Jet Structure Studies in Small Systems

Zoltán Varga,Róbert Vértesi,Gergely Gábor Barnaföldi

doi:10.3390/universe5050132

Zoltán Varga, Róbert Vértesi + Show 1 more

Open Access

https://doi.org/10.3390/universe5050132

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Abstract

A study investigating a possible jet shape dependence on the charged event multiplicity was performed on collision samples generated by Monte–Carlo (MC) event generators Pythia and Hijing++. We calculated the integral jet shape and found a significant modification caused by multiple-parton interactions. By interchanging and enabling different model ingredients in the simulations and analyzing the results in several     p T    bins and event multiplicity classes, we found a characteristic jet size measure that was independent of the chosen tunes, settings, and jet reconstruction algorithms.

Highlights

The discovery of collective-like behavior in high-multiplicity proton-proton and proton-nucleus collisions was one of the major surprises in early LHC results [1,2].The collective-like behavior previously found in large systems, manifested in long-range correlations and a sizeable azimuthal anisotropy, have traditionally been considered as a signature proving the presence of the quark-gluon plasma (QGP)
A significant change is observed when we do not consider the effects of the color reconnection and/or the multiple-parton interactions
We conducted a systematic study on jet structures for pp collisions using MC generators P YTHIA

Summary

Introduction

The discovery of collective-like behavior in high-multiplicity proton-proton (pp) and proton-nucleus (pA) collisions was one of the major surprises in early LHC results [1,2]. The creation of the QGP in high-energy nucleus-nucleus (AA) collisions can be investigated by studying the structure of jets and their modification that leads to the well-known jet quenching phenomenon [3,4]. The presence of the QGP is not necessary to explaining collectivity: Relatively soft vacuum-QCD effects such as multiple-parton interactions (MPI). Color reconnection (CR) can produce a similar behavior [6,7] These interactions, at least in principle, can modify the jet shapes in even small systems. Experimental confirmation is not yet available, a recent phenomenology study suggests the modification of hard processes by soft vacuum-QCD effects in a high-multiplicity environment [8]. Fragmentation of heavy-flavor jets is expected to differ from light-flavor jets because of color charge and mass effects.

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