  We propose to build and operate a detector that, for the first time, will
measure the process $pp\to\nu X$ at the LHC and search for feebly interacting
particles (FIPs) in an unexplored domain. The TI18 tunnel has been identified
as a suitable site to perform these measurements due to very low
machine-induced background. The detector will be off-axis with respect to the
ATLAS interaction point (IP1) and, given the pseudo-rapidity range accessible,
the corresponding neutrinos will mostly come from charm decays: the proposed
experiment will thus make the first test of the heavy flavour production in a
pseudo-rapidity range that is not accessible by the current LHC detectors. In
order to efficiently reconstruct neutrino interactions and identify their
flavour, the detector will combine in the target region nuclear emulsion
technology with scintillating fibre tracking layers and it will adopt a muon
identification system based on scintillating bars that will also play the role
of a hadronic calorimeter. The time of flight measurement will be achieved
thanks to a dedicated timing detector. The detector will be a small-scale
prototype of the scattering and neutrino detector (SND) of the SHiP experiment:
the operation of this detector will provide an important test of the neutrino
reconstruction in a high occupancy environment.
