Searches For Top Antitop Resonances In Proton Proton Collisions At A Center Of Mass Energy Of 7 Tev With The Atlas Detector
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Searches For Top Antitop Resonances In Proton Proton Collisions At A Center Of Mass Energy Of 7 Tev With The Atlas Detector
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Author : Jean-Raphael Lessard
language : en
Publisher:
Release Date : 2012
Searches For Top Antitop Resonances In Proton Proton Collisions At A Center Of Mass Energy Of 7 Tev With The Atlas Detector written by Jean-Raphael Lessard and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
The LHC and the ATLAS detector offer an unprecedented opportunity to test theories beyond the Standard Model of particle physics. Some of these theories predict heavy particles that would decay predominantly into a top and an antitop quark. This thesis presents a technique to experimentally measure the invariant mass (Mtt) of top-antitop pairs, event-by-event, allowing for a complete reconstruction of the Mtt spectrum. Two different models of heavy narrow resonances were considered: a particle X with a negligible mass width, and a Z' particle. Under these models, no resonances in the Mtt spectrum were found in 35.3 pb-1 of 7 TeV centre of mass proton-proton collision data. An upper limit on the production cross section times the branching ratio of the heavy particle decaying into a top-antitop (Sup) as a function of its mass (Mx or Mz) was established at a 95% confidence level. Including systematic errors, the observed (expected) Sup at 95% varies from 3.2 pb (27.9 +11.3 -19.9 pb) to 77.7 pb (9.8 +10.7 -5.6 pb) for Mx ranging from 760 GeV to 1000 GeV, and from 2.9 pb (55.9 +56.9 -47.0 pb) to 43.4 pb (7.8 +8.9 -4.7 pb) for Mz ranging from 700 GeV to 1000 GeV.
Search For New Phenomena In Top Antitop Quarks Final States With Additional Heavy Flavour Jets With The Atlas Detector
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Author : Daiki Yamaguchi
language : en
Publisher: Springer Nature
Release Date : 2019-10-30
Search For New Phenomena In Top Antitop Quarks Final States With Additional Heavy Flavour Jets With The Atlas Detector written by Daiki Yamaguchi and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-10-30 with Science categories.
This book reports on the search for a new heavy particle, the Vector-Like Top quark (VLT), in the Large Hadron Collider (LHC) at CERN. The signal process is the pair production of VLT decaying into a Higgs boson and top quark (TT→Ht+X, X=Ht, Wb, Zt). The signal events result in top–antitop quarks final states with additional heavy flavour jets. The book summarises the analysis of the data collected with the ATLAS detector in 2015 and 2016. In order to better differentiate between signals and backgrounds, exclusive taggers of top quark and Higgs boson were developed and optimised for VLT signals. These efforts improved the sensitivity by roughly 30%, compared to the previous analysis. The analysis outcomes yield the strongest constraints on parameter space in various BSM theoretical models. In addition, the book addresses detector operation and the evaluation of tracking performance. These efforts are essential to properly collecting dense events and improving the accuracy of the reconstructed objects that are used for particle identification. As such, they represent a valuable contribution to data analysis in extremely dense environments.
Qcd Radiation In Top Antitop And Z Jets Final States
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Author : Kiran Joshi
language : en
Publisher: Springer
Release Date : 2015-06-12
Qcd Radiation In Top Antitop And Z Jets Final States written by Kiran Joshi and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-06-12 with Science categories.
This thesis contains new research in both experimental and theoretical particle physics, making important contributions in each. Two analyses of collision data from the ATLAS experiment at the LHC are presented, as well as two phenomenological studies of heavy coloured resonances that could be produced at the LHC. The first data analysis was the measurement of top quark-antiquark production with a veto on additional jet activity. As the first detector-corrected measurement of jet activity in top-antitop events it played an important role in constraining the theoretical modelling, and ultimately reduced these uncertainties for ATLAS's other top-quark measurements by a factor of two. The second data analysis was the measurement of Z+2jet production and the observation of the electroweak vector boson fusion (VBF) component. As the first observation of VBF at a hadron collider, this measurement demonstrated new techniques to reliably extract VBF processes and paved the way for future VBF Higgs measurements. The first phenomenological study developed a new technique for identifying the colour of heavy resonances produced in proton-proton collisions. As a by-product of this study an unexpected and previously unnoticed correlation was discovered between the probability of correctly identifying a high-energy top and the colour structure of the event it was produced in. The second phenomenological study explored this relationship in more detail, and could have important consequences for the identification of new particles that decay to top quarks.
Search For Top Antitop Quark Resonances With The Atlas Detector At The Large Hadron Collider
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Author : Bertrand Chapleau
language : en
Publisher:
Release Date : 2014
Search For Top Antitop Quark Resonances With The Atlas Detector At The Large Hadron Collider written by Bertrand Chapleau 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.
"The intriguing nature of the top quark, by far the heaviest particle in the Standard Model of particle physics, has motivated the development of many theoretical extensions predicting the existence of new massive particles decaying to a pair of top-antitop quarks. The production of these hypothetical particles in proton-proton collisions at the Large Hadron Collider would reveal itself as a resonance in the expected smooth distribution of the top-antitop quark invariant mass. This thesis presents a search for such a new heavy particle decaying to a pair of top-antitop quarks in the semi-leptonic final state. The analyzed data sample amounts to a total of 4.6 fb-1 at a proton-proton collision center-of-mass energy of 7 TeV. Novel techniques specifically tailored to the identification of the decay products of highly energetic top quarks are developed and used. No evidence for resonant production of pairs of top-antitop quarks is found and, as a result, constraints are set on two theoretical models. Upper limits on the production cross-section times branching ratio are established at a 95% credibility level for a leptophobic Zʹ boson from the Topcolor model, and a Kaluza-Klein gluon from the Randall-Sundrum model. The Zʹ boson and the Kaluza-Klein gluon are excluded to exist (at a 95% credibility level) in the mass ranges 0.8-1.65 TeV and 0.8-1.88 TeV, respectively. The constraints de- rived in this thesis on the two theoretical models are more stringent than the ones obtained at other experiments, thanks to the large center-of-mass energy and the dedicated high-energy top quark identification techniques used." --
Measurement Of The Z T63 1hn T63 1hn Z Tau Tau Production Cross Section In Proton Proton Collisions At 7 Tev Center Of Mass Energy With The Atlas Detector
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Author : Daniele Capriotti
language : en
Publisher:
Release Date : 2012
Measurement Of The Z T63 1hn T63 1hn Z Tau Tau Production Cross Section In Proton Proton Collisions At 7 Tev Center Of Mass Energy With The Atlas Detector written by Daniele Capriotti and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Search For High Mass Resonances Decaying Into Electron Positron Pairs In Proton Proton Collisions At S
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Author : Christian Göringer
language : en
Publisher:
Release Date : 2013
Search For High Mass Resonances Decaying Into Electron Positron Pairs In Proton Proton Collisions At S written by Christian Göringer 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 Resonances In The Mass Distribution Of Jet Pairs With One Or Two Jets Identified As B Jets In Proton Proton Collisions At Mml
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Author :
language : en
Publisher:
Release Date : 2016
Search For Resonances In The Mass Distribution Of Jet Pairs With One Or Two Jets Identified As B Jets In Proton Proton Collisions At Mml 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.
In this paper, searches for high-mass resonances in the dijet invariant mass spectrum with one or two jets identified as b -jets are performed using an integrated luminosity of 3.2 fb-1 of proton-proton collisions with a centre-of-mass energy of √s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% credibility level, excited b* quarks with masses from 1.1 TeV to 2.1 TeV and leptophobic Z' bosons with masses from 1.1 TeV to 1.5 TeV. Finally, contributions of a Gaussian signal shape with effective cross sections ranging from approximately 0.4 to 0.001 pb are also excluded in the mass range 1.5-5.0 TeV.
Search For Dijet Resonances In Center Of Mass Energy
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Author : Sing Leung Cheung
language : en
Publisher:
Release Date : 2011
Search For Dijet Resonances In Center Of Mass Energy written by Sing Leung Cheung and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
A search for new heavy resonances in two-jet final states is described in this thesis. The data were collected by the ATLAS detector proton-proton collisions at s = 7 TeV and correspond to a time-integrated luminosity of 6.1 pb -1. The background-only hypothesis was tested on the observed data using BumpHunter test statistic. Consistency was found between the observed data and the background-only prediction. No resonant features were observed. A Bayesian approach using binned maximum likelihood was used to set upper limits on the product of cross section and detector acceptance for excited-quark (q*) production as a function of q* mass. At 95% credibility level (CL), the q* mass in the interval of 0.50 TeV
Search For High Mass States With One Lepton Plus Missing Transverse Momentum In Proton Proton Collisions At Sqrt S With The Atlas Detector
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Author :
language : en
Publisher:
Release Date : 2012
Search For High Mass States With One Lepton Plus Missing Transverse Momentum In Proton Proton Collisions At Sqrt S With The Atlas Detector written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
The ATLAS detector is used to search for high-mass states, such as heavy charged gauge bosons (W′,W*), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of ppcollisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 36 pb−1. No excess beyond standard model expectations is observed. A W′ with sequential standard model couplings is excluded at 95% confidence level for masses below 1.49 TeV, and a W* (charged chiral boson) for masses below 1.35 TeV.
Search For Resonances In The Mass Distribution Of Jet Pairs With One Or Two Jets Identified As B Jets In Proton U2013 Proton Collisions At
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Author :
language : en
Publisher:
Release Date : 2016
Search For Resonances In The Mass Distribution Of Jet Pairs With One Or Two Jets Identified As B Jets In Proton U2013 Proton Collisions At 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.
In this paper, searches for high-mass resonances in the dijet invariant mass spectrum with one or two jets identified as b -jets are performed using an integrated luminosity of 3.2 fb-1 of proton–proton collisions with a centre-of-mass energy of √s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% credibility level, excited b* quarks with masses from 1.1 TeV to 2.1 TeV and leptophobic Z' bosons with masses from 1.1 TeV to 1.5 TeV. Finally, contributions of a Gaussian signal shape with effective cross sections ranging from approximately 0.4 to 0.001 pb are also excluded in the mass range 1.5–5.0 TeV.