Speaker
Description
The charged-current interaction of a muon neutrino with a strange (or down) sea quark, followed by the semileptonic decay of the resulting charmed meson, can produce a characteristic opposite-sign dimuon final state. This Standard Model process was exploited at fixed-target and beam-dump neutrino experiments to measure the strange-quark content of the nucleon and the charm production cross section at neutrino energies of ~10–500 GeV. Despite atmospheric-neutrino data now accumulated at the GeV–TeV scale, the channel has never been directly observed in a neutrino telescope, leaving a well-understood Standard Model process unmeasured in a laboratory uniquely suited to it.
We present a feasibility and sensitivity study aimed at closing that gap, using the KM3NeT/ORCA-18 partial detector configuration in the Mediterranean Sea. Dedicated Monte Carlo of charm-induced νμ charged-current interactions is produced and passed through the full KM3NeT simulation, triggering, and event-reconstruction pipeline. A custom two-muon likelihood fitter reconstructs both muons simultaneously; its output and standard reconstruction observables feed a multivariate classifier that separates dimuon events from the single-muon νμ CC background.
At the expected atmospheric flux, the analysis predicts approximately 35 signal events per year over a background of ~4150 events per year. A binned likelihood fit to the classifier-score distribution projects 3σ evidence for the charm-dimuon signal at its Standard Model-predicted rate in approximately 23 years of ORCA-18 live time, and a 5σ discovery in approximately 63 years. Assuming linear scaling with instrumented volume, the full 115-line KM3NeT/ORCA detector reduces these timescales to approximately 4 and 10 years respectively, bringing the first direct observation of charm production in neutrino-nucleon scattering at a neutrino telescope well within the operating lifetime of the full instrument.
An extension of this programme to the high-energy KM3NeT/ARCA sub-detector, where the charm production cross section in neutrino-nucleon scattering has never been directly measured, is under active investigation.
