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Measurement of the c-jet mistagging efficiency in $$t\bar{t}$$ events using pp collision data at $$\sqrt{s}=13$$ $$\text {TeV}$$ collected with the ATLAS detector

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  • ATLAS Collaboration
Article number95
<mark>Journal publication date</mark>31/01/2022
<mark>Journal</mark>European Physical Journal C
Issue number1
Number of pages27
Publication StatusPublished
<mark>Original language</mark>English


A technique is presented to measure the efficiency with which c-jets are mistagged as b-jets (mistagging efficiency) using $$t\bar{t}$$ t t ¯ events, where one of the W bosons decays into an electron or muon and a neutrino and the other decays into a quark–antiquark pair. The measurement utilises the relatively large and known $$W\rightarrow cs$$ W → c s branching ratio, which allows a measurement to be made in an inclusive c-jet sample. The data sample used was collected by the ATLAS detector at $$\sqrt{s} = 13$$ s = 13 $$\text {TeV}$$ TeV and corresponds to an integrated luminosity of 139 fb$$^{-1}$$ - 1 . Events are reconstructed using a kinematic likelihood technique which selects the mapping between jets and $$t\bar{t}$$ t t ¯ decay products that yields the highest likelihood value. The distribution of the b-tagging discriminant for jets from the hadronic W decays in data is compared with that in simulation to extract the mistagging efficiency as a function of jet transverse momentum. The total uncertainties are in the range 3–17%. The measurements generally agree with those in simulation but there are some differences in the region corresponding to the most stringent b-jet tagging requirement.