CERN Accelerating science

Schematic side view of the FASER detector with a muon neutrino undergoing a CC interaction in the emulsion-tungsten target.

The selected signal region in extrapolated radius $r_{\mathrm{veto}\, \nu}$ and reconstructed track momentum $p_\mu$ is depicted. The region with lower momenta and larger radii is dominated by background events consisting of charged particles that miss the FASER$\nu$ scintillator station.

Extrapolated transverse position of the reconstructed tracks of neutrino-like events to the FASER$\nu$ scintillator station. The ATLAS LOS is indicated with a red marker and shifted \SI{59}{\milli\meter} in the negative $y$ direction from the center of the scintillator station.

The figures depict the number of reconstructed clusters in the IFT, track polar angle $\theta_\mu$, $q/p_\mu$, and the reconstructed momentum $p_\mu$ for events in the signal region (black markers) and compare them to the expectation from \texttt{GENIE} (blue) and muon-like events (grey markers). The muon-like events are from the $n_2$ category, for which both layers of the FASER$\nu$ scintillator observed a signal, and show the expected distributions for non-neutrino backgrounds. The blue bands correspond to the statistical error of the simulated samples and are luminosity scaled for $q/p_\mu$ and $p_\mu$. The other figures are normalized to unity.

The figures depict the number of reconstructed clusters in the IFT, track polar angle $\theta_\mu$, $q/p_\mu$, and the reconstructed momentum $p_\mu$ for events in the signal region (black markers) and compare them to the expectation from \texttt{GENIE} (blue) and muon-like events (grey markers). The muon-like events are from the $n_2$ category, for which both layers of the FASER$\nu$ scintillator observed a signal, and show the expected distributions for non-neutrino backgrounds. The blue bands correspond to the statistical error of the simulated samples and are luminosity scaled for $q/p_\mu$ and $p_\mu$. The other figures are normalized to unity.

The figures depict the number of reconstructed clusters in the IFT, track polar angle $\theta_\mu$, $q/p_\mu$, and the reconstructed momentum $p_\mu$ for events in the signal region (black markers) and compare them to the expectation from \texttt{GENIE} (blue) and muon-like events (grey markers). The muon-like events are from the $n_2$ category, for which both layers of the FASER$\nu$ scintillator observed a signal, and show the expected distributions for non-neutrino backgrounds. The blue bands correspond to the statistical error of the simulated samples and are luminosity scaled for $q/p_\mu$ and $p_\mu$. The other figures are normalized to unity.

The figures depict the number of reconstructed clusters in the IFT, track polar angle $\theta_\mu$, $q/p_\mu$, and the reconstructed momentum $p_\mu$ for events in the signal region (black markers) and compare them to the expectation from \texttt{GENIE} (blue) and muon-like events (grey markers). The muon-like events are from the $n_2$ category, for which both layers of the FASER$\nu$ scintillator observed a signal, and show the expected distributions for non-neutrino backgrounds. The blue bands correspond to the statistical error of the simulated samples and are luminosity scaled for $q/p_\mu$ and $p_\mu$. The other figures are normalized to unity.

Sideband for geometric background estimation.

Event display of a neutrino interaction candidate in which secondary particles produced in the CC interaction produce activity in the IFT.

The log-likelihood ratio of the estimated number of neutrinos is shown in blue. The dashed orange contour fixes the parameters of $\mathcal{G}_i$ to determine the statistical uncertainty of the neutrino signal yield.