Pile-up Background Estimation in Diboson Production by the Overlay Monte Carlo Method in pp Collider Experiment

In case of diboson production in $$pp$$ collisions there is a non-negligible probability that some events passing the final selection in data are actually from different overlapping hard-scatter processes occurring within the same bunch-crossing. Such events, that consist of combination of two processes associated with different primary vertices, correspond to so-called pile-up background. Its contribution should be considered in analysis of diboson production at collider experiments. This article discusses an overlay Monte Carlo approach to obtain a theoretical prediction of the pile-up event count. According to the resulting estimate of the proposed method the impact of the pile-up background can be either subtracted from the data in the region of interest or accounted as an additional systematic uncertainty for the final result.