First search for neutrino-induced charm hadrons with FASER's emulsion detector at the LHC

This note presents the first search for charmed-hadron production in high-energy electron and muon neutrino charged-current interactions in the FASER$\nu$ emulsion--tungsten detector at the LHC. Dedicated tools for reconstructing displaced secondary vertices and classifying decay topologies of charged charm hadrons have been developed and validated using Monte Carlo simulation. A multivariate analysis using Lorentz-invariant kinematical parameters is employed to discriminate charm hadron decays from hadronic interaction backgrounds. The analysis is applied to 40 neutrino interaction candidates identified in 9.5~fb$^{-1}$ of $pp$ collision data at $\sqrt{s} = 13.6$ TeV collected during 2022, and good agreement between data and simulation is observed for the secondary vertex properties.