  We have carried out $\nu_{\mu}$ charged-current interaction measurement on
iron using an emulsion detector exposed to the T2K neutrino beam in the J-PARC
neutrino facility. The data samples correspond to 4.0$\times$10$^{19}$ protons
on target, and the neutrino mean energy is 1.49$\,$GeV. The emulsion detector
is suitable for precision measurements of charged particles produced in
neutrino-iron interactions with a low momentum threshold thanks to thin-layered
structure and sub-$\mu$m spatial resolution. The charged particles are
successfully detected, and their multiplicities are measured using the emulsion
detector. The cross section was measured to be
$\sigma^{\mathrm{Fe}}_{\mathrm{CC}} = (1.28 \pm
0.11({\mathrm{stat.}})^{+0.12}_{-0.11}({\mathrm{syst.}})) \times 10^{-38} \,
{\mathrm{cm}}^{2}/{\mathrm{nucleon}}$. The cross section in a limited kinematic
phase space of induced muons, $\theta_{\mu} < 45^{\circ}$ and $p_{\mu} > 400 \,
{\rm MeV}/c$, on iron was $\sigma^{\mathrm{Fe}}_{\mathrm{CC \hspace{1mm} phase
\hspace{0.5mm} space}} = (0.84 \pm
0.07({\mathrm{stat.}})^{+0.07}_{-0.06}({\mathrm{syst.}})) \times 10^{-38} \,
{\mathrm{cm}}^{2}/{\mathrm{nucleon}}$. The cross-section results are consistent
with previous values obtained via different techniques using the same beamline,
and they are well reproduced by current neutrino interaction models. These
results demonstrate the capability of the detector towards the detailed
measurements of the neutrino-nucleus interactions around the 1$\,$GeV energy
region.

High Energy Physics - Experiment