Charged Particle and Proton Multiplicity in MicroBooNE

We study charged current neutrino-argon interactions that have at least two long tracks, one consistent with a muon and other consistent with a pion or proton, recorded in the MicroBooNE detector operated in Fermilab's Booster Neutrino Beam. These events typically have two well-reconstructed tracks that can be used to determine the location of the neutrino-argon interaction vertex in a manner that is largely independent of the presence of other final state objects in the event. We then obtain the charged particle and proton multiplicity distributions for the cases where the two long tracks form a muon-pion pair or where they form a muon-proton pair, and we compare these multiplicity distributions to predictions. The measurements test models of hadron production in neutrino-argon interactions in a semi-inclusive fashion, including, potentially, low energy proton production from final state interactions within the argon nucleus.