Accessing subnuclear fluctuations and saturation with multiplicity dependent J/ψ production in p plus p and p plus Pb collisions

We study the production of J/psi vector mesons as a function of charged hadron multiplicity in p+p and p+Pb collisions at LHC energies. We employ the color glass condensate framework, using running coupling Balitsky-Kovchegov evolved dipole amplitudes, to compute gluon and c (c) over bar -pair production. We use fragmentation functions to obtain charged hadrons, and explore two different hadronization schemes for the J/psi: non-relativistic quantum chromodynamics and the improved color evaporation model. In our framework, event-by-event multiplicity fluctuations of both hadrons and J/psi are driven by geometric and saturation scale normalization fluctuations. Studying the correlation between J/psi and hadron multiplicity, we show that the characteristic difference between forward and backward rapidity in p+Pb collisions is a result of different degrees of saturation probed at different rapidities. We demonstrate that experimental data on heavy-flavor production as a function of event activity provide stringent constraints on the fluctuating proton structure. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).

Automated summary

This study investigates the relationship between the production of J/psi vector mesons and the charged hadron multiplicity in p+p and p+Pb collisions at LHC energies. The research demonstrates that the characteristic difference between forward and backward rapidity in p+Pb collisions is due to different degrees of saturation probed at different rapidities. The study also shows that experimental data on heavy-flavor production as a function of event activity provide stringent constraints on the fluctuating proton structure.