Measurements of Proton High-Order Cumulants in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>3</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>GeV</mml:mi></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Au</mml:mi><mml:mo>+</mml:mo><mml:mi>Au</mml:mi></mml:mrow></mml:math> Collisions and Implications for the QCD Critical Point
M. S. Abdallah, B. E. Aboona, J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, S. S. Shi, I. Aggarwal, M. M. Aggarwal, Z. Ahammed, I. Alekseev, D. M. Anderson, A. Aparin, E. C. Aschenauer, M. U. Ashraf, F. G. Atetalla, A. Attri, G. S. Averichev, V. Bairathi, W. Baker, J. Ball, K. N. Barish, A. Behera, R. Bellwied, P. Bhagat, A. Bhasin, J. Bielcik, J. Bielcikova, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, I. Bunzarov, X. Z. Cai, H. Caines, M. Calderon De La Barca Sanchez, D. Cebra, I. Chakaberia, P. Chaloupka, B. K. Chan, F-H. Chang, Z. Chang, N. Chankova-Bunzarova, A. Chatterjee, S. Chattopadhyay, D. Chen, J. Chen, J. H. Chen, X. Chen, Z. Chen, J. Cheng, M. Chevalier, S. Choudhury, W. Christie, X. Chu, H. J. Crawford, M. Csanád, M. Daugherity, Т. Г. Дедович, I. M. Deppner, A. A. Derevschikov, A. Dhamija, L. Di Carlo, L. Didenko, P. Dixit, X. Dong, J. L. Drachenberg, E. Duckworth, J. C. Dunlop, N. Elsey, J. Engelage, G. Eppley, S. Esumi, O. Evdokimov, A. Ewigleben, O. Eyser, R. Fatemi, F. M. Fawzi, S. Fazio, P. Federic, J. Fedorisin, C. Feng, Yuliang Feng, P. Filip, E. Finch, Y. Fisyak, A. Francisco, C. Fu, Ł. Fulek, C. A. Gagliardi, T. Galatyuk, F. J. M. Geurts, N. Ghimire, S. M. Gibson, K. Gopal, X. Gou, D. Grosnick, A. Gupta, W. Guryn, A. I. Hamad, A. Hamed
Abstract
We report cumulants of the proton multiplicity distribution from dedicated fixed-target $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=3.0\text{ }\text{ }\mathrm{GeV}$, measured by the STAR experiment in the kinematic acceptance of rapidity ($y$) and transverse momentum (${p}_{T}$) within $\ensuremath{-}0.5<y<0$ and $0.4<{p}_{T}<2.0\text{ }\text{ }\mathrm{GeV}/c$. In the most central 0%--5% collisions, a proton cumulant ratio is measured to be ${C}_{4}/{C}_{2}=\ensuremath{-}0.85\ifmmode\pm\else\textpm\fi{}0.09\text{ }(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.82\text{ }(\mathrm{syst})$, which is $2\ensuremath{\sigma}$ 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.