Speaker
Description
For the High-Luminosity LHC Run 5, the LHCb experiment aims to operate at an instantaneous luminosity of up to 1.0×10$^{34}$ cm$^{−2}$s$^{-1}$, requiring a complete overhaul of the electromagnetic calorimeter (ECAL) known as PicoCal. To mitigate extreme pile-up and combinatorial background, the PicoCal upgrade will introduce O(10) picosecond timing capabilities and significantly increased transverse granularity across the detector. The innermost regions, expected to face radiation doses up to 1 MGy, will be equipped with Spaghetti Calorimeter (SpaCal) technology, combining dense absorbers (Tungsten and Lead) with innovative fast organic and inorganic scintillators. The outer regions will utilize the Shashlik technology, upgraded with fast wavelength-shifting (WLS) fibres. Several Photomultiplier Tube (PMT) candidates are under investigation, and extensive laboratory tests have been performed to ensure they meet the Run 5 requirements, in particular in terms of timing resolution. Recent test beam campaigns have successfully evaluated SpaCal modules equipped with the new accelerated inorganic GAGG crystal fibres, demonstrating energy and time resolutions that are fully in line with the detector's performance requirements and in line with simulations. At the same time, the first prototype of the SPIDER ASIC was successfully evaluated in test beam, demonstrating a time resolution that is compatible with the performance achieved using standard DAQ digitizers. This presentation will detail the PicoCal upgrade strategy, summarize recent R&D achievements on fast scintillating materials, PMTs, and ASICs, and discuss the latest performance results from test beam measurements.