Status of the HOLMES Experiment to Directly Measure the Neutrino Mass

TL;DR

The HOLMES experiment aims to directly measure the neutrino mass using calorimetric detection of electron capture decay of $^{163}$Ho, addressing systematic uncertainties and leveraging recent detector advancements.

Contribution

This paper presents the current status, technical challenges, and future perspectives of the HOLMES experiment for neutrino mass measurement.

Findings

Design of a large array of low temperature microcalorimeters with $^{163}$Ho implantation.

Potential to provide a model-independent measurement of neutrino mass.

Progress in detector technology enabling precise calorimetric measurements.

Abstract

The assessment of neutrino absolute mass scale is still a crucial challenge in today particle physics and cosmology. Beta or electron capture spectrum end-point study is currently the only experimental method which can provide a model independent measurement of the absolute scale of neutrino mass. HOLMES is an experiment funded by the European Research Council to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the electron capture decay of the artificial isotope $^{163}$Ho. In a calorimetric measurement the energy released in the decay process is entirely contained into the detector, except for the fraction taken away by the neutrino. This approach eliminates both the issues related to the use of an external source and the systematic uncertainties arising from decays on excited final states. The most suitable detectors for this type of measurement are low temperature thermal detectors, where all the energy released into an absorber is converted into a temperature increase that can be measured by a sensitive thermometer directly coupled with the absorber. This measurement was originally proposed in 1982 by A. De Rujula and M. Lusignoli, but only in the last decade the technological progress in detectors development has allowed to design a sensitive experiment. HOLMES plans to deploy a large array of low temperature microcalorimeters with implanted $^{163}$Ho nuclei. In this contribution we outline the HOLMES project with its physics reach and technical challenges, along with its status and perspectives.