Interest in these types of high precision neutrino beams has grown significantly in the last ten years,[3] especially after the start of the construction of the DUNE and Hyper-Kamiokande detectors.
DUNE and Hyper-Kamiokande are aimed at discovering CP violation in neutrinos observing a small difference between the probability of a muon-neutrino to oscillate into an electron-neutrino and the probability of a muon-antineutrino to oscillate into an electron-antineutrino.
This effect points toward a difference in the behavior of matter and antimatter.
In quantum field theory, this effect is described by a violation of the CP symmetry in particle physics.
A new generation of cross-section experiment is therefore needed to overcome these limitations with new techniques or high precision beams, as ENUBET.
[5][6] In ENUBET, neutrinos are produced by focusing mesons in a narrow band beam towards an instrumented decay tunnel, where charged leptons produced in association with neutrinos by mesons' decay can be monitored at the single particle level.
Mesons (essentially pions and kaons) are produced in the interactions of accelerated protons with a Beryllium or Graphite target.
Kaons and pions are momentum and charge selected in a short transfer line by means of dipole and quadrupole magnets and are focused in a collimated beam into an instrumented decay tube.
Large angle muons and positrons from kaon decays (
) are measured by detectors on the tunnel walls, while muons from pion decays (
In this way, the neutrino flux is assessed in a direct way with a precision of 1%, without relying on complex simulations of the transfer line and on hadro-production data extrapolation that currently limits the knowledge of the flux to 5-10%.
This method can also be extended to detect other leptons in order to have a complete monitored neutrino beam.
ENUBET studies all technical and physics challenges to demonstrate the feasibility of a monitored neutrino beam:[9] it has built a full-scale demonstrator of the instrumented decay tunnel (3 m length and partial azimuthal coverage) and assesses costs and physics reach of the proposed facility.
The first end-to-end simulation of the ENUBET monitored neutrino beam was published in 2023.