Search for Higgs boson pair production in the bbtautau final state with the ATLAS detector and machine learning for pion identification in hadronic tau decays
by
Christina Dimitriadi(Uppsala University)
→
Europe/Stockholm
Beurlingrummet
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Description
After the discovery of the Higgs boson in 2012, an important test of the electroweak symmetry breaking would be to establish evidence of the Higgs boson self-coupling (lambda_{HHH}), which can be achieved through a measurement of Higgs boson pair production. In the Standard Model (SM), di-Higgs events are dominantly produced in gluon-gluon fusion processes at the LHC, e.g. involving the Yukawa coupling to top quarks (top-quark loops) or via the Higgs boson self-coupling. These two production modes interfere destructively, which leads to a very small di-Higgs production cross-section. However, deviations in couplings of the Higgs boson from SM expectation could lead to a significant enhancement of the di-Higgs production rate. A re-interpretation of the search for non-resonant Higgs boson pair production in the bbtautau channel, which is one of the most sensitive for probing the Higgs self-coupling, is presented. A scan of the coupling modifier, kLambda = lambda_{HHH}/lambda_{HHH}(SM), is performed and exclusion limits on kLambda are set. Projected sensitivity results at the High-Luminosity LHC are also discussed and preliminary results of Higgs Effective Field Theory interpretations of the existing analysis are shown. Finally, an overview of my service task within the Tau Performance group is given, which involves the exploration of machine learning techniques for tau identification and energy calibration with ATLAS.