Speaker
Description
In the search for the conjectured QCD critical point, higher-order cumulants of conserved quantities have been proposed as sensitive observables and have been studied extensively, both experimentally and theoretically. Recently, a precision measurement [1] of net-proton number fluctuations by the STAR Collaboration was published, focusing on high-statistics Au+Au collision datasets at $\sqrt{s_{NN}}$ = 7.7-27 GeV from the RHIC Beam Energy Scan II program. The measured net-proton $C_{4}/C_{2}$ ratio exhibits a minimum around 19.6 GeV relative to non-critical baselines, which is expected to be a characteristic signature of the QCD critical point. However, a comprehensive measurement of the collision energy dependence, especially at lower energies $\sqrt{s_{NN}} < $7.7 GeV, is needed to establish the existence of the critical point.
In this talk, we present new measurements of (net-)proton fluctuations in Au+Au collisions at $\sqrt{s_{NN}}$ = 3.0-27 GeV using a centrality-dependent method [2]. We compare our results with transport model calculations and discuss the physics implications regarding the QCD critical point.
[1] B. E. Aboona et al. (STAR), Precision Measurement of Net-Proton-Number Fluctuations in Au+Au Collisions at RHIC, \href{https://doi.org/10.1103/9l69-2d7p}{Phys. Rev. Lett. 135, 142301 (2025)}
[2] Z. Wang and X. Luo, A centrality-independent framework for revealing genuine higher-order cumulants in heavy-ion collisions, \href{https://doi.org/10.1016/j.physletb.2025.139984}{Physics Letters B 871, 139984 (2025)}
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