463 research outputs found
Study of the couplings between the Higgs boson and the electroweak gauge bosons in off-shell processes with the CMS experiment
No full textAbstract: The focus of this doctoral thesis is the experimental investigation of the couplings between the Brout-Englert-Higgs boson and the massive electroweak bosons (V). The analysis is performed on proton-proton collision data at 13 TeV collected by the CMS experiment during run 2 of the CERN LHC collider, which corresponds to about 140 fb-1 of integrated luminosity. The thesis mainly concentrates on the study of the production of highly virtual H bosons, known as "off-shell" (mH > 200 GeV), through gluon fusion and vector boson fusion production modes, followed by decay in the H->ZZ->l+l-nunu channel. The verification of an important prediction of the Standard Model of particle physics, namely the destructive interference of this process and the ZZ background, is achieved through the observation of events with an "off-shell" H boson. This interference ensures the unitarity of cross-section calculations. The H->ZZ->l+l-nunu channel offers a higher branching fraction rate (about 6 times higher) than the H->ZZ->l+l-l’+l’- channel and good sensitivity to the off-shell production process. The thesis provides evidence for the sought interference for the first time, with a significance level of 3.6 sigma, by analyzing the data from the H->ZZ->l+l-nunu channel and combining it with previously published results by the CMS collaboration in the H->ZZ->l+l-l’+l’- channel. Moreover, The high energy scale of the off-shell processes can constrain the presence of physics beyond the Standard Model in the H-V couplings, and an improvement of the constraints on anomalous H-V couplings of about 10% was achieved. Furthermore, the measurement of the off-shell production cross-section in the H->ZZ channel allows for the extraction of the total decay width of the H boson, which is proportional to the ratio between the off-shell cross-section and the on-shell cross-section measured in the H->ZZ->l+l-l’+l’- channel. This ratio is the only known method that can test the expected total width value within the framework of the Standard Model, 4.1 MeV. The total width was measured for the first time with an accuracy of about 50%, following the analysis and combination with measurements in the H->ZZ->l+l-l’+l’- channel, and the result is 3.2+2.4-1.7 MeV. The author of this thesis contributed to reducing two dominant sources of uncertainty in the analysis of the H->ZZ->l+l-nunu channel. The first is a theoretical uncertainty arising from the description of off-shell production processes, which was addressed by enabling the modeling of the signal and background that interfere in the off-shell region using event reweighting techniques. The second is experimental uncertainty arising from measurement errors in the tails of the missing transverse momentum distribution. This was reduced by optimizing event selection and rejection of the background constituted by the production of a Z boson accompanied by jets, and by testing the algorithms developed by the CMS collaboration to reduce the contribution of measurement errors in the tails of the missing transverse momentum distribution
Study of the couplings between the Higgs boson and the electroweak gauge bosons in off-shell processes with the CMS experiment
No full textThis Doctoral research project focuses on investigating the Higgs sector in the off-shell regime, specifically through vector boson fusion (VBF) and gluon fusion (GF) Higgs production processes that decay into ZZ particles with 2l2nu final states. The study utilizes data collected at the Large Hadron Collider (LHC) between 2016 and 2018, within the framework of the Standard Model (SM) and the SM Effective Field Theory (SMEFT) using HVV anomalous couplings. The project is part of the hzz2l2nu group.Within the hzz2l2nu group, the primary research objective is to measure the width of Higgs decays and investigate HVV anomalous couplings at a high mass scale (off-shell). This analysis aims to impose stringent constraints on HVV anomalous couplings and the Wilson coefficient of dimension-six operators by leveraging the sensitivity of Higgs to ZZ to 2l2nu processes.The analysis is conducted using data obtained from the CMS experiment during LHC run 2 at a center-of-mass energy of 13 TeV, with an integrated luminosity of approximately 140 fb-1. The main focus of the analysis revolves around two signal processes: VBF/GF Higgs production that decays into ZZ particles, which subsequently decay into two charged leptons (electrons or muons) and missing transverse energy. The off-shell regime is achieved by selecting events with an invariant transverse mass (mT) greater than 200 GeV, representing the final state system's mass. By considering both changes in the Higgs decay width and the presence of anomalous couplings, it becomes necessary to constrain both parameters simultaneously due to their impact on the off-shell cross-section.Although the signal channels exhibit sensitivity to the off-shell Higgs decay production cross-section, an analysis combining the off-shell study with the on-shell analysis of H→ ZZ→ four charged leptons are required to constrain the width accurately. The width is inferred from the ratio of off-shell to on-shell Higgs production cross sections.As part of this Doctoral research project, a matrix-element (MELA) reweighting tool has been developed to simulate samples with both SM couplings and anomalous couplings, utilizing high-mass Higgs fully-simulated samples available in the CMS experiment.The planned objectives for this research project are to measure the Higgs decay width with the highest precision achievable at the LHC and to impose strong constraints on HVV anomalous couplings and Wilson coefficients in SMEFT. The contribution to this analysis mainly involves studying various observables in anomalous coupling samples at NNLO QCD + NLO EWK achieved through MELA reweighting and k-factors corrections.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe
Study of the couplings between the Higgs boson and the electroweak gauge bosons in off-shell processes with the CMS experiment
No full textAbstract: This Doctoral research project focuses on investigating the Higgs sector in the off-shell regime, specifically through vector boson fusion (VBF) and gluon fusion (GF) Higgs production processes that decay into ZZ particles with 2l2nu final states. The study utilizes data collected at the Large Hadron Collider (LHC) between 2016 and 2018, within the framework of the Standard Model (SM) and the SM Effective Field Theory (SMEFT) using HVV anomalous couplings. The project is part of the hzz2l2nu group. Within the hzz2l2nu group, the primary research objective is to measure the width of Higgs decays and investigate HVV anomalous couplings at a high mass scale (off-shell). This analysis aims to impose stringent constraints on HVV anomalous couplings and the Wilson coefficient of dimension-six operators by leveraging the sensitivity of Higgs to ZZ to 2l2nu processes. The analysis is conducted using data obtained from the CMS experiment during LHC run 2 at a center-of-mass energy of 13 TeV, with an integrated luminosity of approximately 140 fb-1. The main focus of the analysis revolves around two signal processes: VBF/GF Higgs production that decays into ZZ particles, which subsequently decay into two charged leptons (electrons or muons) and missing transverse energy. The off-shell regime is achieved by selecting events with an invariant transverse mass (mT) greater than 200 GeV, representing the final state system's mass. By considering both changes in the Higgs decay width and the presence of anomalous couplings, it becomes necessary to constrain both parameters simultaneously due to their impact on the off-shell cross-section. Although the signal channels exhibit sensitivity to the off-shell Higgs decay production cross-section, an analysis combining the off-shell study with the on-shell analysis of H\u2192 ZZ\u2192 4l are required to constrain the width accurately. The width is inferred from the ratio of off-shell to on-shell Higgs production cross sections. As part of this Doctoral research project, a matrix-element (MELA) reweighting tool has been developed to simulate samples with both SM couplings and anomalous couplings, utilizing high-mass Higgs fully-simulated samples available in the CMS experiment. The planned objectives for this research project are to measure the Higgs decay width with the highest precision achievable at the LHC and to impose strong constraints on HVV anomalous couplings and Wilson coefficients in SMEFT. The contribution to this analysis mainly involves studying various observables in anomalous coupling samples at NNLO QCD + NLO EWK achieved through MELA reweighting and k-factors corrections
Analysis of b quark pair production signal from neutral 2HDM Higgs bosons at future linear colliders
No full textAbstract In this paper, the b quark pair production events are analyzed as a source of neutral Higgs bosons of the two Higgs doublet model type I at linear colliders. The production mechanism is e+e-→Z(∗)→HA→bb¯bb¯ assuming a fully hadronic final state. The analysis aim is to identify both CP-even and CP-odd Higgs bosons in different benchmark points accommodating moderate boson masses. Due to pair production of Higgs bosons, the analysis is most suitable for a linear collider operating at s=1 TeV. Results show that in selected benchmark points, signal peaks are observable in the b-jet pair invariant mass distributions at integrated luminosity of 500 fb-1
Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery (Nature, (2022), 607, 7917, (60-68), 10.1038/s41586-022-04892-x)
No full textCorrection to: Nature Published online 4 July 2022 In the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article.0info:eu-repo/semantics/publishe
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Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery
No full textCorrection to: Nature Published online 4 July 2022 In the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article
Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery
No full textIn the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the articl
Author Correction: A portrait of the Higgs boson by the CMS experiment ten years after the discovery (Nature, (2022), 607, 7917, (60-68), 10.1038/s41586-022-04892-x)
No full textCorrection to: Nature Published online 4 July 2022 In the version of this article initially published, CMS Collaboration author names, affiliations and acknowledgements were omitted and have now been included in the HTML and PDF versions of the article.SCOAP
Publisher Correction: Observation of triple J/ψ meson production in proton-proton collisions
No full textCorrection to: Nature Physics. Published online 19 January 2023. In the version of this article initially published, the first affiliation—Yerevan Physics Institute, Yerevan, Armenia—was missing from the list of author affiliations and has now been inserted in the HTML and PDF versions of the article.0CMS Collaborationinfo:eu-repo/semantics/publishe
Measurement of the Inclusive and Differential Higgs Boson Production Cross Sections in the Decay Mode to a Pair of τ Leptons in pp Collisions at √s = 13 TeV
No full textMeasurements of the inclusive and differential fiducial cross sections of the Higgs boson are presented, using the τ lepton decay channel. The differential cross sections are measured as functions of the Higgs boson transverse momentum, jet multiplicity, and transverse momentum of the leading jet in the event, if any. The analysis is performed using proton-proton collision data collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb-1. These are the first differential measurements of the Higgs boson cross section in the final state of two τ leptons. In final states with a large jet multiplicity or with a Lorentz-boosted Higgs boson, these measurements constitute a significant improvement over measurements performed in other final states.0CMS Collaborationinfo:eu-repo/semantics/publishe
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