Observation of prompt J/ψ meson elliptic flow in high-multiplicity pPb collisions at sNN=8.16 TeV

Abstract A measurement of the elliptic flow ( v 2 ) of prompt J / ψ mesons in high-multiplicity p Pb  collisions is reported using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy s NN = 8.16 TeV . Prompt J / ψ mesons decaying into two muons are reconstructed in the rapidity region in the nucleon-nucleon center-of-mass frame ( y cm ), corresponding to either − 2.86 y cm − 1.86 or 0.94 y cm 1.94 . The average v 2 result from the two rapidity ranges is reported over the transverse momentum ( p T ) range from 0.2 to 10 GeV. Positive v 2 values are observed for the prompt J / ψ meson, as extracted from long-range two-particle correlations with charged hadrons, for 2 p T 8  GeV. The prompt J / ψ results are compared with previous CMS measurements of elliptic flow for open charm mesons ( D 0 ) and strange hadrons. From these measurements, constraints can be obtained on the collective dynamics of charm quarks produced in high-multiplicity events arising from small systems.