Hard radiation in top quark decays

Due to concerns regarding the gluon emission recoil in top quark modelling, it's been suggested to treat the top quark as recoiler in $t \rightarrow bW$ decay. To test this as a possibility to reduce the top mass measurement uncertainty, an analysis is done on the $t\Bar{t}$ semileptonic decay channel by looking for hard radiation outside \textit{b}-jet cones and reconstructing it as either an additional soft jet (for hadronic decay) or as a fat \textit{b}-jet (for leptonic decay) with the goal to find differences between RTT and mass or FSR variations. The soft jet study shows no significant differences for RTT, but succeeded in enriching the sample in FSR events. The fat jet substructure study shows promise for the subjet $\Delta$R observable, showing distinct shape for the RTT sample. A fast simulation of CMS detector effects was applied, demonstrating that this should also be measurable in CMS data.