Low-energy nuclear recoils (NRs) are hard to measure, because they produce few e-/h+ pairs in solids - i.e., they have low "ionization yield."A silicon detector was exposed to thermal neutrons over 2.5 live days, probing NRs down to 450 eV. The observation of a neutron capture-induced component of NRs at low energies is supported by the much-improved fit upon inclusion of a capture NR model. This result shows that thermal neutron calibration of very low recoil energy NRs is promising for dark matter searches, coherent neutrino experiments, and improving understanding of ionization dynamics in solids.
Bibliographical noteFunding Information:
The authors thank the SuperCDMS Collaboration for the use of the detector and readout electronics. This work was supported by Department of Energy Grants No. DE-SC0012294 and No. DE-SC0021364 and Grant No. NSF-1743790 via the Partnerships for International Research and Education programs (PIRE). We also acknowledge the support of the Germanium Materials and Detectors Advancement Research Consortium (GEMADARC).
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