Measurement of the top-quark mass using decays with a $J/\psi$ meson at $\sqrt{s}=$13 TeV with the ATLAS detector

Abstract

The top-quark mass is measured using top-quark decays producing an isolated lepton and $J/\psi$ meson reconstructed in its ${\mu }^{+}{\mu }^{-}$ decay mode. The data sample was recorded with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb${}^{-1}$. The measurement is based on the invariant mass $m(\ell {\mu }^{+}{\mu }^{-})$ of the system made of the isolated lepton $\ell$ from the $W$ boson decay and the non-isolated ${\mu }^{+}{\mu }^{-}$ pair from a $J/\psi$ decay of a $b$-hadron, exploiting its sensitivity to the top-quark mass. An unbinned maximum-likelihood fit to the $m(\ell {\mu }^{+}{\mu }^{-})$ distribution is performed to extract the top-quark mass. The top-quark mass is measured to be $m_{top}=172.17\pm 0.80(stat)\pm 0.81(syst)\pm 1.07(recoil)$ GeV, with a total uncertainty of 1.56 GeV. The third uncertainty arises from changing the dipole parton shower gluon-recoil scheme used in top-quark decays.

50 pages in total, author list starting page 33, 19 figures, 8 tables, published on JHEP. All figures including auxiliary figures are available at <http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2018-19>. HEP-Data record at <https://www.hepdata.net/record/ins3087833>