Event shapes and jets in $e^{+}e^{-}$ and pp collisions

TL;DR

This paper examines how event shape observables like transverse sphericity relate to jet multiplicity in high energy collisions, revealing differences between $e^{+}e^{-}$ and pp collisions using PYTHIA simulations.

Contribution

It demonstrates that transverse sphericity effectively discriminates jet topologies in $e^{+}e^{-}$ collisions but not in pp collisions, highlighting the influence of multi-parton interactions.

Findings

Transverse sphericity correlates with jet number in $e^{+}e^{-}$ collisions.

In pp collisions, transverse sphericity is sensitive to multi-parton interactions.

The study challenges previous assumptions about event shape observables in pp collisions.

Abstract

In high energy particle collisions the shape of the event, i.e. the relative distribution of particles in momentum space, is often used to try to select events with certain topologies. It is claimed that an event shape observable like transverse sphericity is able to discriminate between jet-like events and events that are dominated by soft production from the underlying event. In this paper we investigate the relationship between the shape of the event and the number of jets found in the respective event for both $e^{+}e^{-}$ and pp collisions using the PYTHIA model. In $e^{+}e^{-}$ collisions, we find that the transverse sphericity of the event can be used effectively to either enhance or suppress the fraction of jets found in the selected sample, and can even discriminate between single, two, and multi-jet topologies. However, contrary to current literature, we find that in pp collisions this does not hold. It is shown that the transverse sphericity as well as the particle multiplicity is sensitive to the number of multi-parton interactions.