Mesure du moment électrique dipolaire du neutron – nEDM

Measurements of the neutron Electric Dipole Moment (nEDM), as well as EDM of other particles or atoms, are considered to be of top priority by the particle physics community, since they may reveal new sources of CP violation and give first evidence of physics beyond the Standard Model (SM). The discovery of such new sources would also be of particular interest for cosmology being one of the necessary conditions proposed by Sakharov to explain the baryonic asymmetry (matter-antimatter asymmetry) observed in the Universe. New EDM measurements will come at the right time to compare with the results expected from the Large Hadron Collider regarding the search for Super Symmetric signatures and new CP violation mechanisms in B mesons decay (LHC-B) or searches for forbidden flavour changing processes like mu-->e gamma. These are the main reasons motivating this project which aims at an improved measurement of the neutron EDM by two orders of magnitude. To reach this goal, an optimized spectrometer will be constructed and installed at the new UCN (Ultra Cold Neutron, i.e. neutron having energy ' 200 neV) source under construction at the Paul Sherrer Institut (PSI, Suisse). This project is supported by an international collaboration of fourteen laboratories, including the two partners (LPC Caen and LPSC Grenoble) involved in this application. In view of the construction of this large apparatus, tasks have been defined and shared among the collaborative institutions. The present funding request aims at financing a large fraction of the activities taken in charge by the two French laboratories. This project has been reviewed three times since 2002 by the IN2P3 Scientific Council, the most recent one in July 2007. The Council stressed the importance of the scientific case "Le CS est convaincu du grand intérêt de mesures de précision telles que la recherche d'un moment électrique dipolaire du neutron" and expressed then its support to the chosen strategy.