A prototype large-angle photon veto detector for the P326 experiment at CERN

Understand

The P326 experiment at the CERN SPS has been proposed with the purpose of measuring the branching ratio for the decay K^+ \to \pi^+ \nu \bar{\nu} to within 10%.

• The photon veto system must provide a rejection factor of 10^8 for \pi^0 decays.
• We have explored two designs for the large-angle veto detectors, one based on scintillating tiles and the other using scintillating fibers.
• We have constructed a prototype module based on the fiber solution and evaluated its performance using low-energy electron beams from the Frascati Beam-Test Facility.