Measurements of Higgs boson production cross sections in the H -> tau tau decay channel in pp collisions at sqrt(s) = 13 TeV with the ATLAS detector

The coupling of the Higgs boson to tau leptons is one of the most precise measured couplings of the Higgs boson to fermions. A measurement of the production cross sections of the Higgs boson into two tau leptons is presented. The cross section is measured in the gluon-fusion, vector-boson-fusion, boson associated, and top-quark pair associated production channels. The result is shown in the context of Simplified Template Cross Sections. The study illustrates the technique for the Higgs boson mass reconstruction (Missing Mass Calculator, MMC). The analysis uses proton-proton collision data recorded during Run 2 at a center-of-mass energy sqrt(s) = 13 TeV with the ATLAS detector at the LHC

Studies of Higgs boson in its decay to a pair of tau-leptons and search for excited tau-lepton with the ATLAS detector

The Standard Model (SM) describes known elementary particles and their interactions. The ATLAS experiment is located at the Large Hadron Collider (LHC) in CERN (Geneva). The ATLAS detector measures data from proton- proton collisions at high centre-of-mass energy. The collected data allow physi- cists to precisely study SM and look for evidence of particles beyond the Stan- dard Model. The presented thesis describes the analysis of Higgs boson decay to a pair of tau-leptons. The measurement of the Higgs boson production cross section is based on the data set collected by the ATLAS detector in proton-proton (pp) collisions at a centre-of-mass energy of 13 TeV in the years 2015-18 (so-called Run 2). This dissertation presents the update of the algorithm of Higgs boson mass reconstruction for the Run 2 ATLAS conditions. The evaluation of fake tau-lepton background is also discussed. Further, this dissertation is dedicated to the search for excited tau-leptons in the Run 2 ATLAS data set. Contact interaction of the excited tau-leptons is assumed, which would occur if fermions were composite rather than elemen- tary. The analysed ATLAS data from pp collisions in Run 2 set do not contain signatures of excited tau-leptons production. Within the considered model with the compositeness scale Λ = 10 TeV, the upper..

Studium Higgsova bosonu v jeho rozpadu na pár tau leptonů a hledání excitovaných tau leptonů v experimentu ATLAS

Standardní model popisuje známé elementární částice a interakce mezi nimi. Experiment ATLAS se nachází na velkém hadronovém urychlovači (LHC) v CERNu (Ženeva). Detektor ATLAS měří data ze srážek protonů o vysoké těžiš- t'ové energii. Shromažd'ovaná data umožňujífyzikům studovat standardnímodel s velkou přesností. Navíc, naměřená data ze srážek by mohly obsahovat důkazy o existenci částic mimo standardní model. Prezentována práce popisuje analýzu rozpadu Higgsova bosonu na pár tau leptonů. Měření účinného průřezu produkce Higgsova bosonu je provedeno v datech z detektoru ATLAS, naměřených v proton-protonových (pp) srážkách o těžišt'ové energií 14 TeV v letech 2015-18 (tzv. Run 2). V disertaci je popsána aktualizace algoritmu rekonstrukce hmoty Higgsova bosonu. Uvedena je také problematika odhadu falešného (tzv. fake) tau-leptonového pozadí. Dále se tato disertační práce věnuje hledání excitovaných tau leptonů. Před- pokládá se kontaktní interakce excitovaných tau leptonů, což by bylo možné, kdyby fermiony byly spíše složené než elementární. Hledáníexcitovaných tau lep- tonů bylo provedeno v souboru dat sebraných detektorem ATLAS v pp srážkách během Run 2. Avšak, v těchto datech nebyly nalezeny...The Standard Model (SM) describes known elementary particles and their interactions. The ATLAS experiment is located at the Large Hadron Collider (LHC) in CERN (Geneva). The ATLAS detector measures data from proton- proton collisions at high centre-of-mass energy. The collected data allow physi- cists to precisely study SM and look for evidence of particles beyond the Stan- dard Model. The presented thesis describes the analysis of Higgs boson decay to a pair of tau-leptons. The measurement of the Higgs boson production cross section is based on the data set collected by the ATLAS detector in proton-proton (pp) collisions at a centre-of-mass energy of 13 TeV in the years 2015-18 (so-called Run 2). This dissertation presents the update of the algorithm of Higgs boson mass reconstruction for the Run 2 ATLAS conditions. The evaluation of fake tau-lepton background is also discussed. Further, this dissertation is dedicated to the search for excited tau-leptons in the Run 2 ATLAS data set. Contact interaction of the excited tau-leptons is assumed, which would occur if fermions were composite rather than elemen- tary. The analysed ATLAS data from pp collisions in Run 2 set do not contain signatures of excited tau-leptons production. Within the considered model with the compositeness scale Λ = 10 TeV, the upper...Ústav částicové a jaderné fyzikyInstitute of Particle and Nuclear PhysicsMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Time calibration, monitoring and performance of the ATLAS Tile Calorimeter in Run 2

The Tile Calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the LHC. It is made of steel plates acting as absorber and scintillating tiles as active medium. The TileCal response is calibrated to electromagnetic scale by means of several dedicated calibration systems. The accurate time calibration is important for the energy reconstruction, non-collision background removal as well as for specific physics analyses. The initial time calibration using so-called splash events and subsequent fine-tuning with collision data are presented. The monitoring of the time calibration with laser system and physics collision data is discussed as well as the corrections for sudden changes performed still before the recorded data are processed for physics analyses. Finally, the cell time resolution as measured with jet events in Run 2 is presented

Time calibration, monitoring and performance of the ATLAS Tile Calorimeter in Run 2

The Tile Calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the LHC. It is made of steel plates acting as absorber and scintillating tiles as active medium. The TileCal response is calibrated to electromagnetic scale by means of several dedicated calibration systems. The accurate time calibration is important for the energy reconstruction, non-collision background removal as well as for specific physics analyses. The initial time calibration using so-called splash events and subsequent fine-tuning with collision data are presented. The monitoring of the time calibration with laser system and physics collision data is discussed as well as the corrections for sudden changes performed still before the recorded data are processed for physics analyses. Finally, the cell time resolution as measured with jet events in Run 2 is presented

Observation of WWWWWW Production in pppp Collisions at s\sqrt s =13 TeV with the ATLAS Detector

International audienceThis Letter reports the observation of $WWW$ production and a measurement of its cross section using 139 fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from $WWW$ production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive $WWW$ production cross section is measured to be $820 \pm 100\,\text{(stat)} \pm 80\,\text{(syst)}$ fb, approximately 2.6 standard deviations from the predicted cross section of $511 \pm 18$ fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy

Observation of WWWWWW Production in pppp Collisions at s\sqrt s =13 TeV with the ATLAS Detector

International audienceThis Letter reports the observation of $WWW$ production and a measurement of its cross section using 139 fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from $WWW$ production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive $WWW$ production cross section is measured to be $820 \pm 100\,\text{(stat)} \pm 80\,\text{(syst)}$ fb, approximately 2.6 standard deviations from the predicted cross section of $511 \pm 18$ fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy

Observation of WWWWWW Production in pppp Collisions at s\sqrt s =13 TeV with the ATLAS Detector

International audienceThis Letter reports the observation of $WWW$ production and a measurement of its cross section using 139 fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from $WWW$ production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive $WWW$ production cross section is measured to be $820 \pm 100\,\text{(stat)} \pm 80\,\text{(syst)}$ fb, approximately 2.6 standard deviations from the predicted cross section of $511 \pm 18$ fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy

Observation of WWWWWW Production in pppp Collisions at s\sqrt s =13 TeV with the ATLAS Detector

International audienceThis Letter reports the observation of $WWW$ production and a measurement of its cross section using 139 fb$^{-1}$ of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from $WWW$ production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive $WWW$ production cross section is measured to be $820 \pm 100\,\text{(stat)} \pm 80\,\text{(syst)}$ fb, approximately 2.6 standard deviations from the predicted cross section of $511 \pm 18$ fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy