  The underlying event is an important part of high-energy collision events. In
the event generators, the underlying event is tuned by fits to collision data.
Usually, the underlying event observables are affected by the existence of
extra jets and it is difficult to find a part of the phase space which is
dominated by the underlying event. In this paper, we suggest to veto the jets
in the considered region to disentangle these effects. The idea is verified to
work on CMS Open Data. To our knowledge, it is the first time that such ideas
are tested on real collision data.
