The unexpected uses of a bowling pin: exploiting ²⁰Ne isotopes for precision characterizations of collectivity in small systems

Whether or not femto-scale droplets of quark-gluon plasma (QGP) are formed in so-called small systems at high-energy colliders is a pressing question in the phenomenology of the strong interaction. For proton-proton or proton-nucleus collisions the answer is inconclusive due to the large theoretical uncertainties plaguing the description of these processes. While upcoming data on collisions of ¹⁶O nuclei may mitigate these uncertainties in the near future, here we demonstrate the unique possibilities offered by complementing ¹⁶O¹⁶O data with collisions of ²⁰Ne ions. We couple both NLEFT and PGCM ab initio descriptions of the structure of ²⁰Ne and ¹⁶O to hydrodynamic simulations of ¹⁶O¹⁶O and ²⁰Ne²⁰Ne collisions at high energy. We isolate the imprints of the bowling-pin shape of ²⁰Ne on the collective flow of hadrons, which can be used to perform quantitative tests of the hydrodynamic QGP paradigm. In particular, we predict that the elliptic flow of ²⁰Ne²⁰Ne collisions is enhanced by as much as 1.170(8)stat.(30)syst. for NLEFT and 1.139(6)stat.(39)syst. for PGCM relative to ¹⁶O¹⁶O collisions for the 1% most central events. At the same time, theoretical uncertainties largely cancel when studying relative variations of observables between two systems. This demonstrates a method based on experiments with two light-ion species for precision characterizations of the collective dynamics and its emergence in a small system.