fact it does not include gravitation. Following the relation [lambda] = h/p, where h is Planck's constant, for the examination of physics at subatomic scales with size [lambda] probes with high momenta p are necessary. These high energies are accessible through particle colliders. Here, particles are accelerated and brought to collision at interaction points at which detectors are installed to record these particle collisions. Until the anticipated start-up of the Large Hadron Collider at CERN, the Tevatron collider at Fermilab near Chicago is the highest energy collider operating in the world, colliding protons and anti-protons at a center-of-mass energy of √s = 1.96 TeV. Its two interaction points are covered by the multi purpose particle detectors D0 and CDF. During the first data-taking period, known as Run I, the Tevatron operated at a center-of-mass energy of 1.8 TeV. This run period lasted from 1992 to 1996. During this period, the long-predicted top quark was discovered. From 1996 and 2001, the accelerator was upgraded to deliver higher instantaneous luminosities at its current center-of-mass energy. At the same time, the experiments were upgraded to take full advantage of the upgraded accelerator complex. The Tevatron is currently the only accelerator in the world with a sufficient energy to produce top quarks. Studying top quark production, decay and properties is an important part of the D0 and CDF physics programs. Because of its large mass, the top quark is a unique probe of the Standard Model, and an interesting environment to search for new physics. In this thesis, a measurement of the production cross-section of top quark pairs decaying to two muons is presented. In addition, a Monte Carlo study of the top quark spin correlation measurement was carried out. This thesis is laid out as follows: chapter two gives a short overview over the Standard Model of particle physics and the theoretical aspects of unpolarized and polarized top quark production and decay, chapter three describes the accelerator complex and the D0 experiment whose data is used in this analysis. The Reconstruction of events recorded with the D0 detector is explained in chapter four and the data and Monte Carlo samples used are presented in chapter five. Finally, the cross-section measurement is described in chapter six and the Monte Carlo study of top quark spin correlations in chapter seven.
Measurement Of The Top Quark Pair Production Cross Section In Dimuon Final States In Proton Antiproton Collisions At 1 96 Tev
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Author : Jens-Peter Konrath
language : en
Publisher:
Release Date : 2008
Measurement Of The Top Quark Pair Production Cross Section In Dimuon Final States In Proton Antiproton Collisions At 1 96 Tev written by Jens-Peter Konrath and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.