Study of tau neutrino production at the CERN SPS

At the CERN SPS, the DsTau project has been proposed to study tau-neutrino production aiming at providing important information for future ντ measurements. Precise measurement of the ντ cross section would enable a search for new physics effects in ντ charged current interactions. It also has practical implications for neutrino oscillation experiments. The dominant source of ντ is the sequential decay of Ds mesons produced by proton interactions, whose uncertainty dominates current uncertainty in the ντ cross section measurement. The project aims at reducing the systematic uncertainty from about 50% to 10% by measuring the Ds differential production cross section. For this purpose, emulsion detectors with a nanometre-precision readout will be used to detect small kinks of the Ds → τ decay. An emulsion detector has a position resolution of 50 nm, allowing for the detection of Ds → τ → X double kinks in a few millimeter range.