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10h
Romain MADAR
"H->tautau search in ATLAS"
The search for H->tautau process is crucial to identify the new boson as the relic particle of the electroweak symmetry breaking, the Higgs boson. Indeed, this channel can provide, together with the H->bb process, a direct access to the coupling strength between the Higgs field and two elementary fermions and therefore test the proportionality between mass and coupling in the fermionic sector. In this seminar, an overview of the H->tautau search in collisions recorded by the ATLAS detector where only one tau decays hadronically will be presented. The following chosen aspects of the analysis will be emphasized : event selections optimization, background estimation, challenge of the di-tau mass reconstruction (due to escaping neutrinos), and statistical extraction of the result. Finally, the experimental sensitivity reached in this channel will be discussed in term of exclusion limit and significance of the signal.
The discovery of a new Higss-like boson with mass ~ 125 to 126 GeV, announced by both ATLAS and CMS collaborations, is the culmination of the hunt for the elusive Higgs boson and signals a new era in the field of particle physics. The new particle was observed primarily to its decay through the two Z bosons channel (where the Z bosons decay to pairs of electrons or muons (H -> ZZ(*) -> 4l) and the two photons channel (H ->gg ). The updated H -> ZZ(*) -> 4` using the full dataset collected by the ATLAS collaboration during 2011 and 2012 is presented. The data also allow for a first measurement of the properties of this new Higgs like boson (mass, couplings, Spin/Parity) , using the H->ZZ(*)->4l channel.
14h
Elisabeth PETIT
"Newly discovered Higgs-like boson with the ATLAS detector : production modes and couplings"
The discovery of a boson in the mass region of 126 GeV in the search for the Standard Model Higgs boson by the ATLAS and CMS collaborations at the LHC was one of the greatest achievement in particle physics over the last decade. However the detailed consistency of the properties of this new particle with the expectation for the SM Higgs boson still needed to be assessed. The measured mass, around 126 GeV, allows to study this boson in several decay channels. With the data recorded by the ATLAS detector in 2011 and 2012, it is also possible to distinguish between several production modes. Since the couplings of the Higgs boson to the fermions and bosons determines the production cross-section and partial branching ratios, the studies of those production and decay modes allows us to have a first estimate of those couplings.
Olivier ARNAEZ
"Résultats récents de l'expérience ATLAS concernant la recherche du boson de Higgs dans le canal H->WW"
La recherche du boson de Higgs, indispensable à la validation du Modèle Standard, est un des éléments centraux du programme de physique au LHC. Dans ce contexte, le canal H --> WW a contribué à établir la présence d'un nouveau boson ayant une masse proche de 125 GeV, ceci grâce à son grand rapport d'embranchement et de la clarté de sa signature. Il a fallu optimiser l'efficacité des coupures de sélection et étudier de manière précise les échantillons de contrôle des fonds (continuum WW, top et W+jets principalement) pour permettre l'observation de cette nouvelle particule. J'exposerai ainsi le résultat de ces analyses dans la collaboration ATLAS.
Cecile DETERRE
"Top charge asymmetry and polarization measurements in ATLAS"
Precision measurements of the top quark properties are possible at the LHC because of the large statistics available. We are interested here in the top charge asymmetry, which is an effect predicted at next-to leading order in QCD, and which can be sensitive to the presence of new physics. The measurements at the Tevatron show an asymmetry about 2 standard deviations larger than the Standard Model predictions, and theorists have developed models of physics beyond the Standard which could explain this asymmetry. Most of these models also predict an asymmetry at the LHC and a polarization of the top different than the Standard Model predictions. I will show the latest results of ATLAS for these two measurements.
Romain MADAR
"H->tautau search in ATLAS"
The search for H->tautau process is crucial to identify the new boson as the relic particle of the electroweak symmetry breaking, the Higgs boson. Indeed, this channel can provide, together with the H->bb process, a direct access to the coupling strength between the Higgs field and two elementary fermions and therefore test the proportionality between mass and coupling in the fermionic sector. In this seminar, an overview of the H->tautau search in collisions recorded by the ATLAS detector where only one tau decays hadronically will be presented. The following chosen aspects of the analysis will be emphasized : event selections optimization, background estimation, challenge of the di-tau mass reconstruction (due to escaping neutrinos), and statistical extraction of the result. Finally, the experimental sensitivity reached in this channel will be discussed in term of exclusion limit and significance of the signal.
Somnath CHOUDHURY "Higgs Boson search in Tau Pair decay mode at CMS" A search for the Standard Model Higgs Boson decaying to Tau Pairs has been performed using proton-proton collision events recorded by the CMS experiment at the LHC in 2011 and 2012 at center-of-mass energies of 7 and 8 TeV respectively. The analysis exploits the gluon-gluon fusion and vector boson fusion production mechanisms. The tau pair signature in five different final states involving fully leptonic, semi-leptonic and fully hadronic decay modes have been presented. An excess is observed over a broad mass range compatible with the presence of the Higgs Boson discovered at around 125 GeV. In addition, a search has been reported for neutral Higgs Bosons in the Minimal Supersymmetric extension of the Standard Model (MSSM) with decays to tau lepton pairs. To enhance the sensitivity to neutral MSSM Higgs Bosons, the search includes the case where the Higgs Boson is produced in association with a b-quark jet. No excess has been observed in the tau-pair invariant-mass spectrum and exclusion limits have been set in the MSSM parameter space within the maximal mixing scenario of the stop-top sector.. Christos ANASTOPOULOS "Updated results and measurement of the properties of the Higgs-like boson in the H->ZZ->4l leptons channel"
The discovery of a new Higss-like boson with mass ~ 125 to 126 GeV, announced by both ATLAS and CMS collaborations, is the culmination of the hunt for the elusive Higgs boson and signals a new era in the field of particle physics. The new particle was observed primarily to its decay through the two Z bosons channel (where the Z bosons decay to pairs of electrons or muons (H -> ZZ(*) -> 4l) and the two photons channel (H ->gg ). The updated H -> ZZ(*) -> 4` using the full dataset collected by the ATLAS collaboration during 2011 and 2012 is presented. The data also allow for a first measurement of the properties of this new Higgs like boson (mass, couplings, Spin/Parity) , using the H->ZZ(*)->4l channel.
14h
Elisabeth PETIT
"Newly discovered Higgs-like boson with the ATLAS detector : production modes and couplings"
The discovery of a boson in the mass region of 126 GeV in the search for the Standard Model Higgs boson by the ATLAS and CMS collaborations at the LHC was one of the greatest achievement in particle physics over the last decade. However the detailed consistency of the properties of this new particle with the expectation for the SM Higgs boson still needed to be assessed. The measured mass, around 126 GeV, allows to study this boson in several decay channels. With the data recorded by the ATLAS detector in 2011 and 2012, it is also possible to distinguish between several production modes. Since the couplings of the Higgs boson to the fermions and bosons determines the production cross-section and partial branching ratios, the studies of those production and decay modes allows us to have a first estimate of those couplings.
Olivier ARNAEZ
"Résultats récents de l'expérience ATLAS concernant la recherche du boson de Higgs dans le canal H->WW"
La recherche du boson de Higgs, indispensable à la validation du Modèle Standard, est un des éléments centraux du programme de physique au LHC. Dans ce contexte, le canal H --> WW a contribué à établir la présence d'un nouveau boson ayant une masse proche de 125 GeV, ceci grâce à son grand rapport d'embranchement et de la clarté de sa signature. Il a fallu optimiser l'efficacité des coupures de sélection et étudier de manière précise les échantillons de contrôle des fonds (continuum WW, top et W+jets principalement) pour permettre l'observation de cette nouvelle particule. J'exposerai ainsi le résultat de ces analyses dans la collaboration ATLAS.
Cecile DETERRE
"Top charge asymmetry and polarization measurements in ATLAS"
Precision measurements of the top quark properties are possible at the LHC because of the large statistics available. We are interested here in the top charge asymmetry, which is an effect predicted at next-to leading order in QCD, and which can be sensitive to the presence of new physics. The measurements at the Tevatron show an asymmetry about 2 standard deviations larger than the Standard Model predictions, and theorists have developed models of physics beyond the Standard which could explain this asymmetry. Most of these models also predict an asymmetry at the LHC and a polarization of the top different than the Standard Model predictions. I will show the latest results of ATLAS for these two measurements.
