Emulsion chamber with big radiation length for detecting neutrino oscillations

A conceptual scheme of a hybrid-emulsion spectrometer for investigating various channels of neutrino oscillations is proposed. The design emphasizes detection of tau leptons by detached vertices, reliable identification of electrons, and good spectrometry for all charged particles and photons. A distributed target is formed by layers of low-Z material, emulsion-plastic-emulsion sheets, and air gaps in which tau decays are detected. The tracks of charged secondaries, including electrons, are momentum-analyzed by curvature in magnetic field using hits in successive thin layers of emulsion. The tau leptons are efficiently detected in all major decay channels, including tau(-) --> e(-)nu<(nu)over bar>. The performance of a model spectrometer, that contains 3 t of nuclear emulsion and 20 t of passive material, is estimated for different experimental environments. When irradiated by the nu(mu) beam of a proton accelerator over a medium baseline of [L/E-nu] similar to 1 km/GeV, the spectrometer will efficiently detect either the nu(mu) --> nu(tau) or the nu(mu) --> nu(e) transitions in the mass-difference region of Delta m(2) similar to 1 eV(2), as suggested by the results of LSND. When exposed to the neutrino beam of a muon storage ring over a long baseline of [L/E-nu] similar to 10-20 km/GeV, the model detector will efficiently probe the entire pattern of neutrino oscillations in the region Delta m(2) similar to 10(-2)-10(-3) eV(2), as suggested by the data on atmospheric neutrinos. (C) 2000 Elsevier Science B.V. All rights reserved.