Seminário CAT

Study of the Spin/CP properties of the Higgs coupling to W-bosons with ATLAS at the LHC

Ricardo Barrué

Quarta-feira, 26 de Outubro de 2022 das 09:30 às 11:30
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Online (Meeting ID: 657 2811 7852 Passcode: 716650)

Abstract:

Sources of CP violation beyond the Standard Model (SM) are necessary to account for the observed matter-antimatter asymmetry in the Universe. Despite the significant progress in the experimental exploration of the Higgs sector in the last ten years and the overall agreement of the current results with the expectations of the SM, the experimental precision is not yet sufficient to constrain anomalous Higgs boson interactions. The work presented here focuses on the search for CP violation in the HWW interaction vertex in events where a Higgs boson is produced in association with a W boson, when the Higgs decays to a pair of b-quark jets and the W boson to a charged lepton and a neutrino. 


Several groups have proposed different observables to search for anomalous couplings in the HWW vertex. In order to optimise the experimental sensitivity to such couplings, the most promising angular observables proposed in the literature were compared to novel machine-learning inference methods that allow building (statistically) optimal observables without approximating the detector response. The results show that a combination of energy-related and angular observables is competitive with the current version of the tested machine-learning inference techniques.


All these methods require the best possible experimental resolution in the measurement of the final state particles. The identification of b-jets, as well as the measurement of their energy and momentum, is very challenging experimentally and requires dedicated calibration samples, as well as analysis techniques. Collecting large, unbiased samples of jets for calibration requires an efficient and optimised jet trigger system. The ATLAS jet trigger was upgraded for Run 3, introducing full-event scan tracking and calorimeter+track jet reconstruction. This presentation will also cover several studies done to study and optimise the jet's trigger efficiency and CPU costs.