Hidden Heavy Flavor

J/psi suppression was one of the proposed QGP signatures in the early days. Later, various cold nuclear matter effects were brought up to complicate the interpretation of J/psi measurements. Still, the study of J/psi collective motion deepens our understanding of the coalescence mechanism and the charm quark collectivity. We also reconstructed Upsilon and observed the suppression of Upsilon(1S+2S+3S).