Estudi de l'oscil·lació de neutrins en l'experiment K2K

This project proposes the participation of two Spanish groups in the K2K experiment, designed to confirm the existence of neutrino oscillations, currently considered the most likely explanation of the deficit observed in the atmospheric neutrino data by the Super Kamiokande experiment. The fact that there is no observed deficit of electronic neutrinos suggests that the dominant oscillation is with a mass split and maximal mixing angle. K2K sends a beam, produced in the KeK laboratory, located in Tsukuba, near Tokyo, to the Super Kamiokande detector (SK hereafter), in the Kamioka mine, about 250 km away. The mean energy of the neutrinos is about 1 GeV, thus, one expects a strong distortion of the neutrino beam observed in SK with respect to that observed in the near detector, located at the source. The observation of such distortion will be the final confirmation of the oscillation hypothesis and will allow an additional measurement of the oscillation parameters. In order to perform this measurement, it is necessary to extrapolate the spectrum measured in the near detector to SK. This requires a very detailed knowledge of the neutrino beam composition, since both detectors intercept different angular regions of the beam, due to the different distance. In turn, the knowledge of the neutrino beam composition requires a precise understanding of the production cross sections of the hadrons whose decay originate the neutrino beam (pions and kaons). The HARP experiment, recently completed at CERN, has included on its program a data sample of collisions of protons of 12 GeV (the energy of the KEP PS) with an aluminium target, exact replica of the K2K target. The K2K collaboration, has manifested strong interest in new groups capable of analysing this data and porting the knowledge of the corresponding cross sections to the K2K analysis chain (&)