Performance of segmented lead glass absorber calorimeter prototype

Abstract

Sampling calorimeter is essential for physics measurements in high-energy frontier collider experiments using particle-flow-algorithm (PFA) . Three-dimensional information is used to separate the particles in a jet incident on the calorimeter. Therefore, in calorimeters optimized for PFA, both energy information and position information data are essential. Location information can be improve by creating a very finely granulated detection layer, however, the energy resolution is principally determined by the sampling ratio. Energy resolution can be dramatically improved if energy information can read using lead glass as the absorption layer. To independently observe energy in the narrow area required to use the PFA, it is necessary to divide the lead glass into small pieces that are independent of each other. A small optical sensor is required to read out the Cherenkov light from a small lead-glass block. To read maany small lead-glass blocks, the dead volume between layers can be reduced by using MPPC, and by keeping the optical sensor thickness small. This sampling calorimeter using lead-glass blocks as its absorption layers is useful for experiments that requiring the high-energy resolution in the future. We are developing a calorimeter prototype with a segmented-lead-glass absorption layer that takes the PFA into account. The prototype absorber layer's size is 9 × 9 × 4 cm3 and consists of nine 3 × 3 × 4 cm3 lead-glass blocks. The detection layer can read position information with a 1 × 1 cm2 resolution using a plastic scintillator with a width of 1 cm. Backward energy leakage is measured with a tail catcher using a single 12 × 12 × 25 cm3 lead-glass block. All detectors are optically readout using MPPCs. We tested this prototype using the positron beam at Research Center for ELectron PHoton Science, Tohoku University. First, a positron beam was injected into each lead-glass block channel for calibration. Then, the full prototype's performance was evaluated by injecting the beam. As a result of the beam-injection test of the prototype with three segmented lead-glass absorption layers, the overall energy resolution was found to be 13%. We will report upon the performance of this prototype.