Observation Of Top Quark Pairs Produced In Association With A Vector Boson In Pp Collisions At U221a S
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Observation Of Top Quark Pairs Produced In Association With A Vector Boson In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2016
Observation Of Top Quark Pairs Produced In Association With A Vector Boson 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.
Measurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of 19.5 fb-1, collected by the CMS experiment at the LHC. We found that final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from tt-W or tt-Z decays. The tt-W cross section is measured to be 382+117 -102 fb with a significance of 4.8 standard deviations from the background-only hypothesis. The tt-Z cross section is measured to be 242+65 -55 fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the tt-W and tt-Z cross sections.
Observation Of Top Quark Pairs Produced In Association With A W Or Z Boson In Pp Collisions At The Lhc
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Author : Andrew Brinkerhoff
language : en
Publisher:
Release Date : 2015
Observation Of Top Quark Pairs Produced In Association With A W Or Z Boson In Pp Collisions At The Lhc written by Andrew Brinkerhoff and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Observation Of Top Quark Pair Production In Association With A Photon And Measurement Of The Tt U00af Production Cross Section In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2015
Observation Of Top Quark Pair Production In Association With A Photon And Measurement Of The Tt U00af Production Cross Section 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 2015 with categories.
A search is performed for top-quark pairs (tt¯) produced together with a photon (?) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 tt¯? candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 ± 26 and 120 ± 39 non-tt¯? background events, respectively. The production of tt¯? events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯? production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is ?fidtt¯? × BR = 63 ± 8(stat)+17–13(syst) ± 1(lumi) fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48 ± 10 fb.
Measurement Of Top Quark Antiquark Pair Production In Association With A W Or Z Boson In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2014
Measurement Of Top Quark Antiquark Pair Production In Association With A W Or Z Boson 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 2014 with categories.
A measurement of the cross section for the production of top quark-antiquark pairs (${\mathrm {t}}\overline{{\mathrm {t}}}$) in association with a vector boson V (W or Z) in proton-proton collisions at $\sqrt{s} = 8$ $\, \text {TeV}$ is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb$^{-1}$ recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and $\mu$) channels: a same-sign dilepton analysis targeting ${\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W} $ events, and trilepton and four-lepton analyses designed for ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}} $ events. In the same-sign dilepton channel, the ${\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W} $ cross section is measured as $\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} \mathrm {W}} = 170 ^{+90-80}\, \text {(stat)} \pm 70\, \text {(syst)} \, \text {fb} $, corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}} $ cross section, $\sigma _{{\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {Z}}} = 200 ^{+80-70}\, \text {(stat)} ^{+40-30}\, \text {(syst)} \mathrm{fb}^{-1} $, is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive ${\mathrm {t}}\overline{{\mathrm {t}}} {\mathrm {V}} $ process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.
Observation Of The Associated Production Of A Single Top Quark And A W Boson In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2014
Observation Of The Associated Production Of A Single Top Quark And A W Boson 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 2014 with categories.
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 New Phenomena With Top Quark Pairs In Final States With One Lepton Jets And Missing Transverse Momentum In Pp Collisions At Square Root S
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Author : ATLAS Collaboration CERN
language : en
Publisher:
Release Date : 2021
Search For New Phenomena With Top Quark Pairs In Final States With One Lepton Jets And Missing Transverse Momentum In Pp Collisions At Square Root S written by ATLAS Collaboration CERN and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Abstract: A search for new phenomena with top quark pairs in final states with one isolated electron or muon, multiple jets, and large missing transverse momentum is performed. Signal regions are designed to search for two-, three-, and four-body decays of the directly pair-produced supersymmetric partner of the top quark (stop). Additional signal regions are designed specifically to search for spin-0 mediators that are produced in association with a pair of top quarks and decay into a pair of dark-matter particles. The search is performed using the Large Hadron Collider proton-proton collision dataset at a centre-of-mass energy of s√ = 13 TeV recorded by the ATLAS detector from 2015 to 2018, corresponding to an integrated luminosity of 139 fb−1. No significant excess above the Standard Model background is observed, and limits at 95% confidence level are set in the stop-neutralino mass plane and as a function of the mediator mass or the dark-matter particle mass. Stops are excluded up to 1200 GeV (710 GeV) in the two-body (three-body) decay scenario. In the four-body scenario stops up to 640 GeV are excluded for a stop-neutralino mass difference of 60 GeV. Scalar and pseudoscalar dark-matter mediators are excluded up to 200 GeV when the coupling strengths of the mediator to Standard Model and dark-matter particles are both equal to one and when the mass of the dark-matter particle is 1 GeV
Measurement Of Top Quark Antiquark Pair Production In Association With A Z Boson With A Trilepton Final State In Pp Collisions At 8 Tev Center Of Mass Energy
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Author : Ian Christopher MacNeill
language : en
Publisher:
Release Date : 2015
Measurement Of Top Quark Antiquark Pair Production In Association With A Z Boson With A Trilepton Final State In Pp Collisions At 8 Tev Center Of Mass Energy written by Ian Christopher MacNeill and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
A search for Z boson production with associated top-antitop pairs is performed with a final state which contains trileptons and b-tagged jets. The measurement is performed on the complete dataset of pp collisions at a center-of-mass energy of 8 TeV collected at the CMS detector, for a total instantaneous luminosity of 19.5 fb−1. A cross section is calculated for this final state and compared to the standard model prediction. The cross section for tt̄Z production is measured to be sigma=194+105/−89 fb. The measured cross section to theoretical cross section ratio is 0.94+0̇̇̇·51/−43. The process is measured with a significance of 2.33. This measurement is then combined with an outside 4 lepton channel measurement for an equivalent cross section measurement of sigma=200+90/−76 fb and a significance of 3.1.
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.
Associated Production Of A Top Quark And A Z Boson In Pp Collisions At S
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Author : Irina Antonela Cioară
language : en
Publisher:
Release Date : 2018
Associated Production Of A Top Quark And A Z Boson In Pp Collisions At S written by Irina Antonela Cioară and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.