Evidence For Single Top Quark Production In The S Channel In Proton U2013 Proton Collisions At U221a S
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Evidence For Single Top Quark Production In The S Channel In Proton U2013 Proton Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2016
Evidence For Single Top Quark Production In The S Channel In Proton U2013 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 2016 with categories.
This Letter presents evidence for single top-quark production in the s-channel using proton–proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The analysis is performed on events containing one isolated electron or muon, large missing transverse momentum and exactly two b-tagged jets in the final state. The analysed data set corresponds to an integrated luminosity of 20.3 fb-1. The signal is extracted using a maximum-likelihood fit of a discriminant which is based on the matrix element method and optimized in order to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and W boson production in association with heavy-flavour jets. The measurement leads to an observed signal significance of 3.2 standard deviations and a measured cross-section of ?s = 4.8 ± 0.8(stat.)-1.3+1.6(syst.) pb, which is consistent with the Standard Model expectation. As a result, the expected significance for the analysis is 3.9 standard deviations.
Search For S Channel Single Top Quark Production In Proton U2013 Proton Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2014
Search For S Channel Single Top Quark Production In Proton U2013 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 2014 with categories.
This Letter presents a search at the LHC for s-channel single top-quark production in proton–proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb-1. Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of ?s=5.0 ± 4.3 pb, consistent with the Standard Model expectation.
Evidence For Electroweak Top Quark Production In Proton Antiproton Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2007
Evidence For Electroweak Top Quark Production In Proton Antiproton 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 2007 with categories.
We present the first evidence for electroweak single top quark production using nearly 1 fb-1 of Tevatron Run II data at √s = 1.96 TeV. We select single-top-like data events in the lepton+jets decay channel and separate them from backgrounds using the matrix element analysis method. This technique uses leading order matrix elements to compute an event probability for both signal and background hypotheses. Using the expected signal acceptance, background, and observed data we measure the single top quark cross section: ?(p$ar{p}$ → tb + tqb + X) = 4.6$+top{-1.5}$1.8 pb. The probability for the background to have fluctuated up to give at least the cross section measured in this analysis is 0.21%, which corresponds to a Gaussian equivalent significance of 2.9?.
Search For S Channel Single Top Quark Production In Proton Proton Collisions At Arrow
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Author :
language : en
Publisher:
Release Date : 2014
Search For S Channel Single Top Quark Production In Proton Proton Collisions At Arrow written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.
This Letter presents a search at the LHC for s-channel single top-quark production in proton-proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb-1. The selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of [sigma]s=5.0 " 4.3 pb, consistent with the Standard Model expectation.
Search For Anomalous Single Top Quark Production In Association With A Photon In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2016
Search For Anomalous Single Top Quark Production In Association With A Photon In Pp 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 2016 with categories.
We found the results of a search for flavor changing neutral currents (FCNC) through single top quark production in association with a photon is presented. The study is based on proton-proton collisions at a center-of-mass energy of 8 TeV using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 fb-1. The search for t? events where t → Wb andW → ?n is conducted in final states with a muon, a photon, at least one hadronic jet with at most one being consistent with originating from a bottom quark, and missing transverse momentum. Furthermore, there was no evidence of single top quark production in association with a photon through a FCNC is observed. Upper limits at the 95% confidence level are set on the tug and tcg anomalous couplings and translated into upper limits on the branching fraction of the FCNC top quark decays: B(t → u?) 1.3 x 10sup-4/sup and B(t →c?) 1.7 x 10
Search For S Channel Single Top Quark Production In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2016
Search For S Channel Single Top Quark Production In Pp Collisions At Sqrt 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 2016 with categories.
A search is presented for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quark containing a muon or an electron in the final state. The signal is extracted through a maximum-likelihood fit to the distribution of a multivariate discriminant defined using boosted decision trees to separate the expected signal contribution from background processes. Data collected at centre-of-mass energies of 7 and 8 TeV yield cross sections of 7.1 +/- 8.1 pb and 13.4 +/- 7.3 pb, respectively, and a best fit value of 2.0 +/- 0.9 for the combined ratio of the measured and expected values. The signal significance is 2.5 standard deviations, and the upper limit on the rate relative to the standard model expectation is 4.7 at 95% confidence level.
Evidence For S Channel Single Top Quark Production In P Bar P Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2013
Evidence For S Channel Single Top Quark Production In P Bar P Collisions At Sqrt 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 2013 with categories.
Search For Electroweak Single Top Quark Production In 1 96 Tev Proton Antiproton Collisions
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Author : Bernd Stelzer
language : en
Publisher:
Release Date : 2005
Search For Electroweak Single Top Quark Production In 1 96 Tev Proton Antiproton Collisions written by Bernd Stelzer 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.
This thesis describes the first search for electroweak single top quark production in proton-antiproton collisions at a center of mass energy of 1.96 TeV. The data sample used for this analysis corresponds to 162 pb{sup -1} recorded by the upgraded Collider Detector at Fermilab. The search is performed by doing a classic maximum likelihood fit to the H{sub T} distribution in data. The kinematic variable H{sub T} is the scalar sum of transverse energies of all final state particles in the event. This variable has the advantage that its distribution looks very similar for both contributing (s-channel and t-channel) single top processes, but is different for background processes. The combination of both channels to one signal improves the sensitivity of the search. No significant evidence for electroweak single top quark production is found and we set an upper limit at the 95% confidence level on the combined single top quark production cross section of 17.8 pb.
Search For Electroweak Single Top Quark Production In 1 96 Tev Proton Antiproton Collisions Microform
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Author : Stelzer, Bernd
language : en
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
Release Date : 2005
Search For Electroweak Single Top Quark Production In 1 96 Tev Proton Antiproton Collisions Microform written by Stelzer, Bernd and has been published by Library and Archives Canada = Bibliothèque et Archives Canada this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Physics Theses categories.
This thesis describes the first search for electroweak single top quark production in proton-antiproton collisions at a center of mass energy of 1.96 TeV. The data sample used for this analysis corresponds to 162 pb -1 recorded by the upgraded Collider Detector at Fermilab. The search is performed by doing a classic maximum likelihood fit to the H T distribution in data. The kinematic variable H T is the scalar sum of transverse energies of all final state particles in the event. This variable has the advantage that its distribution looks very similar for both contributing (s-channel and t-channel) single top processes, but is different for background processes. The combination of both channels to one signal improves the sensitivity of the search. No significant evidence for electroweak single top quark production is found and we set an upper limit at the 95% confidence level on the combined single top quark production cross section of 17.8 pb.
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.