Dortmund 2021 – scientific programme
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T: Fachverband Teilchenphysik
T 4: Quark mixing and CP violation
T 4.6: Talk
Monday, March 15, 2021, 17:15–17:30, Td
Event reconstruction techniques in the context of a Higgs boson CP analysis in the di-tau lepton final state with the CMS experiment — Olena Hlushchenko, Sven Krausse, Wolfgang Lohmann, Dennis Roy, Hale Sert, Sebastian Siebert, Achim Stahl, and •Alexander Zotz — RWTH Aachen University - Physics Institute III B, Aachen, Germany
In 2020 the first measurement of the effective CP mixing angle in Higgs boson decay into two tau leptons has been performed by the CMS experiment. It was determined to be (4±17)∘ using the Run 2 data set of pp collisions of 137 fb−1 integrated luminosity. The mixing angle was extracted from a distribution of angles between the decay planes of the tau lepton decay products in the H→ττ decay. In the case of hadronic tau lepton decays via the intermediate a1 resonance the full tau lepton kinematics including its neutrino and furthermore its polarimetric vector can be reconstructed. Requiring both tau leptons to decay via a1 mesons allows for the reconstruction of a CP sensitive observable with higher sensitivity. However the a1a1 final state suffers from a small branching fraction and therefore these improvements have a neglible effect on the overall sensitivity once all final states are included. In this talk, an extension of the polarimetric vector method via the inclusion of final states with an a1 decay on one side and a single charged lepton or hadron on the other side of the H→ττ decay is presented. To reconstruct the event a kinematic fit with external constraints is used and the potential improvement on the measurement of the CP mixing angle is discussed.