Speakers
Description
The search for sterile neutrinos is a central goal of the Short-Baseline Neutrino program at Fermilab. It aims to definitively test the anomalies reported by LSND and MiniBooNE, which may hint at oscillations involving additional neutrino species beyond the three active flavours of the Standard Model. ICARUS-T600 is the far detector of the SBN program and operates as a Liquid Argon Time Projection Chamber or LArTPC, offering high-resolution imaging of neutrino interactions.
A key challenge in SBN physics is the accurate reconstruction of the muon momentum in $ν_μ$ CC events. In the energy range of 0–3 GeV, relevant to the Booster Neutrino Beam, many muons exit the active volume. For such uncontained muons, standard momentum estimation methods such as range-based and calorimetry are not applicable. In these cases, the only viable technique is based on Multiple Coulomb Scattering (MCS). MCS relies on the fact that charged particles undergo angular deflections when traversing a medium, due to interactions with the Coulomb field of atomic nuclei. The RMS of these deflections is inversely related to the particle momentum and depends on the material and the track segment length. In a LArTPC, these deflections can be measured from the spatial reconstruction of hits along the track.
This analysis involves two algorithms. The “Gran Sasso” algorithm was originally developed for ICARUS operations at Gran Sasso and exploits both 2D scattering angles measured in the three reconstruction planes and 3D scattering angles to perform a chi-squared fit of the track segments. The “MicroBooNE” algorithm, originally developed by the MicroBooNE collaboration, relies exclusively on 3D scattering angles and uses instead a likelihood-based approach. Both algorithms compare the observed angular deflections with the expected distribution for a given momentum hypothesis, aiming to extract the most probable momentum for each track while accounting for the varying scattering along the trajectory.
These two algorithms have been tested on simulated and real stopping muons in the range 0.4–1 GeV/c, using the range momentum as a benchmark. The performance is quantified in terms of bias, which represents the deviation of the reconstructed momentum from the benchmark value, and resolution, which reflects the spread of reconstructed values around the range momentum. Current studies indicate that, at low momenta, a residual bias of approximately 10% remains, while the resolution reaches 15–20%.
Despite these limitations, these MCS-based techniques are crucial, as they allow the recovery of momentum information for muons exiting the detector, increasing the available statistics for $ν_μ$ CC analyses by a factor of two. In fact, the improved reconstruction of uncontained muons enhances the sensitivity of the SBN program to $ν_μ$ disappearance and to potential signals of sterile neutrino oscillations in the 3+1 framework. This work represents an important step in maximizing the physics reach of ICARUS-T600 and in validating the applicability of MCS techniques in large LArTPC detectors, paving the way for future high-precision neutrino measurements.
Finally, with an improved sample of reconstructed muons, ICARUS-T600 can perform precision studies of $ν_μ$ oscillation parameters, searching for deviations from the Standard Model predictions. This includes exploring Beyond Standard Model physics scenarios such as sterile neutrino-induced oscillations, non-standard neutrino interactions, or exotic decay modes, thereby broadening the experimental sensitivity of the SBN program beyond the original sterile neutrino search.