Erlangen 2026 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 26: Instrumentation V

HK 26.7: Talk

Wednesday, March 18, 2026, 15:15–15:30, PHIL A 301

Studies of Cosmogenic Backgrounds in a Shielded Crystal Calorimeter for DarkMESA — •Shumit Mitra — Institute for Nuclear Physics, Johannes Gutenberg University Mainz, Germany

DarkMESA is a planned electron beam-dump experiment at the MESA accelerator facility in Mainz, designed to search for light dark matter particles mediated by a hypothetical dark photon γ′ using a compact crystal calorimeter. Due to the extremely low expected interaction rates of beyond-the-Standard-Model processes, efficient background suppression is essential. DarkMESA therefore relies on a combination of passive and active shielding to mitigate cosmogenic and beam-related backgrounds. This contribution presents the development and characterization of a prototype calorimeter composed of 5 × 5 PbWO₄ crystals of dimensions 2 × 2 × 20 cm³ with single-sided SiPM readout per crystal. The calorimeter is hermetically surrounded by inner and outer plastic scintillator veto layers and passive lead shielding. The detector performance with respect to cosmogenic muon- and gamma-induced backgrounds in the relevant energy range around 5 MeV and above is discussed and compared to detailed simulations. First results from long-term background measurements with the full detector setup are presented. Possible contributions from cosmogenic neutrons are briefly addressed. Finally, an outlook on the implications of these studies for a PbWO₄-based DarkMESA detector is given.

Keywords: DarkMESA; Light Dark Matter; BSM; Calorimeter; SiPM