Evidence for a Higgs Boson in Tau Decays with the CMS Detector

Evidence for a Higgs Boson in Tau Decays with the CMS Detector
Author: Valentina Dutta
Publisher:
Total Pages: 185
Release: 2014
Genre:
ISBN:

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In this thesis, I describe the search for a Higgs boson through its decay to a pair of tan leptons with the tau-pair subsequently decaying to ail electron, a muon, and neutrinos. The search is performed using data collected from proton-proton collisions by the Compact Muon Solenoid experiment at the Large Hadron Collider, corresponding to 5.0 fb-1 of integrated luminosity recorded at a center-of-mass energy of 7 TeV and 19.7 fb-1 at 8 TeV. The expected significance for a Standard Model Higgs boson signal with a mass of 125 GeV is at the level of 1.2 standard deviations for the electron muon tau-pair decay mode. A mild excess of events is seen above the SM background expectation in this decay mode, consistent with a SM Higgs boson of mass 125 GeV. In combination with results using other tau-pair decay modes, an excess of events above the background expectation is seen at the level of 3.4 standard deviations. This constitutes the first evidence for a Higgs boson to decay to leptons. This thesis also describes an analysis of the data in the context of physics beyond the Standard Model, particularly in the framework of its Minimal Supersymnnetric extension.

Electroweak Physics and Evidence for a Higgs Boson Decaying to a Pair of Tau Leptons with the CMS Detector

Electroweak Physics and Evidence for a Higgs Boson Decaying to a Pair of Tau Leptons with the CMS Detector
Author: Aram Apyan
Publisher:
Total Pages: 170
Release: 2017
Genre:
ISBN:

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.Studies of the electroweak interactions using final states with leptons in proton-proton collisions at the Large Hadron Collider at [square root of] s = 7 TeV, [square root of] s = 8 TeV, and [square root of] s = 13 TeV center-of-mass energies are described. Measurements of total inclusive and fiducial W and Z boson production cross sections and their ratios are performed. The W and Z bosons are observed via their decays to electrons and muons. An indirect determination of the total width of the W boson and the B(W --> lv) from the measured cross section ratios is described. The discovery of a new boson with a mass of 125 GeV at the Large Hadron Collider in 2012 sheds a new light on understanding the nature of electroweak symmetry breaking. A question of great significance is whether the new field couples to fermions through a Yukawa coupling interaction predicted in the standard model of particles. Evidence of the 125 GeV Higgs boson decay to a pair of tau leptons with an observed significance of 3.1 standard deviations is established. The nature of the Higgs sector is probed through searches for neutral resonances decaying to a pair of tau leptons in gluon-fusion and b-quark associated production modes with no observation of a significant excess. In addition, the feasibility of measuring the standard model Higgs boson self-coupling with an expected data sample corresponding to an integrated luminosity of 3000 fb-1 is studied.

A Study of the Standard Model Higgs Boson Decaying to a Pair of Tau Leptons with the CMS Detector at the LHC

A Study of the Standard Model Higgs Boson Decaying to a Pair of Tau Leptons with the CMS Detector at the LHC
Author: Tyler Henry Ruggles
Publisher:
Total Pages: 0
Release: 2018
Genre:
ISBN:

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This thesis presents a 5.5 standard deviation observation of the Higgs boson decaying to fermions using the data collected at the LHC at 13 TeV center-of-mass energy. The studied dataset corresponds to an integrated luminosity of 35.9 inverse femtobarns. The best fit signal strength for the H to tau tau process is measured to be mu = 1.24 ^{+0.29}/{-0.27}, consistent with standard model predictions. Unique event categories are used targeting the leading Higgs boson production processes, gluon fusion, vector boson fusion, and associated production. This provides signal regions sensitive to Higgs boson couplings to both fermions and vector bosons. These two Higgs boson couplings are measured and are consistent with standard model predictions within one standard deviation. This 5.5 standard deviation observation of the H to tau tau process and the consistency of the Higgs boson couplings with the standard model provide confirmation of the Higgs boson Yukawa couplings to fermions. This is evidence that the Higgs field provides mass for the tau lepton in addition to the vector bosons.

Scalar Boson Decays to Tau Leptons

Scalar Boson Decays to Tau Leptons
Author: Cécile Caillol
Publisher: Springer
Total Pages: 282
Release: 2017-11-15
Genre: Science
ISBN: 3319706500

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This thesis presents a study of the scalar sector in the standard model (SM), as well as various searches for an extended scalar sector in theories beyond the SM (BSM). The first part of the thesis details the search for an SM Higgs boson decaying to taus, and produced by gluon fusion, vector boson fusion, or associated production with a vector boson, leading to evidence for decays of the Higgs boson to taus. In turn, the second part highlights several searches for an extended scalar sector, with scalar boson decays to taus. In all of the analyses presented, at least one scalar boson decays to a pair of taus. The results draw on data collected by the Compact Muon Solenoid (CMS) detector during proton–proton collisions with a center-of-mass energy of 7 or 8 TeV.

Measurement of the Higgs Boson Properties Using Its Decay to a Pair of [tau] Leptons in Proton-proton Collisions at √s

Measurement of the Higgs Boson Properties Using Its Decay to a Pair of [tau] Leptons in Proton-proton Collisions at √s
Author: Doyeong Kim
Publisher:
Total Pages: 0
Release: 2022
Genre:
ISBN:

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The Compact Muon Solenoid (CMS) detector has successfully operated with the Large Hadron Collider (LHC) collisions since 2010, leading to the Higgs boson discovery in 2012 by the CMS and ATLAS collaborations. The analyses of data taken during Run 2 (2016-2018) has already led to many interesting results about the properties of the Higgs boson and for the most part they are compatible in the context of the standard model (SM) so far. These studies are important because the SM appears to be an approximation of a more general theory. Precise studies of the Higgs boson's interactions with the known matter and force particles are essential to reveal the microscopic deviations from the SM prediction. One of such interactions is Yukawa couplings of the Higgs boson and fermions. The H → [tau tau] decay is the most sensitive fermionic decay mode that allows direct probing of this interaction. This thesis presents a study of the Higgs boson properties by observing its decay to a pair of tau leptons and testing evidence of non-SM interactions in the Higgs boson production. The results exploit the data collected by the CMS detector during LHC Run-2, in proton-proton collisions with a center-of-mass energy of 13 TeV. Firstly, the Higgs bosons' properties were explored by two complementary approaches by measuring its cross sections. Thanks to the observation of the H → [tau tau] decay in 2016, we can measure the total cross section with higher precision. Furthermore, in the first analysis, the cross sections of different Higgs productions were scrutinized using fine selections within each Higgs production mode which are mutually exclusive using the Simplified Template Cross Section (STXS) framework, proposed by the LHC Higgs Cross Section Working Group. In the second analysis, the first-ever measurement of the inclusive and differential fiducial cross sections for the Higgs boson production decaying to a pair of tau leptons was presented. In the third analysis, a search for anomalous couplings in the Higgs production vertex, including Charge-Parity (CP) violating couplings, is also performed targeting Higgs boson production via gluon fusion in association with two jets and vector boson fusion. None of these analyses has found any hint of new physics beyond the SM, but stringent limits on anomalous Higgs boson couplings to data were set and cross sections of the Higgs bosons in smaller phase spaces were precisely measured.

Search for Dark Matter Recoiling from a Higgs Boson, which Decays to Tau Lepton Pairs, with the CMS Detector at the LHC

Search for Dark Matter Recoiling from a Higgs Boson, which Decays to Tau Lepton Pairs, with the CMS Detector at the LHC
Author: Jithin Madhusudanan Sreekala
Publisher:
Total Pages: 0
Release: 2022
Genre:
ISBN:

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This thesis describes search for dark matter particles recoiling from a Higgs boson at the CMS detector at the LHC where the Higgs subsequently decays to two tau leptons. The analysis uses 2017 and 2018 RUN II dataset collected by CMS experiment. This thesis discusses two scenarios, one where taus are resolved and one where taus are boosted.

Observation of Standard Model Higgs Boson Decays to Tau Leptons and a Search for Dark Matter with the CMS Detector at the LHC

Observation of Standard Model Higgs Boson Decays to Tau Leptons and a Search for Dark Matter with the CMS Detector at the LHC
Author: Laura Margaret Dodd
Publisher:
Total Pages: 0
Release: 2018
Genre:
ISBN:

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A search for the standard model (SM) Higgs boson which decays to a pair of [tau] leptons is presented in this thesis using 35.9 f b−1 of 13 TeV data collected in 2016 by the CMS detector at CERN. The final states considered require that (1) one [tau] lepton decays leptonically while the other decays hadronically ([mu][tau]h or e[tau]h), (2) both taus decay hadronically ([tau]h[tau]h) or (3) one tau lepton decays to an electron while the other decays to a muon (e[mu]). This thesis specifically focuses on the details of the semi-hadronic decay channels ([mu][tau]h and e[tau]h), and presents the results of all channels combined. The signal strength, [mu], relative to the expectation for the SM Higgs boson is measured to be [mu] = 1.09+0.27−0.24. An excess is observed (expected) corresponding to 4.9 (4.7) [sigma] using 2016 data. The observed (expected) significance reaches 5.9 (5.9) [sigma] when combined with 7 and 8 TeV data collected at CMS. Subsequently following the SM search, a search for dark matter (DM) is presented and interpreted in two simplified Higgs-portal models: a baryonic dark matter model and a two Higgs-doublet model. In this thesis, the Higgs boson is required to decay to an opposite- sign tau pair. The tau pair final states considered are e[tau]h, [mu][tau]h, and [tau]h[tau]h. The expected 95% confidence level upper limits are produced and compared with the observed limit. No significant deviations beyond the SM prediction are observed.

Search for the Higgs Boson in Its Decay Into Tau Leptons at CMS

Search for the Higgs Boson in Its Decay Into Tau Leptons at CMS
Author: Matthew Hans Chan
Publisher:
Total Pages: 204
Release: 2013
Genre:
ISBN:

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A search for the Standard Model Higgs boson in the H --> rr channel is presented. The search is performed on proton collision data collected by the Compact Muon Solenoid at the Large Hadron Collider. The data corresponds to 4.9 fb-1 of proton collisions at [square root of]s = 7 TeV and 19.5 fb-1 at [square root of]s = 8 TeV. The search is based on di-tau events in which one tau decays into an electron or muon, and the other tau decays into hadrons. The search focuses on Higgs masses between 110 GeV and 145 GeV. The analysis reveals no statistically significant excess in the data over the Standard Model backgrounds. Upper limits on the Higgs production cross section at the 95% confidence level are established. The observed limit is statistically consistent with the expected limit in the background-only hypothesis but does not exclude any Higgs mass.