A Search for Charged Higgs Bosons in Multilepton Final States and a Measurement of [p][p] to WZ to [l][v][l]'[l]' with the CMS Detector at the LHC
A Search for Charged Higgs Bosons in Multilepton Final States and a Measurement of [p][p] to WZ to [l][v][l]'[l]' with the CMS Detector at the LHC

Author: Devin Nathaniel Taylor

Publisher:

Published: 2017

Total Pages: 0

ISBN-13:

DOWNLOAD EBOOK

This thesis presents a search for a doubly-charged Higgs boson in three and four lepton final states. The two production modes considered are the associated production mode with a doubly-charged Higgs boson produced in association with a singly-charged Higgs boson and the pair production mode with the simultaneous production of two doubly-charged Higgs bosons. The search is performed with 12.9 fb-1 of square root s = 13 TeV proton-proton collision data collected with the Compact Muon Solenoid at the Large Hadron Collider. In addition, this thesis presents the first measurement of the WZ production cross section in proton-proton collisions at square root s = 13 TeV. The measurement is performed in the WZ to [l][v][l]'[l]' decay mode where [l], [l]' = e, [mu] with an integrated luminosity of 2.3 fb-1.

Search for Charged Higgs Bosons Decaying Via H± → Τ±ν in Fully Hadronic Final States with the ATLAS Detector at the LHC
Search for Charged Higgs Bosons Decaying Via H± → Τ±ν in Fully Hadronic Final States with the ATLAS Detector at the LHC

Author: Anna Kopp

Publisher:

Published: 2015

Total Pages:

ISBN-13:

DOWNLOAD EBOOK

Zusammenfassung: Searches for charged Higgs bosons decaying to a tau lepton and a neutrino in fully hadronic final states are presented in this thesis. The analyses are based on 4.6fb^-1 and 19.5fb^-1 of proton-proton collision data taken with the ATLAS detector at the LHC at center-of-mass energies of 7TeV and 8TeV in 2011 and 2012, respectively.Charged Higgs bosons with masses less than the top quark mass are searched for in events consistent with top-quark pair production and charged Higgs bosons with masses greater than the top quark mass are searched for in associated production with a top quark.In the search based on data taken in 2011, all background contributions are estimated in data-driven ways. Only a minor background contribution is estimated using simulation in the searches based on data taken in 2012; all dominant background contributions are estimated using data-driven methods here as well. An embedding method is used in all searches to assess the dominant and irreducible background contributions containing true hadronically decaying tau leptons and described in detail in this thesis.No significant excess of the data compared to the background expectations due to Standard Model processes is observed. Statistical analyses lead to 95% confidence-level upper limits on the branching ratios B(t->bH^±)xB(H^±->tau^± nu) between 0.23% and 1.3% for charged Higgs boson masses between 80GeV and 160GeV and on the production cross section times branching ratio, sigma(pp->tH^±+X)xB(H^±->tau^± nu) ranging from 0.76pb to 4.5fb for charged Higgs boson masses between 180GeV and 1000GeV. The branching ratio and cross section limits are used to derive constraints on the parameter space of minimal supersymmetric extensions of the Standard Model in various benchmark scenarios. These limits are the so far strictest limits set by the ATLAS collaboration in the search for charged Higgs bosons in fully hadronic final states

Search for Charged Higgs Bosons in Tau-lepton Final States with 139 Inverse Femtobarns of Proton-proton Collision Data Recorded at a Centre of Mass Energy of 13 TeV with the ATLAS Detector
Search for Charged Higgs Bosons in Tau-lepton Final States with 139 Inverse Femtobarns of Proton-proton Collision Data Recorded at a Centre of Mass Energy of 13 TeV with the ATLAS Detector

Author: Sina Bahrasemani

Publisher:

Published: 2019

Total Pages: 240

ISBN-13:

DOWNLOAD EBOOK

The Higgs boson, with a measured mass of approximately $125~GeV$, has been studied extensively since its discovery in 2012 at the Large Hadron Collider. This discovery opens the question of whether the Higgs boson of the Standard Model (SM) is the only scalar particle of Nature or it belongs to a larger scalar sector, as predicted in many Beyond the Standard Model (BSM) theories. Therefore, observation of charged Higgs bosons would indicate new physics. This thesis presents results of a search for a charged Higgs boson in the mass range $80~GeV$ to $3~TeV$, through tau-lepton final states. The search is performed using proton-proton collisions data at $\sqrt{s}=13~\mbox{TeV}$, collected with the ATLAS experiment, during 2015 to 2018. The final results are interpreted in the context of the Minimal SuperSymmetric Standard Model (MSSM) benchmark scenarios. In these scenarios, charged Higgs bosons coupling to tau-lepton are enhanced for some parts of the search phase space, thus increasing the chance of their discovery. No significant excess of events above the expected background from the Standard Model processes is observed. Therefore, upper limits on the charged Higgs boson production cross section times its branching ratio to tau-lepton and its associated neutrino are set at a 95\% Confidence Level. The results are also interpreted in the context of the hMSSM and $m^{mod -}_{h}$ benchmark scenarios of the MSSM. Due to the enhancement of the charged Higgs boson coupling to tau-leptons at high values of the $\tan\beta$ parameter of the MSSM, it is possible to exclude the high $\tan\beta$ region in the $M_{H^{\pm}}$--$\tan\beta$ parameter space. In this work, $\tan\beta$ values around 60 are excluded up to a charged Higgs boson mass of $1400~\GeV$. Furthermore, in the low mass region, below $170~GeV$, all values of $\tan\beta$ in range 1--60 are excluded at 95\% confidence level.