Abstract
Two photo-neutron sources, Y88Be9 and Sb124Be9, have been used to investigate the ionization yield of nuclear recoils in the CDMSlite germanium detectors by the SuperCDMS collaboration. This work evaluates the yield for nuclear recoil energies between 1 and 7 keV at a temperature of ∼50 mK. We use a geant4 simulation to model the neutron spectrum assuming a charge yield model that is a generalization of the standard Lindhard model and consists of two energy dependent parameters. We perform a likelihood analysis using the simulated neutron spectrum, modeled background, and experimental data to obtain the best fit values of the yield model. The ionization yield between recoil energies of 1 and 7 keV is shown to be significantly lower than predicted by the standard Lindhard model for germanium. There is a general lack of agreement among different experiments using a variety of techniques studying the low energy range of the nuclear recoil yield, which is most critical for interpretation of direct dark matter searches. This suggests complexity in the physical process that many direct detection experiments use to model their primary signal detection mechanism and highlights the need for further studies to clarify underlying systematic effects that have not been well understood up to this point.
| Original language | English (US) |
|---|---|
| Article number | 122002 |
| Journal | Physical Review D |
| Volume | 105 |
| Issue number | 12 |
| DOIs | |
| State | Published - Jun 15 2022 |
Bibliographical note
Funding Information:The SuperCDMS Collaboration gratefully acknowledges technical assistance from the staff of the Soudan Underground Laboratory and the Minnesota Department of Natural Resources. The CDMSlite and iZIP detectors were fabricated in the Stanford Nanofabrication Facility, which is a member of the National Nanofabrication Infrastructure Network, sponsored and supported by the NSF. Funding and support were received from the National Science Foundation, the U.S. Department of Energy (DOE), Fermilab URA Visiting Scholar Grant No. 15-S-33, NSERC Canada, the Canada First Excellence Research Fund, the Arthur B. McDonald Institute (Canada), the Department of Atomic Energy Government of India (DAE), the Department of Science and Technology (DST, India) and the DFG (Germany)—Project No. 420484612 and under Germany’s Excellence Strategy—EXC 2121 “Quantum Universe”—390833306. Femilab is operated by Fermi Research Alliance, LLC, SLAC is operated by Stanford University, and the PNNL is operated by the Battelle Memorial Institute, each for the U.S. Department of Energy under Contracts No. DE-AC02-37407CH11359, No. DE-AC02-76SF00515, and No. DE-AC05-76RL01830, respectively.
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© 2022 American Physical Society.