The hard physics of soft muons: novel measurement of the top-quark mass and differential cross-sections of top-quark pair production using the ATLAS detector at the LHC

The mass of the top quark is measured in lepton+jets top-quark pair events with an experimental technique exploits the semileptonic decay of $b$ hadrons. An invariant mass is constructed between the lepton from the $W$-boson decay and a soft muon originating from a $b$-hadron decay. A binned-template likelihood fit is performed to the invariant mass distribution yielding the most precise \ATLAS measured value of the top-quark mass of $m_t = 174.44 \pm 0.76\,\textrm{(stat+syst)}\, \textrm{GeV}$. Measurements of differential cross-sections of top-quark pair production are performed as a function of several observables related to the decay of the $W$ boson and $b$ hadron. These measured cross-sections are compared to various predictions.