Observation of a low energy nuclear recoil peak in the neutron calibration data of an Al2O3 crystal in CRESST-III

G Angloher and F Casadei and E Cipelli and L Canonica and F Dominsky and D Hauff and A Langenkämper and M Mancuso and B Mauri and C Moore and F Petricca and F Pröbst and K Schäffner and M Stahlberg and L Stodolsky and M Zanirato and A Bento and S Di Lorenzo and D Fuchs and PV Guillaumon and V Zema and J Burkhart and S Fichtinger and VM Ghete and H Kluck and V Mokina and S Banik and L Einfalt and F Reindl and J Schieck and C Schwertner and D Valdenaire and A Bertolini and L Burmeister and E Fascione and P Murali and B von Krosigk and R Breier and M Jeskovsky and P Povinec and C Bucci and P Gorla and M Olmi and F Pucci and C Pagliarone and L Pattavina and J Dohm and J Jochum and C Strandhagen and I Usherov and FV Feilitzsch and M Kaznacheeva and T Ortmann and W Potzel and J Rothe and S Schönert and R Strauss and A Erb and H Kraus and M Macko and V Palusovà, PHYSICAL REVIEW D, 112, 102008 (2025).

DOI: 10.1103/bb31-pgzg

The current generation of cryogenic solid state detectors used in direct dark matter and CE nu NS searches typically reach energy thresholds of O(10) eV for nuclear recoils. For a reliable calibration in this energy regime a method has been proposed, providing monoenergetic nuclear recoils at low energies similar to 100 eV-1 keV. In this work we report on the observation of a peak at (1113.6(-6.5)(+6.5)) eV in the data of an Al2O3 crystal in CRESST-III, which was irradiated with neutrons from an AmBe calibration source. We attribute this monoenergetic peak to the radiative capture of thermal neutrons on Al-27 and the subsequent deexcitation via single. emission. We compare the measured resultswith the outcome of Geant4 simulations and investigate the possibility to make use of this effect for the energy calibration of Al-2 O-3 detectors at lowenergies. We further investigate the possibility of a shift in the expected energy scale of this effect caused by the creation of defects in the target crystal.

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