9 research outputs found

    The CALICE AHCAL: a highly granular SiPM-on-tile hadron calorimeter prototype

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    The Analogue Hadron Calorimeter (AHCal) of the CALICE collaboration is a technological prototype for future linear collider detectors, addressing scalability, integration and engineering challenges imposed by the experimental environment. It is based on the SiPM-on-tile technology, where the active layers of the calorimeter are formed by 3 × 3 cm2^{2} plastic scintillator tiles placed on top of SiPMs mounted on readout boards that also house SPIROC-2E front-end ASICs. A large prototype with 22 000 channels has been constructed using techniques suitable for mass production and automatic assembly. The calorimeter successfully took muon, electron and pion data at the CERN-SPS. Smaller setups for dedicated measurements were also tested later at the DESY-II facility. Main features of the alternative KlauS ASIC and megatile scintillator designs are also presented

    Intercalibration des couches du calorimètre électromagnétique d'ATLAS et mesure de couplages CP impairs du boson de Higgs dans son canal de désintégration en quatre leptons avec les données du Run 2 au LHC

    No full text
    After the Higgs boson discovery at the LHC in 2012, interest turned to Higgs boson property measurements to refine the tests of the Standard Model and probe for new physics. One of its key properties is its spin-parity (CP), predicted to be 0+ in the Standard Model. Analyses of data collected during the Run 1 of the LHC rejected all pure spin-parity (CP) state other than 0+. However mixed CP states are still possible, and would indicate CP violation in the Higgs sector.The first part of this thesis focuses on the ATLAS electromagnetic calorimeter calibration, needed to reach a permil level on electron and photon energy resolution which are of prime importance for Higgs boson studies. One step of the calibration sequence consists of the layer intercalibration of the electromagnetic calorimeter, needed to correct residual electronics miscalibration and cross-talk effects. The Run 1 method has proven to be unreliable for the pileup levels in Run 2 and a new method was developed, ensuring a precise control on the systematic uncertainties.The second part of this thesis puts emphasis on the Higgs boson to vector boson CP-odd couplings, with the Higgs boson decaying to four leptons. This channel, despite low statistics, provides a clean signature and a signal-to-noise ratio over two, allowing for a precise determination of the Higgs boson properties. The vector boson fusion production channel offers the best sensitivity to CP effects thanks to its two characteristic tagging jets in the final state. The contamination from the gluon fusion production mode with additional jets is reduced using neural networks. To unambiguously distinguish yet unknown CP-even from possible CP-odd effects, a variable whose shape asymmetry only depends on CP-odd effects is built. This observable is based on the matrix element computation, maximally using the kinematic information available from Higgs boson and associated jets. Results are interpreted in a context of effective field theory, and the statistical precision on the tCzz Wilson coefficient is estimated to [-0.80, 0.80] at the 68% confidence level.Après la découverte du boson de Higgs en 2012 au LHC, l'intérêt s'est porté sur l'étude de ses propriétés pour vérifier le Modèle Standard et pour sonder la nouvelle physique. L'une de ses propriétés fondamentales est sa spin-parité (CP), dont le Modèle Standard prédit la valeur 0+. Les analyses menées sur les données récoltées au Run 1 du LHC ont rejeté toutes les hypothèses d'état pur de spin-parité autre que cette valeur. Cependant des états mixtes de CP sont toujours possibles, ce qui indiquerait une violation de symmétrie CP dans le secteur du Higgs.La première partie de cette thèse se concentre sur la calibration du calorimètre électromagnétique d'ATLAS permettant d'atteindre une résolution de l'ordre du pour mille sur l'énergie des électrons et photons, primordiaux dans les analyses du boson de Higgs. Une des étapes est l'inter-calibration des couches du calorimètre électromagnétique, corrigeant des effets résiduels de calibration électronique et de diaphonie (cross-talk). La méthode établie au Run 1 a montré ses limites devant les niveaux d'empilement mesurés au Run 2, et une nouvelle analyse a été alors dévéloppée, assurant le contrôle précis des incertitudes systématiques.La deuxième partie de cette thèse porte sur la mesure des couplages CP-impairs du boson de Higgs aux boson vecteurs, étudié dans le canal de désintégration du boson de Higgs en quatre leptons. Malgré une faible statistique, ce canal offre une signature propre et un rapport signal sur bruit de plus de deux, permettant l'analyse précise des propriétés du boson de Higgs. Le mode de production par fusion de bosons vecteurs offre la meilleure sensibilité aux effets de CP grâce à la présence de deux jets dans l'état final. La pollution venant du mode de production par fusion de gluon avec des jets additionels est réduite grâce à l'utilisation de réseaux neuronaux. Pour distinguer de manière univoque les effets CP-impair d'éventuels effets CP-pair encore inconnus, une nouvelle variable est construite dont l'asymétrie de forme dépend uniquement d'effets CP-impairs. Composée d'éléments de matrice, cette variable utilise les informations cinématiques du boson de Higgs et des jets de manière maximale. Les résultats sont interprétés en termes de théorie effective, et la sensibilité statistique à 68% de confiance sur le coefficient de Wilson tCzz est estimée à [-0.80, 0.80]

    Measurement of differential cross sections and of the Higgs boson mass in Higgs boson decays to bosons using the ATLAS detector

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    Despite small branching fractions, the H→γγH \to \gamma\gamma and H→ZZ∗→4ℓH \to ZZ^* \to 4\ell Higgs boson decays provide clean and well reconstructed final states, allowing for precise measurements of the Higgs boson properties. These proceedings present measurements of total and differential fiducial cross sections in the H→γγH \to \gamma\gamma and H→ZZ∗→4ℓH \to ZZ^* \to 4\ell decay channels, and a mass measurement in the H→ZZ∗→4ℓH \to ZZ^* \to 4\ell decay channel. The total fiducial cross section is measured to be σfidγγ=65.2±7.1\sigma^{\gamma\gamma}_{\text{fid}} = 65.2 \pm 7.1 fb in the H→γγH \to \gamma\gamma channel and σfid4ℓ=3.28±0.32\sigma^{4\ell}_{\text{fid}} = 3.28 \pm 0.32 fb in the H→ZZ∗→4ℓH \to ZZ^* \to 4\ell channel, in agreement with the Standard Model predictions. Differential cross-section measurements are reported for Higgs boson production- and decay-related observables. The Higgs boson transverse momentum differential cross-section distributions are used to constrain the charm Yukawa coupling modifier (95% confidence level interval on κc\kappa_c of [−12,11][-12, 11] in the H→4ℓH \to 4\ell analysis and of [−19,24][-19, 24] in the H→γγH \to \gamma\gamma analysis). Other differential distributions allow constraints on pseudo-observables and effective field theory coefficients. The Higgs boson mass in the H→ZZ∗→4ℓH \to ZZ^* \to 4\ell decay channel is measured to be mH=124.92±0.19 (stat.)−0.06+0.09 (sys.) m_H = 124.92 \pm 0.19 \, \text{(stat.)}^{+0.09}_{-0.06} \, \text{(sys.) } GeV. All the results are derived using 139 fb−1^{-1} of s=13\sqrt{s} = 13 TeV proton-proton collisions collected with the ATLAS detector during the Run 2 of the LHC

    Layer Intercalibration of the ATLAS Electromagnetic Calorimeter and CP-odd Higgs Boson Couplings Measurements in the Four-Lepton Decay Channel with Run 2 Data of the LHC

    No full text
    After the Higgs boson discovery at the LHC in 2012, interest turned to Higgs boson property measurements to refine the tests of the Standard Model and probe for new physics. One of its key properties is its spin-parity (CP), predicted to be 0+0^+ in the Standard Model. Analyses of data collected during the Run 1 of the LHC rejected all pure spin-parity state other than 0+0^+. However mixed CP states are still possible, and would indicate CP violation in the Higgs sector. The first part of this thesis focuses on the ATLAS electromagnetic calorimeter calibration, needed to reach a permil level on electron and photon energy resolution which are of prime importance for Higgs boson studies. One step of the calibration sequence consists of the layer intercalibration of the electromagnetic calorimeter, needed to correct residual electronics miscalibration and cross-talk effects. The Run 1 method has proven to be unreliable for the pileup levels in Run 2 and a new method was developed, ensuring a precise control on the systematic uncertainties. The second part of this thesis puts emphasis on the Higgs boson to vector boson CP-odd couplings, with the Higgs boson decaying to four leptons. This channel, despite low statistics, provides a clean signature and a signal-to-noise ratio over two, allowing for a precise determination of the Higgs boson properties. The vector boson fusion production channel offers the best sensitivity to CP effects thanks to its two characteristic tagging jets in the final state. The contamination from the gluon fusion production mode with additional jets is reduced using neural networks. To unambiguously distinguish yet unknown CP-even from possible CP-odd effects, a variable whose shape asymmetry only depends on CP-odd effects is built. This observable is based on the matrix element computation, maximally using the kinematic information available from Higgs boson and associated jets. Results are interpreted in a context of effective field theory, and the statistical precision on the c~zz\tilde{c}_{zz} Wilson coefficient is estimated to [−0.80,0.80][-0.80, 0.80] at the 68% confidence level

    The DUNE Far Detector Vertical Drift Technology, Technical Design Report

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    International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

    The DUNE Far Detector Vertical Drift Technology, Technical Design Report

    No full text
    International audienceDUNE is an international experiment dedicated to addressing some of the questions at the forefront of particle physics and astrophysics, including the mystifying preponderance of matter over antimatter in the early universe. The dual-site experiment will employ an intense neutrino beam focused on a near and a far detector as it aims to determine the neutrino mass hierarchy and to make high-precision measurements of the PMNS matrix parameters, including the CP-violating phase. It will also stand ready to observe supernova neutrino bursts, and seeks to observe nucleon decay as a signature of a grand unified theory underlying the standard model. The DUNE far detector implements liquid argon time-projection chamber (LArTPC) technology, and combines the many tens-of-kiloton fiducial mass necessary for rare event searches with the sub-centimeter spatial resolution required to image those events with high precision. The addition of a photon detection system enhances physics capabilities for all DUNE physics drivers and opens prospects for further physics explorations. Given its size, the far detector will be implemented as a set of modules, with LArTPC designs that differ from one another as newer technologies arise. In the vertical drift LArTPC design, a horizontal cathode bisects the detector, creating two stacked drift volumes in which ionization charges drift towards anodes at either the top or bottom. The anodes are composed of perforated PCB layers with conductive strips, enabling reconstruction in 3D. Light-trap-style photon detection modules are placed both on the cryostat's side walls and on the central cathode where they are optically powered. This Technical Design Report describes in detail the technical implementations of each subsystem of this LArTPC that, together with the other far detector modules and the near detector, will enable DUNE to achieve its physics goals

    The DUNE Far Detector Vertical Drift Technology, Technical Design Report