Jets and Centrality in p(d)-A Collisions

TL;DR

This paper investigates jet production and centrality effects in p(d)-A collisions at RHIC and LHC, revealing that observed modifications are mainly due to event mis-binning caused by energy depletion after jet production.

Contribution

It introduces a hybrid Monte-Carlo model that explains centrality-dependent jet modifications as a result of parton energy depletion and mis-binning effects in p(d)-A collisions.

Findings

Peripheral events show jet enhancement due to mis-binning.

Central events exhibit jet depletion linked to energy depletion.

The model suggests a form of color transparency affecting jet production.

Abstract

The production of jets, and high-$p_{T}$ leading pions from jets, in d-Au collisions at the Relativistic Heavy-Ion Collider (RHIC) and p-Pb collisions at the Large Hadron Collider (LHC) are studied. Using a modified version of the event generator PYTHIA, in conjunction with a nuclear Glauber Monte-Carlo event generator, we demonstrate how events with a hard jet may be simulated, in such a way that the parton distribution function of the projectile nucleon is frozen during its interaction with the extended nucleus. Using our hybrid Monte-Carlo event generator, we demonstrate that the enhancement in $R_{pA}$ seen in peripheral events at RHIC and at LHC, as well as the depletion in central or semi-central events, is mainly due to "mis-binning" of central and semi-central events with a jet, as peripheral events. This occurs due to the reduction of soft particle production caused by a depletion of energy available in a nucleon (of the deuteron in the case of d-Au collisions), after the production of a hard jet. This represents a form of "color transparency" of the projectile nucleon, which has fluctuated to a state with fewer and harder partons, in events which lead to jet production. We conclude with discussions of the form of multi-parton correlations in a nucleon which may be responsible for such a startling effect.