Low-Energy Calibration of SuperCDMS HVeV Cryogenic Silicon Calorimeters Using Compton Steps

TL;DR

This paper demonstrates a novel calibration method for cryogenic silicon calorimeters using Compton steps at 0 V bias, revealing a weaker detector response than expected, which impacts low-mass dark matter detection accuracy.

Contribution

It introduces the use of Compton steps for sub-keV calibration of SuperCDMS HVeV detectors at 0 V bias, providing a new calibration approach and insights into detector response modeling.

Findings

Calibration at 0 V bias is feasible using Compton steps.

Detector response at 0 V is about 30% weaker than expected.

Comparison with high-voltage calibration highlights modeling challenges.

Abstract

Cryogenic calorimeters for low-mass dark matter searches have achieved sub-eV energy resolutions, driving advances in both low-energy calibration techniques and our understanding of detector physics. The energy deposition spectrum of gamma rays scattering off target materials exhibits step-like features, known as Compton steps, near the binding energies of atomic electrons. We demonstrate a successful use of Compton steps for sub-keV calibration of cryogenic silicon calorimeters, utilizing four SuperCDMS High-Voltage eV-resolution (HVeV) detectors operated with 0 V bias across the crystal. This new calibration at 0 V is compared with the established high-voltage calibration using optical photons. The comparison indicates that the detector response at 0 V is about 30% weaker than expected, highlighting challenges in detector response modeling for low-mass dark matter searches.