Observation of prompt J/psi meson elliptic flow in high-multiplicity pPb collisions at sqrt(s_NN) = 8.16 TeV

A measurement of the elliptic flow (v 2 ) of prompt J/ψ mesons in high-multiplicity pPb collisions is reported using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy s NN =8.16TeV. 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.