The LHCb PicoCal

Abstract The goal of the LHCb Upgrade II is to operate at an instantaneous luminosity of about 1.0 × 10 34 cm -2 s -1 in order to collect a dataset of 300 fb -1 . The substantial upgrades required for the LHCb electromagnetic calorimeter (ECAL) during Long Shutdown 4 of the LHC, driven by the high radiation doses in the central region and the increased particle densities, are collectively referred to as PicoCal . Several scintillating sampling ECAL technologies are currently under investigation in an ongoing R&D campaign in view of PicoCal : the Spaghetti Calorimeter (SpaCal) with garnet scintillating crystals and tungsten absorber, SpaCal with scintillating plastic fibres and lead absorber, and Shashlik modules based on polystyrene tiles, lead absorber, and fast wavelength-shifting fibres. Timing capabilities with a resolution of a few tens of picoseconds for electromagnetic showers and increased granularity with denser absorbers in the central region are essential for pile-up mitigation. Test-beam measurements of prototype SpaCal modules have demonstrated time resolutions better than 20 ps at high energies. The current LHCb Shashlik modules already exhibit good timing performance. This proceeding summarises the proposed new features and the state-of-the-art of the R&D project, and reports the latest results from the test-beam campaigns.