Design of an enhanced 1 GeV electron neutrino beam

Abstract

An enhanced ν e beam would be useful for experiments that have been proposed to investigate the time evolution of a ν e beam or to test the universality of ν e and ν μ interactions. We have performed detailed calculations to maximize the flux of electron neutrinos through a detector while minimizing the more copious muon neutrinos produced at 30 GeV proton accelerators. The ν e beam is formed from the semi-leptonic decay modes of the neutral kaon. Muon neutrinos generated by decays of charged pions and kaons are suppressed by a dipole sweeping magnet. The ν e/ ν μ ratio is enhanced from its usual value of ∼ 1 1000 to a value of ∼ 1 2 , albeit at a low flux. We find with this design a typical flux of 1.5 × 10 7 ν e/m 2 s. We find that a high magnetic field (≥ 40 kG) is essential to achieve this ν e/ ν μ enhancement. Although the use of collimators and/or plugs inside the magnet reduces the ν μ flux, the ν e flux is also diminished so that there is little beneficial effect on the ν e/ ν μ ratio. Magnetic focusing horns and quadrupole beams do not enhance the ν e/ ν μ ratio. The accuracy of the energy dependence of the calculation, as well as the absolute normalization of the fluxes, is determined by a subsidiary calculation of the ν μ yield from the magnetic horn focused beam at Brookhaven National Laboratory. This calculation is the first to our knowledge to agree well with the ν μ yield as measured in the BNL seven foot bubble chamber.