CMS-PAS-HIN-21-010

CMS-PAS-HIN-21-010
Probing hydrodynamics and the moments of the elliptic flow distribution in ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}=$ 5.02 TeV lead-lead collisions using higher-order cumulants
CMS Collaboration
April 2022

Abstract: The $v_{2}$ cumulant values for the elliptic anisotropy harmonic, $v_{2}\{2k\}$ , are determined up to the tenth order ( $k = 5$ ) as a function of the collision centrality in ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}=$ 5.02 TeV lead-lead collisions. The data were obtained by the CMS experiment at the LHC. A fine splitting is observed for the coefficients, with $v_{2}\{2\} > v_{2}\{4\} \gtrsim v_{2}\{6\} \gtrsim v_{2}\{8\} \gtrsim v_{2}\{10\}$ . The subtle differences in the higher order harmonics allow for a precise determination of the underlying hydrodynamics. Based on these results, centrality-dependent moments for the fluctuation-driven $v_{2}$ distribution are determined, including the skewness, the kurtosis and, for the first time, the superskewness. Assuming a hydrodynamic expansion of the produced medium, these moments directly probe the initial state geometry in high energy nuclear collisions.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to JHEP. The superseded preliminary plots can be found here.

CMS Publications