Measurement of the muon flux at the SND@LHC experiment

The Scattering and Neutrino Detector at the LHC (\SND) is a compact standalone experiment, which started taking data at the beginning of Run 3 of the LHC. The experiment is designed to perform measurements with neutrinos produced in proton-proton collisions at the LHC in an energy range between~100~GeV and~1~TeV, and a previously unexplored pseudo-rapidity range of \mbox{$7.2<\eta<8.4$}. The detector, located 480~m downstream of the ATLAS interaction point in the TI18 tunnel, comprises a veto system followed by an 830~kg target mass consisting of tungsten plates, interleaved with nuclear emulsion plates and Scintillating Fiber (SciFi) electronic trackers, and then a calorimeter and a downstream muon system (DS). The measurement of the muon flux in the TI18 tunnel using the nuclear emulsion tracker and the electronic detectors, SciFi tracker and downstream muon detector, is reported here. The muon flux per integrated luminosity through an \mbox{18$\times$18 cm$^{2}$} area in the emulsions is \mbox{$1.5 \pm 0.1(\textrm{stat}) \times 10^4\,\textrm{fb/cm}^{2}$}. The measured muon flux per integrated luminosity through a \mbox{31$\times$31 cm$^{2}$} central SciFi area is\\ \centerline{\mbox{$2.06\pm0.01(\textrm{stat})\pm0.11(\textrm{sys}) \times 10^{4}\,\textrm{fb/cm}^{2}$},} while for the downstream muon system the flux is\\ \centerline{\mbox{$2.35\pm0.01(\textrm{stat})\pm0.08(\textrm{sys}) \times 10^{4}\,\textrm{fb/cm}^{2}$}} for a \mbox{52$\times$52 cm$^{2}$} central detector region. The total relative uncertainty of the electronic detectors measurements is 5~$\%$ for the SciFi and 3~$\%$ for the DS measurement. The Monte Carlo simulation prediction of these fluxes is~20-25~$\%$ lower than the measured values.}