Elliptic flow of charm and strange hadrons in high-multiplicity pPb collisions at $sqrts__mathrmNN =$ 8.16 TeV

The elliptic azimuthal anisotropy coefficient ($v_2$) is measured for charm (D$^0$) and strange (K$_mathrmS^0$, $Lambda$, $\Xi^-$, and $Omega^-$) hadrons, using a data sample of pPb collisions collected by the CMS experiment, at a nucleon-nucleon center-of-mass energy $sqrts__mathrmNN =$ 8.16 TeV. A significant positive $v_2$ signal from long-range azimuthal correlations is observed for all particle species in high-multiplicity pPb collisions. The measurement represents the first observation of possible long-range collectivity for open heavy flavor hadrons in small systems. The results suggest that charm quarks have a smaller $v_2$ than the lighter quarks, probably reflecting a weaker collective behavior. This effect is not seen in the larger PbPb collision system at $sqrts__mathrmNN =$ 5.02 TeV, also presented.