Measurements of Proton High-Order Cumulants in √sNN=3 GeV Au + Au Collisions and Implications for the QCD Critical Point

作者：Abdallah, M. S.; Aboona, B. E.; Adam, J.; Adamczyk, L.; Adams, J. R.; Adkins, J. K.; Agakishiev, G.; Aggarwal, I; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I; Anderson, D. M.; Aparin, A.; Aschenauer, E. C.; Ashraf, M. U.; Atetalla, F. G.; Attri, A.; Averichev, G. S.; Bairathi, V; Baker, W.; Cap, J. G. Ball; Barish, K.; Behera, A.; Bellwied, R.; Bhagat, P.; Bhasin, A.; Bielcik, J.; Bielcikova, J.; Bordyuzhin, I. G.; Brandenburg, J. D.; Brandin, A., V; Bunzarov, I; Cai, X. Z.; Caines, H.

来源：Physical Review Letters, 2022, 128(20): 202303.

DOI：10.1103/PhysRevLett.128.202303

• FREEZE-OUT CONDITIONS
• FLUCTUATIONS
• COLLISIONS
• QCD
• PERSPECTIVE

We report cumulants of the proton multiplicity distribution from dedicated fixed-target Au + Au collisions at root s(NN) = 3.0 GeV, measured by the STAR experiment in the kinematic acceptance of rapidity (y) and transverse momentum (p(T)) within -0.5 < y < 0 and 0.4 < p(T) < 2.0 GeV/c. In the most central 0%-5% collisions, a proton cumulant ratio is measured to be C-4/C-2 = -0.85 +/- 0.09 (stat) +/- 0.82 (syst), which is 2 sigma below the Poisson baseline with respect to both the statistical and systematic uncertainties. The hadronic transport UrQMD model reproduces our C-4/C-2 in the measured acceptance. Compared to higher energy results and the transport model calculations, the suppression in C-4/C-2 is consistent with fluctuations driven by baryon number conservation and indicates an energy regime dominated by hadronic interactions. These data imply that the QCD critical region, if created in heavy-ion collisions, could only exist at energies higher than 3 GeV.