Global ETD Search

1	Search for the W ± W ± W ∓ production and the doubly charged higgs with the Atlas detector / Recherche de la production www et du higgs doublement chargé avec le détecteur Atlas Zhang, Ruiqi 01 December 2017 (has links) L’expérience ATLAS (A Toroidal LHC Apparatus), collaboration de plus de 3000 scientifiques dans le monde, mène des recherches auprès du grand collisionneur de hadron (LHC). Celui-ci a produit des collisions de faisceaux de protons à une énergie dans le centre de masse de 7 TeV en 2011 et 8 TeV en 2012, période appelée Run1 et représentant 20.3 fb−1 de luminosité intégrée, puis en 2015 et 2016 à 13 TeV pour le Run 2 avec 36.1 fb−1. Le détecteur généraliste ATLAS a un riche potentiel de mesures précises du Modèle Standard (SM) et de recherche de phénomènes de nouvel physique. Deux analyses de physiques sont ici présentées. La première consiste à rechercher dans les données Run 1 la production de tri-bosons, W±W±W∓, se désintégrant totalement ou partiellement en leptons et à étudier le couplage de jauge quartique anormal (aQGC). Le nombre d’événements observés est en accord avec les prédictions du SM. La limite supérieure observée à 95% CL sur la section efficace W±W±W∓ SM est de 730 fb avec une limite attendue de 560 fb en l’absence de production W±W±W∓. La deuxième analyse présentée est la recherche du boson de Higgs doublement chargé effectuée sur les données du Run 2. Ce boson est prédit par un modèle qui prolonge le SM pour permettre des neutrinos massif. Ce modèle introduit plusieurs bosons de Higgs dont l'un est le H±±. Le cas où ce dernier se désintègre en bosons W avec un état final à deux leptons de même charge est plus particulièrement étudié. Le bruit de fond total estimé est en accord avec les données et aucun excès significatif n’est observé. Des limites supérieures sont déduites et le modèle considéré est exclus à 95% CL pour MH±± < 220 GeV. / The ATLAS (A Toroidal LHC Apparatus) experiment, a collaboration of more than 3,000 scientists worldwide, is conducting research at the Large Hadron Collider (LHC). It produced proton beam collisions at an energy in the center of mass of 7 TeV in 2011 and 8 TeV in 2012, period called Run1 and representing 20.3 fb-1 of integrated luminosity, then in 2015 and 2016 at 13 TeV for Run 2 with 36.1 fb-1. The ATLAS general purpose detector has a rich potential for accurate Standard Model (SM) measurements and the search for new physics phenomena. Two physics analyzes are presented here. The first is to search the Run 1 data for tri-bosons production, W ± W ± W∓, totally or partially decayed into leptons and to study abnormal quartic gauge coupling (aQGC). The number of observed events is consistent with the SM predictions. The observed upper limit at 95% CL on the W ± W ± W∓ SM cross section is 730 fb with an expected limit of 560 fb in the absence of W ± W ± W∓ production. The second analysis presented is the search for the doubly charged Higgs boson carried out on the Run 2 data. This boson is predicted by a model that extends the SM to allow massive neutrinos. This model introduces several Higgs bosons, one of which is the H ±±. The case where this latter decays in bosons W with a final state with two leptons of the same charge is more particularly studied. The estimated total background is in agreement with the data and no significant excess is observed. Upper limits are deduced and the model considered is excluded at 95% CL for MH ±± <220 GeV. Lhc Atlas Www Higgs doublement chargé Aqgc Lhc Atlas Www Doubly charged higgs Aqgc 539
2	Probing Electroweak Gauge Boson Scattering with the ATLAS Detector at the Large Hadron Collider Anger, Philipp 07 October 2014 (has links) (PDF) Electroweak gauge bosons as central components of the Standard Model of particle physics are well understood theoretically and have been studied with high precision at past and present collider experiments. The electroweak theory predicts the existence of a scattering process of these particles consisting of contributions from triple and quartic bosonic couplings as well as Higgs boson mediated interactions. These contributions are not separable in a gauge invariant way and are only unitarized in the case of a Higgs boson as it is described by the Standard Model. The process is tied to the electroweak symmetry breaking which introduces the longitudinal modes for the massive electroweak gauge bosons. A study of this interaction is also a direct verification of the local gauge symmetry as one of the fundamental axioms of the Standard Model. With the start of the Large Hadron Collider and after collecting proton-proton collision data with an integrated luminosity of 20.3/fb at a center-of-mass energy of 8 TeV with the ATLAS detector, first-ever evidence for this process could be achieved in the context of this work. A study of leptonically decaying WWjj, same-electric-charge diboson production in association with two jets resulted in an observation of the electroweak WWjj production with same electric charge of the W bosons, inseparably comprising WW->WW electroweak gauge boson scattering contributions, with a significance of 3.6 standard deviations. The measured production cross section is in agreement with the Standard Model prediction. In the course of a study for leptonically decaying WZ productions, methods for background estimation, the extraction of systematic uncertainties and cross section measurements were developed. They were extended and applied to the WZjj final state whereof the purely electroweakly mediated contribution is intrinsically tied to the scattering of all Standard Model electroweak gauge bosons: Wγ->WZ and WZ->WZ. Three charged leptons and a neutrino from the decay of the final state bosons allow inferences about the scattering process. A distinct signature is provided by the two accompanying tagging jets as remnants of the incoming quarks radiating the initial electroweak gauge bosons. The cross section of the electroweak WZjj production was measured to σ(fiducial, observed) = (0.63 +0.32 -0.28 (stat.) +0.41 -0.24 (syst.)) fb and was found to be consistent with the Standard Model prediction at next-to-leading order in perturbative quantum chromodynamics, σ(fiducial, theory) = (0.31 +0.03 -0.05) fb. Unfolded differential cross sections of kinematic variables sensitive to models of new physics were derived. Anomalous quartic electroweak gauge couplings are introduced as dimensionless coupling parameters of additional operators within an effective field theory approach. Constraints on the parameters of operators with dimension eight were set employing a unitarization prescription based on form factors. CERN LHC ATLAS 2014 Standardmodell Teilchenphysik Elementarteilchenphysik VBS Eichboson-Streuung Vektorboson-Streuung Vektor-Boson-Streuung aQGC aqgc anomale Eichkopplung anomale Vierer-Eichboson-Kopplung Effektive Lagrangedichte Vierer-Vertex Vierer-Eichboson-Vertex Higgs WZ-Endzustand Sherpa VBFNLO Whizard K-Matrix Form-Faktor Formfaktor Unitarisierung Boson CERN LHC ATLAS 2014 Standard Model Particle Physics VBS Vector Boson Scattering Vector-Boson-Scattering Vector-Boson Scattering Gauge Boson Scattering Electroweak Gauge Boson Scattering aQGC aqgc Anomalous Quartic Gauge Boson Coupling Anomalous Gauge Boson Coupling Effective Lagrangian Quartic Vertex Quartic Gauge Boson Vertex Higgs WZ Final State Sherpa VBFNLO Whizard K-Matrix Form-Factor Unitarization Unitarisation Boson ddc:530 rvk:UO 6420 CERN LHC 2014 Elementarteilchenphysik Boson
3	Probing Electroweak Gauge Boson Scattering with the ATLAS Detector at the Large Hadron Collider Anger, Philipp 01 September 2014 (has links) Electroweak gauge bosons as central components of the Standard Model of particle physics are well understood theoretically and have been studied with high precision at past and present collider experiments. The electroweak theory predicts the existence of a scattering process of these particles consisting of contributions from triple and quartic bosonic couplings as well as Higgs boson mediated interactions. These contributions are not separable in a gauge invariant way and are only unitarized in the case of a Higgs boson as it is described by the Standard Model. The process is tied to the electroweak symmetry breaking which introduces the longitudinal modes for the massive electroweak gauge bosons. A study of this interaction is also a direct verification of the local gauge symmetry as one of the fundamental axioms of the Standard Model. With the start of the Large Hadron Collider and after collecting proton-proton collision data with an integrated luminosity of 20.3/fb at a center-of-mass energy of 8 TeV with the ATLAS detector, first-ever evidence for this process could be achieved in the context of this work. A study of leptonically decaying WWjj, same-electric-charge diboson production in association with two jets resulted in an observation of the electroweak WWjj production with same electric charge of the W bosons, inseparably comprising WW->WW electroweak gauge boson scattering contributions, with a significance of 3.6 standard deviations. The measured production cross section is in agreement with the Standard Model prediction. In the course of a study for leptonically decaying WZ productions, methods for background estimation, the extraction of systematic uncertainties and cross section measurements were developed. They were extended and applied to the WZjj final state whereof the purely electroweakly mediated contribution is intrinsically tied to the scattering of all Standard Model electroweak gauge bosons: Wγ->WZ and WZ->WZ. Three charged leptons and a neutrino from the decay of the final state bosons allow inferences about the scattering process. A distinct signature is provided by the two accompanying tagging jets as remnants of the incoming quarks radiating the initial electroweak gauge bosons. The cross section of the electroweak WZjj production was measured to σ(fiducial, observed) = (0.63 +0.32 -0.28 (stat.) +0.41 -0.24 (syst.)) fb and was found to be consistent with the Standard Model prediction at next-to-leading order in perturbative quantum chromodynamics, σ(fiducial, theory) = (0.31 +0.03 -0.05) fb. Unfolded differential cross sections of kinematic variables sensitive to models of new physics were derived. Anomalous quartic electroweak gauge couplings are introduced as dimensionless coupling parameters of additional operators within an effective field theory approach. Constraints on the parameters of operators with dimension eight were set employing a unitarization prescription based on form factors. info:eu-repo/classification/ddc/530 ddc:530

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