Expected performance of the ALPIDE pixel layers in ALICE FoCal

Abstract: The ALICE experiment is designed to study ultra-relativistic heavy-ion collisions at the Large Hadron Collider (LHC). As part of its major upgrades for Run 4, the Forward Calorimeter (FoCal) will be installed during Long Shutdown 3 (LS3). FoCal enables precise measurements of direct photon production at forward rapidity, providing a sensitive probe of the gluon distribution in protons and nuclei. This paper introduces the expected performance of the forward electromagnetic calorimeter (FoCal-E) and presents several potential strategies for mitigating occupancy and BUSY violation challenges in the pixel layers of FoCal-E. Beam test results demonstrate that back biasing effectively reduces pixel occupancy. Meanwhile, SystemC simulations explore additional mitigation strategies-such as grid masking and a regional trigger-to further minimize BUSY violations and enhance detector performance under high-luminosity conditions.