Low Energy Backgrounds and Excess Noise in a Two-Channel Low-Threshold Calorimeter

Abstract

We describe observations of low energy excess (LEE) events, background events observed in all light dark matter direct detection calorimeters, and noise in a Transition Edge Sensor based two-channel silicon athermal phonon detector with 375 meV baseline energy resolution. We measure two distinct LEE populations: ``shared'' multichannel events with a pulse shape consistent with substrate athermal phonon events, and sub-eV events that couple nearly exclusively to a single channel with a significantly faster pulse shape. These ``singles'' are consistent with events occurring within the aluminum athermal phonon collection fins. Similarly, our measured detector noise is higher than the theoretical expectation. Measured noise can be split into an uncorrelated component, consistent with shot noise from small energy depositions within the athermal phonon sensor itself, and a correlated component, consistent with shot noise from energy depositions within the silicon substrate's phonon system.

12 pages, 12 figures

References in corpus (9)

• EXCESS workshop: Descriptions of rising low-energy spectra
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• Results on sub-GeV Dark Matter from a 10 eV Threshold CRESST-III Silicon Detector
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Cited by in corpus (9)

• First Limits on Light Dark Matter Interactions in a Low Threshold Two Channel Athermal Phonon Detector from the TESSERACT Collaboration
• Low-Energy Backgrounds in Solid-State Phonon and Charge Detectors
• A Transition Edge Sensor Operated in Coincidence with a High Sensitivity Athermal Phonon Sensor for Photon Coupled Rare Event Searches
• Low-Energy Calibration of SuperCDMS HVeV Cryogenic Silicon Calorimeters Using Compton Steps
• Spontaneous generation of athermal phonon bursts within bulk silicon causing excess noise, low energy background events and quasiparticle poisoning in superconducting sensors
• Enhanced Athermal Phonon Responsivity in a Kinetic Inductance Detector with Integrated Phonon Collectors
• Novel coincidence detection technique for precision measurement of neutron-capture-induced nuclear recoils
• Performance of a SuperCDMS HVeV Detector with Sub-eV Energy Resolution and Single Charge-sensitivity
• Prospect of the NUCLEUS Experiment at Chooz for Coherent Elastic Neutrino-Nucleus Scattering and New Physics Searches