# 17th International Conference on Topics in Astroparticle and Underground Physics (TAUP 2021)

26 August 2021 to 3 September 2021

## HOLMES: progresses towards a calorimetric neutrino mass measurement with eV scale mass sensitivity

27 Aug 2021, 14:05
10m
Talk in parallel session Neutrino physics and astrophysics

### Speaker

Angelo Nucciotti (Dipartimento di Fisica, Università di Milano-Bicocca, Milano, Italy)

### Description

The assessment of the absolute neutrino mass scale is still a crucial challenge in today’s particle physics and cosmology. Beta or electron capture decay spectra end-point measurements are currently the only experimental methods which can provide a model-independent measurement of the absolute neutrino mass scale.
While KATRIN is successfully pushing the mass sensitivity below 1 eV, there is a strong need for radically different direct experiments to confirm and strengthen present and future KATRIN's results. $^{163}$Ho electron capture calorimetric experiments are among the best candidates for this task. In calorimetric measurements, the energy released in the decay process is entirely contained into the detector, except for the fraction carried away by the neutrino: this provides an independent direct measurement that has completely different systematic uncertainties. The most suitable detectors for this type of measurement are low-temperature thermal detectors, where all the energy released in an absorber is converted into a temperature increase that can be measured by a sensitive thermometer directly coupled with the absorber. HOLMES will deploy a large array of low temperature microcalorimeters with ion-implanted $^{163}$Ho nuclei.
The ultimate goal of HOLMES is a statistical neutrino mass sensitivity of 1 eV to be achieved with an array of 1000 pixels, each with a $^{163}$Ho ion-implanted activity of about 300 Bq. As a near-term goal, HOLMES is preparing to ion-implant a lower dose to give an activity of a few Bequerels per pixel. A measurement with such an array is planned to begin by 2021 and will provide a sensitivity of less than 10 eV.
In this contribution we outline the HOLMES project with its physics reach and technical challenges, along with its status and prospects. In particular, we will present the status of HOLMES activities aiming at the production of the first low-dose ion-implanted TES array and at the first neutrino mass measurement campaign. We will also discuss the prospects and strategies for a future $^{163}$Ho experiment with a sub-eV neutrino mass sensitivity.