Speaker
Description
L. Thulliez(1) for the CRAB collaboration
(1) IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
The detection of the coherent elastic neutrino-nucleus scattering (CEνNS) at reactors or of hypothetical light dark matter (DM) particles will allow to test new physics beyond the standard model. In both cases their direct detection will lead to sub-keV nuclear recoils. This requires low energy thresholds of few 10 eV along with energy resolutions of few eV, which are currently achieved by cryogenic detector operated at mK temperatures. Understanding the response of these detectors at a sub-keV energy scale is therefore crucial but remains a challenge. Recently the CRAB collaboration has proposed [1] to calibrate the cryo-detectors with pure nuclear recoils induced by thermal neutron radiative captures, perfectly mimicking the CEνNS or DM signals.
We will discuss the first measurement performed with a CaWO4 cryogenic detector of the NUCLEUS experiment [3] exposed to a low flux of thermal neutrons produced by a commercial 252Cf source. The measured recoil spectrum shows a nuclear recoil peak at around 112 eV (182W(n,γ)183W) with a 3σ significance and evidence at the 6σ level of the nuclear recoil spectrum, in very good agreement with FIFRELIN-GEANT4 simulations [4]. This talk will emphasis the software developments that have been performed leading to such a good agreement. These mainly concern the modeling of the 252Cf source with FIFRELIN, the neutron slowing-down in GEANT4 that has been recently improved [5] and the accurate computation of the nuclear recoil induced by thermal neutron capture thanks to FIFRELIN.
Then we will present the interplay between the timing of nuclear de-excitations and atom recoils in matter, which has recently been investigated in coupling the FIFRELIN and IRADINA (binary collision approximation) codes. We will discuss how these timing effects can significantly impact the spectrum of nuclear recoils, especially for germanium and silicone detectors [7], and so the calibration. The simulation results for the main crystal materials used in CEνNS and DM communities, that are available online [8] along with a Geant4 interface [9], will be presented.
A series of high precision measurements is in preparation at the TRIGA Mark-II reactor in Vienna where the gammas escaping the cryo-detector will be tagged in addition to the nuclear recoil. This will allow to get more calibration peaks to test the linearity of the detector response, the quenching factors and also to set constraints on nuclear models and solid state physics.
[1] L. Thulliez, D. Lhuillier et al., Calibration of nuclear recoils at the 100 eV scale using neutron capture, JINST, 16, 7 (2021)
[2] O. Litaize, O. Serot, and L. Berge. Fission modelling with FIFRELIN. Eur. Phys. J. A, 51(12):177 2015.
[3] R. Strauss et al., Gram-scale cryogenic calorimeters for rare-event searches, Phys. Rev. D 96, 022009 (2017)
[4] CRAB collaboration, NUCLEUS collaboration, H. Abele et al., Observation of a nuclear recoil peak at the 100 eV scale induced by neutron capture, Phys. Rev. Lett. 130, 211802 (2023) arXiv:2211.03631 [nucl-ex] (2022)
[5] L. Thulliez, C. Jouanne, E. Dumonteil, Improvement of Geant4 Neutron-HP package: From methodology to evaluated nuclear data library, Nuclear Inst. and Methods in Physics Research, A 1027 (2022) 166187
[6] C. Borschel and C. Ronning. Ion beam irradiation of nanostructures – A 3D Monte Carlo simulation code. Nucl. Instrum. Meth. Phys. Res. B: Beam Interactions with Materials and Atoms, 269(19):2133–2138, 2011
[7] CRAB collaboration, G. Soum-Sidikov et al., Study of collision and γ-cascade times following neutron-capture processes in cryogenic detectors, Phys. Rev. D 108, 072009 (2023) arXiv:2305.10139 [physics.ins-det] (2023)
[8] G. Soum-Sidikov, L. Thulliez, O. Litaize, A. Chalil, J.-P. Crocombette, and D. Lhuillier, Fifradina dataset for radiative thermal neutron-capture processes in cryogenic detectors (CRAB), 10.5281/zenodo.7936552, 2023.
[9] L. Thulliez, H. Kluck et A. Bonhomme, Fifrelin4Geant4, (2023) DOI:10.5281/zenodo.7933381 , http://gitlab.com/lthullie/fifrelin4geant4
