Development of the GRAiNITA prototype with ZnWO4 and BGO crystal grains

We will present the development of two medium-size prototypes of GRAiNITA, a next-generation shashlik calorimeter, based on the use of ZnWO4 and BGO crystal grains, respectively, soaked in a high-density and high-refractive index liquid. As in the LiquidO detection technique[1], due to the presence of the grains, the scintillation light remains stochastically confined in the area of production; for this reason, it can be collected and transferred towards the photodetectors by the use of wavelength shifting fibers evenly distributed in the detection volume, similarly as in a conventional shashlik calorimeter.GRAiNITA represents a very appealing electromagnetic calorimeter candidate for high energy physics experiments for future electron-positron colliders. Indeed, due to the extreme fine sampling, GRAiNITA has the potential to reach a photon energy resolution of R~2%/sqrt(E) [2], thus increasing the precision of flavor physics with rare decays to photons or neutral pions. In this communication, we will present the outcomes of the study that led us to the choice of the best suited fibers for ZnWO4 and BGO, respectively, and we will present the effect observed on the light propagation, when adding isopropanol in the detection volume (as a first approximation of future liquids), to fill the space between the crystal grains. Finally, we will discuss the development and characterization of the prototypes, presenting either the mechanical and the electronic design.