Jets in d(p)-A Collisions: Color Transparency or Energy Conservation

TL;DR

This paper investigates jet production in d-Au and p-Pb collisions, showing that observed centrality-dependent effects are mainly due to event mis-binning caused by energy conservation effects, rather than new physics.

Contribution

It introduces a modified PYTHIA-based simulation approach that accounts for energy conservation, explaining centrality effects without invoking additional phenomena.

Findings

Peripheral enhancement and central suppression are due to event mis-binning.

Energy depletion in nucleons explains soft particle suppression.

Partonic correlations from energy conservation account for the observed effects.

Abstract

The production of jets, and high momentum hadrons from jets, produced in deuteron ($d$)-$Au$ collisions at the relativistic heavy-ion collider (RHIC) and proton ($p$)-$Pb$ collisions at the large hadron collider (LHC) are studied as a function of centrality, a measure of the impact parameter of the collision. A modified version of the event generator PYTHIA, widely used to simulate $p$-$p$ collisions, is used in conjunction with a nuclear Monte-Carlo event generator which simulates the locations of the nucleons within a large nucleus. We demonstrate how events with a hard jet may be simulated, in such a way that the parton distribution function of the projectile is frozen during its interaction with the extended nucleus. Using our approach, we demonstrate that the puzzling enhancement seen in peripheral events at RHIC and the LHC, as well as the suppression seen in central events at the LHC are mainly due to mis-binning of central and semi-central events, containing a jet, as peripheral events. This occurs due to the suppression of soft particle production away from the jet, caused by the depletion of energy available in a nucleon of the deuteron (in $d$-$Au$ at RHIC) or in the proton (in $p$-$Pb$ at LHC), after the production of a hard jet. We conclude that partonic correlations built out of simple energy conservation are mostly responsible for such an effect.