The ENUBET Monitored Neutrino Beam for High Precision Cross-Section Measurements

The main source of systematic uncertainty on neutrino cross-section measurements at the GeV scale originates from the poor knowledge of the initial flux. The goal of reducing this uncertainty to 1% can be achieved through the monitoring of charged leptons produced in association with neutrinos, by properly instrumenting the decay region of a conventional narrow-band neutrino beam. Large-angle muons and positrons from kaons are measured by a sampling calorimeter on the decay tunnel walls, while muon stations after the hadron dump can be used to monitor the neutrino component from pion decays. Furthermore, the narrow momentum width (<10%) of the beam provides a O (10%) measurement of the neutrino energy on an event-by-event basis, thanks to its correlation with the radial position of the interaction at the neutrino detector. The ENUBET project has been funded by the ERC in 2016 to prove the feasibility of such a monitored neutrino beam and, since 2019, ENUBET is also a CERN neutrino platform experiment (NP06/ENUBET). The breakthrough the project achieved is the design of a horn-less neutrino beamline that would allow for a 1% measurement of 𝜈𝑒 and 𝜈𝜇 cross-sections in about 3 years of data taking at CERN-SPS, using ProtoDUNE as far detector.