Charged hadrons and nuclear parton distributions in p(d)A collisions

TL;DR

This paper investigates how various experimental observables in p(d)A collisions can be used to better constrain nuclear gluon modifications, which are currently poorly determined, especially at the LHC energies.

Contribution

It demonstrates the sensitivity of specific observables to nuclear gluon modifications and highlights the potential of LHC measurements to improve global fits.

Findings

Nuclear modification factor and pseudorapidity asymmetry are highly sensitive to gluon modifications.

Sensitivity to gluon modifications is significantly higher at LHC energies than at RHIC.

Charge ratio shows mild sensitivity, mainly at large Bjorken x.

Abstract

Nuclear gluon modifications are the least constrained component of current global fits to nuclear parton distributions, due to the inadequate constraining power of presently available experimental data from nuclear deep inelastic scattering and nuclear Drell-Yan lepton-pair production. A recent advance is the use of observables from relativistic nucleus-nucleus collisions to supplement the data pool for global fits. It is thus of interest to investigate the sensitivity of various experimental observables to different strengths of nuclear gluon modifications from large to small Bjorken $x$. In this work we utilize three recent global fits with different gluon strengths to investigate the sensitivity of three observables: nuclear modification factor, pseudorapidity asymmetry, and charge ratio. We observe that both nuclear modification factor and pseudorapidity asymmetry are quite sensitive to the strength of gluon modifications in a wide pseudorapidity interval. The sensitivity is greatly enhanced at LHC (Large Hadron Collider) energies relative to that at RHIC (Relativistic Heavy Ion Collider). The charge ratio is mildly sensitive only at large Bjorken x. Thus measurement of these observables in proton-lead collisions at the LHC affords the potential to further constrain gluon modifications in global fits.