Development of proton beam irradiation system for the NA65/DsTau experiment

Tau neutrino is the least studied lepton of the Standard Model (SM). The NA65/DsTau experiment targets to investigate D-s, the parent particle of the nu(tau), using the nuclear emulsion-based detector and to decrease the systematic uncertainty of nu(tau) flux prediction from over 50% to 10% for future beam dump experiments. In the experiment, the emulsion detectors are exposed to the CERN SPS 400 GeV proton beam. To provide optimal conditions for the reconstruction of interactions, the protons are required to be uniformly distributed over the detector's surface with an average density of 10(5) cm(-2) and the fluctuation of less than 10%. To address this issue, we developed a new proton irradiation system called the target mover. The new target mover provided irradiation with a proton density of 1.01 x 10(5) cm(-2) and the density fluctuation of 1.9 +/- 0.3% in the DsTau 2021 run.

Automated summary

The NA65/DsTau experiment aims to study the least studied lepton of the Standard Model, the tau neutrino. By using a nuclear emulsion-based detector exposed to CERN's proton beam, the experiment reduces the systematic uncertainty of tau neutrino flux prediction. A new proton irradiation system called the target mover has been developed to provide irradiation with optimal proton density and density fluctuation.