Theory Seminar (High Energy/Cosmology)

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Disentangling the Top-Higgs Yukawa CP Structure in the Dileptonic tth with M2-?Assisted reconstructions
Date: Tuesday, April 10th
Time: 3:30 pm
Place: 5280 Chamberlin Hall
Speaker: Jeong Han Kim, University of Kansas
Abstract: The top quark plays a crucial role in the production and the decays of the Higgs boson, and its Yukawa coupling is constrained by various indirect precision measurements but only via loop-effects. Therefore it is imperative to make a direct measurement of the Top quark Yukawa coupling. In particular, an additional source of CP violation in new physics beyond the standard model may induce the pseudo-scalar component in the Top-Higgs interaction and there are many proposals to measure the relative contribution of CP-even and CP-odd interactions. Since the CP admixture property may be best measured in the center-of-mass frame of either tth or tt system, the majority of currently available methods examine the CP nature in either hadronic or semi-leptonic final states. Existing studies in the dilepton final state are performed in the laboratory frame, which provides limited information on this interaction. In this paper, we investigate the Top-Higgs Yukawa interaction in the dilepton final state and attempt full kinematic reconstructions of both top quarks, which allows to Lorentz-boost to any frame of our interest. We first study event reconstructions at parton level and show that the kinematic correlations survive even after inclusion of more realistic effects such as a parton-shower and hadronization. As a result, we present the required luminosity at the HL-LHC, to distinguish the SM Higgs from an arbitrary CP state, based on a binned log-likelihood method.
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