Theoretical Modeling of J/psi Yield Modifications in Proton (Deuteron) - Nucleus Collisions at High Energy

TL;DR

This paper investigates the limitations of current theoretical models, including nuclear-modified PDFs and coherence effects, in explaining J/psi yield modifications in high-energy proton and deuteron-nucleus collisions, highlighting the need for additional physics mechanisms.

Contribution

The study extends existing models to explore geometric dependencies and compares them with new experimental data, revealing their inability to fully describe observed J/psi modifications.

Findings

Current models cannot simultaneously fit rapidity and centrality dependence.

Coherence calculations also fail to match the data.

Additional physics mechanisms like initial-state energy loss are needed.

Abstract

Understanding the detailed production and hadronization mechanisms for heavy quarkonia and their modification in a nuclear environment presents one of the major challenges in QCD. Calculations including nuclear-modified parton distribution functions (nPDFs) and fitting of break-up cross sections (sigma_breakup) as parameters have been successful at describing many features of J/psi modification in proton(deuteron)-nucleus collisions. In this paper, we extend these calculations to explore different geometric dependencies of the modification and confront them with new experimental results from the PHENIX experiment. We find that no combination of nPDFs and sigma_breakup, regardless of the nPDF parameter set and the assumed geometric dependence, can simultaneously describe the entire rapidity and centrality dependence of J/psi modifications in d+Au collisions at sqrt(s_NN) = 200 GeV. We also compare the data with coherence calculations and find them unable to describe the full rapidity and centrality dependence as well. We discuss how these calculations might be extended and further tested, in addition to discussing other physics mechanisms including initial-state parton energy loss.