Search for magnetic monopoles with the ANTARES underwater neutrino telescope

摘要

The ANTARES underwater neutrino telescope, located in the Mediterranean Sea at a depth of 2475 m, 40kmoff the Provencal coast, is composed by an array of 885 photomultipliers distributed on 12 vertical lines. The detectoris fully operational since May 2008. Besides the detection of neutrino-induced muons, the telescope is more generallysensitive to particles which emit Cherenkov light, and, thanks to its large volume, offers new opportunities to improve thesensitivity to exotic particles, such as magnetic monopoles. Magnetic monopoles are stable magnetically charged particlesfirst introduced in quantum mechanics by Dirac in 1931, which showed that their existence would give an explanation tothe quantization of the electric charge. They would have been produced in the Early Universe, and would bring a firstproof to the existence of grand unified models. The paper introduces magnetic monopoles and their signal caracteristicsin a neutrino telescope, and then describes the analysis which uses a dedicated algorithm able to reconstruct the velocityof the incoming particles. A new upper limit on the upward going magnetic monopole flux, extracted from ANTARESdata taken in 2008, is presented. It is, at present, the best worldwide constraint in the velocity range = [0.625, 1], andprovides, for the first time with a neutrino telescope, a constraint for monopole velocities below the Cherenkov threshold.