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:
Total Pages: 0
Release: 2017
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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 Produced in Association with a Top Quark and Decaying Via H±{u2192}?? Using Pp Collision Data Recorded at

Search for Charged Higgs Bosons Produced in Association with a Top Quark and Decaying Via H±{u2192}?? Using Pp Collision Data Recorded at
Author:
Publisher:
Total Pages: 20
Release: 2016
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In this paper, charged Higgs bosons produced in association with a single top quark and decaying via H±→?? are searched for with the ATLAS experiment at the LHC, using proton–proton collision data at √s=13 TeV corresponding to an integrated luminosity of 3.2 fb-1. The final state is characterised by the presence of a hadronic ? decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidence-level upper limits on the production cross section times branching fraction, ?(pp→[b]tH±)×BR(H±→??) , between 1.9 pb and 15 fb, for charged Higgs boson masses ranging from 200 to 2000 GeV. Finally, the exclusion limits for this search surpass those obtained with the proton–proton collision data recorded at √s=8 TeV.

Search for Charged Higgs Bosons Produced in Association with a Top Quark and Decaying Via H±2!tau][nu] Using Pp Collision Data Recorded at [mml

Search for Charged Higgs Bosons Produced in Association with a Top Quark and Decaying Via H±2!tau][nu] Using Pp Collision Data Recorded at [mml
Author:
Publisher:
Total Pages: 20
Release: 2016
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In this paper, charged Higgs bosons produced in association with a single top quark and decaying via H±→[tau][nu] are searched for with the ATLAS experiment at the LHC, using proton-proton collision data at √s=13 TeV corresponding to an integrated luminosity of 3.2 fb-1. The final state is characterised by the presence of a hadronic [tau] decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidence-level upper limits on the production cross section times branching fraction, [sigma](pp→[b]tH±)×BR(H±→[tau][nu]) , between 1.9 pb and 15 fb, for charged Higgs boson masses ranging from 200 to 2000 GeV. Finally, the exclusion limits for this search surpass those obtained with the proton-proton collision data recorded at √s=8 TeV.

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:
Total Pages: 240
Release: 2019
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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.

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:
Total Pages:
Release: 2015
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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

A Search for Higgs Bosons in Final States with Multiple Tau Leptons at the DØ Experiment

A Search for Higgs Bosons in Final States with Multiple Tau Leptons at the DØ Experiment
Author:
Publisher:
Total Pages: 260
Release: 2012
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Two searches for the production of Higgs bosons decaying into [tau] and [mu] leptons, using data collected with the DØ detector at the Fermilab Tevatron p$\bar{p}$ collider, are presented. A search for the pair production of doubly charged Higgs bosons in the process q$\bar{q}$ 2!H++H--, where H ±± decays to [tau][tau], [mu][mu] or [tau][mu] lepton pairs, with an integrated luminosity of up to L = 7:0 fb-1, is presented. No signi cant excess of data over the expected SM background is observed and the results are used to set 95% C.L. limits on the pair production cross section of doubly charged Higgs bosons in the range 90

Search for a Charged Higgs Boson Produced in the Vector-boson Fusion Mode with Decay H± {u2192} W±Z Using pp Collisions at {u221A}s

Search for a Charged Higgs Boson Produced in the Vector-boson Fusion Mode with Decay H± {u2192} W±Z Using pp Collisions at {u221A}s
Author:
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Total Pages:
Release: 2015
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A search for a charged Higgs boson, H±, decaying to a W± boson and a Z boson is presented. The search is based on 20.3 fb–1 of proton-proton collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. The H± boson is assumed to be produced via vector-boson fusion and the decays W± → qq¯' and Z → e+e–/?+?– are considered. The search is performed in a range of charged Higgs boson masses from 200 to 1000 GeV. No evidence for the production of an H± boson is observed. Upper limits of 31–1020 fb at 95% C.L. are placed on the cross section for vector-boson fusion production of an H± boson times its branching fraction to W±Z. The limits are compared with predictions from the Georgi-Machacek Higgs triplet model.

Search for Higgs Bosons Decaying to aa in the ???? Final State in pp Collisions at {u221A}s

Search for Higgs Bosons Decaying to aa in the ???? Final State in pp Collisions at {u221A}s
Author:
Publisher:
Total Pages:
Release: 2015
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A search for the decay to a pair of new particles of either the 125 GeV Higgs boson (h) or a second charge parity (CP)-even Higgs boson (H) is presented. The data set corresponds to an integrated luminosity of 20.3 fb-1 of pp collisions at √s = 8 TeV recorded by the ATLAS experiment at the LHC in 2012. The search was done in the context of the next-to-minimal supersymmetric standard model, in which the new particles are the lightest neutral pseudoscalar Higgs bosons (a). One of the two a bosons is required to decay to two muons while the other is required to decay to two ? leptons. No significant excess is observed above the expected backgrounds in the dimuon invariant mass range from 3.7 to 50 GeV. Upper limits are placed on the production of h → aa relative to the standard model gg → h production, assuming no coupling of the a boson to quarks. The most stringent limit is placed at 3.5% for ma = 3.75 GeV. The upper limits are also placed on the production cross section of H → aa from 2.33 to 0.72 pb, for fixed ma = 5 GeV with mH ranging from 100 to 500 GeV.