Symmetric-asymmetric collision comparison: disentangling nuclear structure and subnucleonic structure effects for small system flow

TL;DR

This study uses Glauber models to compare symmetric O+O collisions with asymmetric small systems, aiming to separate effects of nuclear and subnucleonic structures on flow observables in small collision systems.

Contribution

It introduces a method to disentangle nuclear and subnucleonic effects using symmetric and asymmetric collision comparisons with Glauber models.

Findings

Subnucleonic fluctuations affect O+O collisions uniquely.

Flow observable patterns can distinguish nuclear from subnucleonic contributions.

Comparison reduces uncertainties in initial conditions for small system studies.

Abstract

Previous flow measurements in small collision systems were mostly based on highly asymmetric collisions ($p$+Pb, $p$+Au, $d$+Au, $^{3}$He+Au), where both nuclear structure and subnucleonic fluctuations are important. Comparing these asymmetric systems with the newly available symmetric $^{16}$O+$^{16}$O collisions at RHIC and LHC provides a unique opportunity to disentangle these two contributions. Using Glauber models incorporating both nucleon and quark-level substructure, we analyze multiplicity distributions and initial-state estimators: eccentricities $\varepsilon_n$ for anisotropic flow $v_n$ and inverse transverse size $d_{\perp}$ for radial flow. We find that subnucleonic fluctuations impact O+O collisions differently from asymmetric systems, creating specific patterns in flow observables that enable disentangling the competing contributions. Such experimental comparisons will reduce uncertainties in the initial conditions and improve our understanding of the properties of the QGP-like medium produced in small systems.