Time Analysis of Cherenkov Emission in Quartz Fiber Calorimeters

Quartz fiber calorimeters emerge as a promising solution at high-energy colliders due to their exceptional radiation resistance, alleviating the need for cumbersome response monitoring, frequent recalibration, or costly replacements of active components. They also emerge as a detector of choice for accurate timing measurements because of the prompt emission of Cherenkov light. By utilizing fast waveform digitization of the signals from silicon photomultipliers (SiPMs), we are also able to differentiate between events with few photons. In our feasibility studies, we also found that by analyzing the time structure of Cherenkov radiation in quartz fibers, it is possible to reconstruct a 3D image of the particle shower, making highly granular quartz fiber calorimeters appropriate for energy reconstruction using machine learning and artificial intelligence techniques. We experimentally studied the Cherenkov light signals coming from quartz fibers by detecting them with SiPMs using a 3 GeV positron beam at CERN (The European Laboratory for Particle Physics in Geneva, Switzerland) in July 2023. With SiPMs featuring a fast output with signal pulse widths as narrow as 1.5 ns, we were able to distinguish peaks arriving 1 ns apart. With the speed of light in quartz being roughly 2/3 c, this results in a space resolution of ~20 cm for the detection of the particle. With advanced analysis techniques, we aim for improved spatial resolution, an equivalent of 250 ps or better.