Electric charge reconstruction with rich detector of the AMS experiment

The Alpha Magnetic Spectrometer (AMS) to be installed on the International Space Station (ISS), in 2005, will be equipped with a proximity focusing Ring Imaging Cerenkov detector. This detector, will be equipped with an aerogel radiator, a lateral conical mirror and a detection plane made of around 700 photomultipliers and light-guides, enabling measurements of particle electric charge and velocity. When a charged particle traverses a dielectric medium with speed greater than the velocity of light in that medium, emission of Cerenkov photuns occurs, their number being proportional to the particle's charge squared. Therefore, different charged nuclei can be discriminated with basis on their Cerenkov signals. In order to determine the number of emitted photons, attenuation factors such as scattering and absorption in the radiator, the mirror reflectivity, the geometrical acceptance, the light guide efficiency and photomultiplier's (PMT) quantum efficiency have to be evaluated. The method presented, has its foundations on the estimation of the overall event efficiency, which takes all the attenuation factors into account. Some of these factors have a wide range of variation and an event-by-event based charged reconstruction method is required.