# CMS observes top quarks in proton-nucleus collisions !

On Monday, 18th of September, at the 10th International Workshop on Top Quark Physics, TOP 2017, in Braga, Portugal, the CMS experiment reported the first observation of the top pair (tt) production using proton-nucleus collisions at 8.16 TeV center-of-mass (c.o.m) energy. The excess of events with respect to the background-only hypothesis corresponds to a significance of more than 5σ (the conventional “golden standard” for observation) even under the most conservative assumptions. The measured top-pair cross section is consistent with the expectations from the scaled proton-proton data as well as pQCD predictions at next-to-next-to-leading order with next-to-next-to-leading-log accuracy.