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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 ¹⁶O + ¹⁶O data with collisions of ²⁰Ne ions. We couple both nuclear lattice effective field theory (NLEFT) and projected generator coordinate method (PGCM) abmore » initio descriptions of the structure of ²⁰Ne and ¹⁶O to hydrodynamic simulations of ¹⁶O + ¹⁶O and ²⁰Ne + ²⁰Ne 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 ²⁰Ne + ²⁰Ne collisions is enhanced by as much as 1.174⁢(8)_stat⁢(31)_syst for NLEFT and 1.139⁢(6)_stat⁢(39)_syst for PGCM relative to ¹⁶O + ¹⁶O 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.« less

The System for Measuring Overlap with Gas (SMOG2) at the LHCb detector enables the study of fixed-target ion-ion collisions at relativistic energies ($$\sqrt{𝑠_{NN}}$$ ∼ 100 GeV in the center of mass). Here, with input from ab initio calculations of the structure of ¹⁶O and ²⁰Ne , we compute 3+1⁢D hydrodynamic predictions for the anisotropic flow of Pb+Ne and Pb+O collisions to be tested with upcoming LHCb data. This will allow the detailed study of quark-gluon plasma formation as well as experimental tests of the predicted nuclear shapes. Elliptic flow (𝑣₂) in Pb + Ne collisions is greatly enhanced compared tomore » the Pb + O baseline due to the shape of ²⁰Ne , which is deformed in a bowling-pin geometry. Owing to the large ²⁰⁸Pb radius, this effect is seen in a broad centrality range, a unique feature of this collision configuration. Larger elliptic flow further enhances the quadrangular flow (𝑣₄) of Pb + Ne collisions via nonlinear coupling, and impacts the sign of the kurtosis of the elliptic flow vector distribution (𝑐₂⁡{4}). Exploiting the shape of ²⁰Ne proves thus an ideal method to investigate the formation of quark-gluon plasma in fixed-target experiments at LHCb, and demonstrates the power of System for Measuring Overlap with Gas as a tool to image nuclear ground states.« less