Speaker
Description
Top quark pair-production in association with one or two additional $b$-jets is one of the main backgrounds in the search for $t\bar{t}+H$ production, and in BSM physics searches involving top and bottom quarks in the final states. Precise measurement of $t\bar{t}+b$ and $t\bar{t}+bb$ differential cross sections will help to significantly reduce systematic and modeling uncertainties in future BSM searches and measurements of the top-Higgs coupling. A BDT that discriminates between $b$-jets which do or do not originate from top quarks decays has been developed in the opposite-sign dilepton channel. The method has higher purity compared to the existing method based on the angular distributions between $b$-jets and leptons. Preliminary results show that with the new method we can accurately measure the $p_{T}$ spectra of $b$-jets from top quark decays and of the leading additional $b$-jet up to 400 GeV, and the sub-leading additional $b$-jets $p_{T}$ up to 300 GeV. The analysis uses LHC proton-proton collision data at the center-of-mass energy $\sqrt{s}=13$ TeV with an integrated luminosity of 139 fb$^{-1}$ collected with the ATLAS detector in 2015-2018.
| Career stage | Graduate student |
|---|
