Shower it again, Pythia

The Parton-Shower algorithm implement in the Pythia generator is applied multiple times to the same parton-level configuration to estimate the systematic uncertainty affecting large-radius jet substructure variables associated with the stochastic nature of the algorithm. Results are presented in the case of boosted $h\to b\bar{b}$ and $t\to bqq$. The code is publicly available on the repository https://github.com/rdisipio/ReShower.git