The upgrade of the Belle II forward calorimeter

The new facility SuperKEKB will be an upgrade of the existing KEKB electron–positron asymmetric collider, with a target luminosity of 8 × 10 35 cm − 2 s − 1 , about 40 times greater than that of KEKB. The detector will also be upgraded to cope with the higher luminosity, pile-up and occupancy. We report here on the design and development of the new pure CsI calorimeter for the forward region. An intensive R&D is being carried on to study the performance of pure CsI crystals with Avalanche Photodiodes readout. Results about the relative energy resolution of this detector, along with radiation hardness studies of all the components, are presented. A matrix of 16 crystals has been put on an electron beam at the BTF facility in Frascati and results in terms of energy resolution of this prototype are also discussed.