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Public Seminar of RPg Student:
Search for New Phenomena in tt ̅ Final States with Heavy Higgs Bosons in pp Collisions at √s = 13 TeV with the ATLAS Detector


Speaker:Mr. Kai Chung TAM
Affiliation:The University of Hong Kong
Date:March 21, 2019 (Thursday)
Time:3:00 p.m.
Venue:Rm 518, 5/F, Chong Yuet Ming Physics Building, HKU

Abstract
 

After the Higgs bosons confirm the final piece of evidence in the Standard Model (SM), the deviations from BSM (BSM) have been searched. One of the BSM is that the number of doublets of the Higgs sector is assumed to be two (2HDM).

A search for new top-quark pair (tt ̅) final states associated with a scalar (H) or pseudoscalar (A) heavy Higgs boson decaying into another top-quark pair (tt ̅H/A→tt ̅tt ̅) is presented. All the top-quarks decays into a W boson and a bottom-quark both leptonically and hadronically according to their branching ratio Br(t→Wb). The data is collected at the integrated luminosity of 150 fb-1 by the ATLAS detector at the CERN Large Hadron Collider in proton-proton collision at a center-of-mass energy √s=13 TeV. To separate the signal and background, the discriminating variables are chosen by the boost decision tree method and neural network method. The background model is fitted to the data by likelihood fit method in order to have a clear understanding about the background. For having no significant deviations from SM, 95% CL upper limits for parameters β ,cos⁡(α-β) and MH in 2HDM in the statistical analysis.

Anyone interested is welcome to attend.