  The T2K near-detector, ND280, employs three large argon gas TPCs (Time
Projection Chambers) for particle tracking and identification. The gas inside
the TPCs can be used as an active target to study the neutrino interactions in
great detail. The low density of the gas leads to very low track energy
thresholds, allowing the reconstruction of very low momentum tracks, e.g.
protons with kinetic energies down to $\mathcal{O}$(1 MeV). Since different
nuclear interaction models vary considerably in their predictions of those low
momentum track multiplicities, this makes neutrino interactions on gases a
powerful probe to test those models. The TPCs operate with an argon-based gas
mixture (95% by volume) and have been exposed to the T2K neutrino beam since
the beginning of the experiment in 2010. Due to the low total mass of the gas,
neutrino argon interactions happen only rarely, compared to the surrounding
scintillator-based detectors. We expect about 600 such events in the recorded
data so far (about 200 in the fiducial volume). We are able to separate those
events from the background and thus demonstrate the viability of using gaseous
argon as a target for a neutrino beam. This enables us to do a cross- section
measurement on gaseous argon, the first measurement of this kind. All previous
neutrino cross-section measurements on argon were performed in liquid argon
TPCs.
