Wounded quarks in A+A, p+A, and p+p collisions

TL;DR

This paper applies the wounded quark model to predict particle production and initial state properties in various high-energy collisions, showing close agreement with nucleon-based models and providing insights into subnucleonic effects at LHC energies.

Contribution

The study extends the wounded quark model to A+A, p+A, and p+p collisions, incorporating subnucleonic degrees of freedom and analyzing their impact on initial state predictions.

Findings

Wounded quark predictions are within 15% of wounded nucleon model for eccentricities and sizes.

Wounded quark model predicts a more compact initial fireball in p+Pb collisions.

Particle production per wounded quark is approximately uniform across different collision systems at LHC energies.

Abstract

We explore predictions of the wounded quark model for particle production and properties of the initial state formed in ultrarelativistic heavy-ion collisions. The approach is applied uniformly to A+A collisions in a wide collision energy range, as well as for p+A and p+p collisions at the CERN Large Hadron Collider (LHC). We find that generically the predictions from wounded quarks for such features as eccentricities or initial sizes are close (within 15\%) to predictions of the wounded nucleon model with an amended binary component. A larger difference is found for the size in p+Pb system, where the wounded quark model yields a smaller (more compact) initial fireball than the standard wounded nucleon model. The inclusion of subnucleonic degrees of freedom allows us to analyze p+p collisions in an analogous way, with predictions that can be used in further collective evolution. The approximate linear dependence of particle production in A+A collisions on the number of wounded quarks, as found in previous studies, makes the approach based on wounded quarks natural. Importantly, at the LHC energies we find approximate uniformity in particle production from wounded quarks, where at a given collision energy per nucleon pair similar production of initial entropy per source is needed to explain the particle production from p+p collisions up to A+A collisions. We also discuss the sensitivity of the wounded quark model predictions to distribution of quarks in nucleons, distribution of nucleons in nuclei, and to the quark-quark inelasticity profile in the impact parameter. In our procedure, the quark-quark inelasticity profile is chosen in such a way that the experiment-based parametrization of the proton-proton inelasticity profile is properly reproduced. The parameters of the overlaid multiplicity distribution is fixed from p+p and p+Pb data.