Tagged Neutrino Beams

This contribution describes a new experimental method for accelerator based neutrino experiments, called neutrino tagging. This technique consists in instrumenting a beam line with silicon trackers. Using these trackers, each neutrino originating from a π±→μ±ν decay can be reconstructed based on simple kinematic relations. This reconstruction allows to precisely determine the energy, direction, initial flavour and chirality of each beam neutrino. As a result, the initial neutrino flux is precisely determined. Moreover, based on time and angular coincidence, the tagged neutrinos can be individually associated to the neutrinos interacting in the neutrino detector and used for physics analyses. In this contribution, a detailed description of the technique is presented, as well as a discussion on its advantages. The potential of the method at long base line experiments is discussed and quantified using the Protvino to KM3NeT/ORCA setup as a case study. Finally, the perspectives and early results on a demonstration of the neutrino tagging technique using the existing NA62 experiment are shown.