A look into the “hedgehog” events in pp collisions
The UA1 and CDF collaborations have reported the presence of events with a very extended structure of low momentum tracks filling in a uniform way the η − ϕ phase space. However, these events have not caused interest with respect to the details of the interaction that provoke them. We have undertaken to study whether such events are predicted by present event generators like PYTHIA 8. We report the existence of events without any discernible jetty structure in high-multiplicity pp collisions. In the simulations those events originate from several parton-parton scatterings within the same pp collision. We introduce the event shape ρ (f latenicity) as a tool to tag those events in experiments.
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