M. Böhles | Searcharxiv

arXiv2026

Performance of a first multi-cell WOM-based liquid scintillator detector as prototype for the SHiP Surrounding Background Tagger

The Search for Hidden Particles (SHiP) Experiment was approved by CERN in 2024. Feebly-interacting particles that are produced in a proton Beam Dump Facility (BDF) will decay in the 50m-long Decay Volume of the experiment, which needs to be enveloped by a hermetic veto detector: The Surrounding Background Tagger (SBT). Its technology relies on liquid scintillator, composed of linear alkylbenzene and 2,5-diphenyloxazole, as active detector material and Wavelength-shifting Optical Module (WOM) tubes collecting the primary scintillation photons. The liquid scintillator volume is segmented in large cells of typically 120cm x 80cm x 20cm that are equipped with two WOMs each. Here, we report on the performance of a full-scale 2x2-cell prototype detector which was exposed to 5GeV muons at the CERN PS T9 test beam facility to study the detector response and its time and spatial resolution for minimum ionising particles crossing multiple detector cells.

physics.ins-det↗

arXiv2024

Performance of a First Full-Size WOM-Based Liquid Scintillator Detector Cell as Prototype for the SHiP Surrounding Background Tagger

As a prototype detector for the SHiP Surrounding Background Tagger (SBT), we constructed a cell (120 cm x 80 cm x 25 cm) made from corten steel that is filled with liquid scintillator (LS) composed of linear alkylbenzene (LAB) and 2,5-diphenyloxazole (PPO). The detector is equipped with two Wavelength-shifting Optical Modules (WOMs) for light collection of the primary scintillation photons. Each WOM consists of an acrylic tube that is dip-coated with a wavelength-shifting layer on its surface. Via internal total reflection, the secondary photons emitted by the molecules of the wavelength shifter are guided to a ring-shaped array of 40 silicon photomultipliers (SiPMs) coupled to the WOM for light detection. The granularity of these SiPM arrays provides an innovative method to gain spatial information on the particle crossing point. Several improvements in the detector design significantly increased the light yield with respect to earlier proof-of-principle detectors. We report on the performance of this prototype detector during an exposure to high-energy positrons at the DESY II test beam facility by measuring the collected integrated yield and the signal time-of-arrival in each of the SiPM arrays. The resulting detection efficiency and reconstructed energy deposition of the incident positrons are presented, as well as the spatial and time resolution of the detector. These results are then compared to Monte Carlo simulations.

physics.ins-det↗