Search for a Vector-like Quark T' Decaying Into Top+Higgs in Single Production Mode in Full Hadronic Final State Using CMS Data Collected at 8 TeV

Search for a Vector-like Quark T' Decaying Into Top+Higgs in Single Production Mode in Full Hadronic Final State Using CMS Data Collected at 8 TeV
Author: José David Ruiz Alvarez
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Total Pages: 0
Release: 2015
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During 2012, the Large Hadron Collider (LHC) has delivered proton-proton collisions at 8 TeV center of mass energy to the ATLAS and CMS experiments. These two experiments have been designed to discover the Higgs boson and to search for new particles predicted by several theoretical models, as supersymmetry. The Higgs boson has been discovered by ATLAS and CMS experiments on July, 4th of 2012, starting a new era of discoveries in particle physics domain. With the confirmation of the existence of the Higgs boson, searches for new physics involving this boson are of major interest. In particular, data can be used to look for new massive particles that decay into the Higgs boson accompanied with other particles of the standard model. One expected signature is a Higgs boson produced with a top quark, the two heaviest particles in the standard model. The standard model predicts a cross section of top-Higgs production, then any enhancement of their associated production will be a clear signature of physics beyond the standard model. In addition, the existence of physics beyond the standard model can also be reflected by resonances that decay into a top-quark and a Higgs boson. In the first part of my work I describe the theoretical and experimental foundations of the standard model, as well as the experimental device. In the same theoretical chapter, I also discuss the formulation of an extension of the standard model. In addition, I describe a feasibility study of a search of one of the particles predicted by such model. The second part contains the realization of the search for a top partner, T_, within the CMS experiment. This top partner is a new particle very similar to the standard model top quark, but much heavier, that can decay into a top quark and a Higgs boson. The analysis looks for this particle in the full hadronic final state, where the Higgs boson decays into two b-quarks and the top quark decays into three standard model quarks, a b and two light quarks. In this channel, I reconstruct its mass from the identification of all its decay products. As a result of the analysis, I show the limits on the T_ production cross section from the number of observed events in the specific signature.

Search for Vector-like T Quarks Decaying to Top Quarks and Higgs Bosons in the All-hadronic Channel Using Jet Substructure

Search for Vector-like T Quarks Decaying to Top Quarks and Higgs Bosons in the All-hadronic Channel Using Jet Substructure
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Total Pages: 48
Release: 2015
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A search is performed for a vector-like heavy T quark that is produced in pairs and that decays to a top quark and a Higgs boson. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector in proton-proton collisions at √s = 8 TeV. For T quarks with large mass values the top quarks and Higgs bosons can have significant Lorentz boosts, so that their individual decay products often overlap and merge. Methods are applied to resolve the substructure of such merged jets. Upper limits on the production cross section of a T quark with mass between 500 and 1000 GeV/c2 are derived. If the T quark decays exclusively to tH, the observed (expected) lower limit on the mass of the T quark is 745 (773) GeV/c2 at 95% confidence level. For the first time an algorithm is used for tagging boosted Higgs bosons that is based on a combination of jet substructure information and b tagging.

Search for Single Production of a Heavy Vector-like T Quark Decaying to a Higgs Boson and a Top Quark with a Lepton and Jets in the Final State

Search for Single Production of a Heavy Vector-like T Quark Decaying to a Higgs Boson and a Top Quark with a Lepton and Jets in the Final State
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Release: 2016
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A search for single production of vector-like top quark partners (T) decaying into a Higgs boson and a top quark is performed using data from pp collisions at a centre-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The top quark decay includes an electron or a muon while the Higgs boson decays into a pair of b quarks. No significant excess over standard model backgrounds is observed. Exclusion limits on the product of the production cross section and the branching fraction are derived in the T quark mass range 700 to 1800 GeV. For a mass of 1000 GeV, values of the product of the production cross section and the branching fraction greater than 0.8 and 0.7 pb are excluded at 95% confidence level, assuming left- and right-handed coupling of the T quark to standard model particles, respectively. This is the first analysis setting exclusion limits on the cross section of singly produced vector-like T quarks at a centre-of-mass energy of 13 TeV.

Phenomena Beyond the Standard Model: What Do We Expect for New Physics to Look Like?

Phenomena Beyond the Standard Model: What Do We Expect for New Physics to Look Like?
Author: Roman Pasechnik
Publisher: Frontiers Media SA
Total Pages: 180
Release: 2020-09-03
Genre: Science
ISBN: 2889639908
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This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

A Search for Vector-like Quarks with the CMS Detector at the LHC

A Search for Vector-like Quarks with the CMS Detector at the LHC
Author: Reyer Edmond Band
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Total Pages: 0
Release: 2020
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A search for the pair-production of vector-like T and B quarks decaying into an all-hadronic final state is presented. Data corresponding to 35.9 fb−1 collected by CMS during 2016 at the LHC are analyzed. The analysis makes use of jet substructure and mass drop techniques to identify jets coming from boosted W decays, and is optimized for the discovery of a T quark decaying to a bottom quark and a W boson. The scalar sum of jet momenta is tested for the presence of signal, and upper limits at the 95% confidence level are established on the existence of the T and B for masses less than 1040 GeV and 1070 GeV respectively.