# High-sensitivity Kinetic Inductance Detectors for CALDER

## TL;DR

This paper discusses the development of high-sensitivity cryogenic light detectors using Kinetic Inductance Detectors (KIDs) for background discrimination in neutrinoless double-beta decay experiments, achieving resolutions below 20 eV RMS.

## Contribution

It introduces improved KID-based cryogenic light detectors with enhanced energy resolution, demonstrating progress from prototype arrays to single KID designs.

## Key findings

- Baseline resolution of 154 eV RMS with initial array prototype.
- Improved design achieved 82 eV RMS resolution with a single KID.
- Potential for background suppression in rare event searches.

## Abstract

Providing a background discrimination tool is crucial for enhancing the sensitivity of next-generation experiments searching for neutrinoless double- beta decay. The development of high-sensitivity (< 20 eV RMS) cryogenic light detectors allows simultaneous read-out of the light and heat signals and enables background suppression through particle identification. The Cryogenic wide- Area Light Detector with Excellent Resolution (CALDER) R&D already proved the potential of this technique using the phonon-mediated Kinetic Inductance Detectors (KIDs) approach. The first array prototype with 4 Aluminum KIDs on a 2 $\times$ 2 cm2 Silicon substrate showed a baseline resolution of 154 $\pm$ 7 eV RMS. Improving the design and the readout of the resonator, the next CALDER prototype featured an energy resolution of 82 $\pm$ 4 eV, by sampling the same substrate with a single Aluminum KID.