  There is an increasing scientific and technological interest on the design
and implementation of nanoscale sources of quantum light. Here, we investigate
the quantum statistics of the light scattered from a plasmonic nanocavity
coupled to a mesoscopic ensemble of emitters under low coherent pumping. We
present an analytical description of the intensity correlations taking place in
these systems, and unveil the fingerprint of plasmon-exciton-polaritons in
them. Our findings reveal that plasmonic cavities are able to retain and
enhance excitonic nonlinearities even when the number of emitters is large.
This makes plasmonic strong coupling a promising route for generating
nonclassical light beyond the single emitter level.
