Phenomenology of t t ¯ j $$ t\overline{t}j $$ + X production at the LHC

We present phenomenological results for $$ t\overline{t}j $$ + X production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the $$ t\overline{t}j $$ + X process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the $$ \mathcal{R} $$ distribution, which depends on the invariant mass of the $$ t\overline{t}j $$ -system, we present reference predictions in the on-shell, $$ \overline{\mathrm{MS}} $$ and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the top-quark mass from cross-section measurements.