Abstract
The integrated fiducial cross-section and unfolded differential jet mass spectrum of high transverse momentum Z→bb̅ decays are measured in Zγ events in proton–proton collisions at √s = 13TeV. The data analysed were collected between 2015 and 2016 with the ATLAS detector at the Large Hadron Collider and correspond to an integrated luminosity of 36.1 fb-1. Photons are required to have a transverse momentum pT >175 GeV. The Z→bb̅ decay is reconstructed using a jet with pT >200 GeV, found with the anti-kt R=1.0 jet algorithm, and groomed to remove soft and wide-angle radiation and to mitigate contributions from the underlying event and additional proton–proton collisions. Two different but related measurements are performed using two jet grooming definitions for reconstructing the Z→bb̅ decay: trimming and soft drop. These algorithms differ in their experimental and phenomenological implications regarding jet mass reconstruction and theoretical precision. To identify Z bosons, b-tagged R=0.2 track-jets matched to the groomed large-R calorimeter jet are used as a proxy for the b-quarks. The signal yield is determined from fits of the data-driven background templates to the different jet mass distributions for the two grooming methods. Integrated fiducial cross-sections and unfolded jet mass spectra for each grooming method are compared with leading-order theoretical predictions. The results are found to be in good agreement with Standard Model expectations within the current statistical and systematic uncertainties.
Original language | English |
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Article number | 135991 |
Number of pages | 23 |
Journal | Physics Letters B |
Volume | 812 |
Early online date | 3 Dec 2020 |
DOIs | |
Publication status | Published - 10 Jan 2021 |
Bibliographical note
37 pages in total, author list starting page 21, 3 figures, 5 tables, submitted to Phys. Lett. B. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-14/ASJC Scopus subject areas
- Nuclear and High Energy Physics