Study of the underlying event, b-quark fragmentation and hadronization properties in tbart events

Exploratory studies of the underlying event (UE) activity and of the fragmentation and hadronization of ${\rm b}$ quarks in final states containing a ${\rm J}/\psi$ are performed using ${\rm t\bar{t}}$ candidate events. Proton-proton collision data acquired by the CMS experiment at a centre-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 19.7~fb$^{-1}$ are used. A good agreement is found using \textsc{MadGraph} plus the \textsc{Pythia} 6 Tune Z2$^*$ simulation. The effects predicted by alternative settings and generators for the characterization of the UE are also explored. These results are expected to contribute in the future to more precise measurements in the top quark sector in particular of the top quark mass by either constraining systematic uncertainties related to the modelling of the UE in ${\rm t\bar{t}}$ events or by paving the way for alternative mass measurement methods.