Probing the absolute neutrino mass scale with the 163Ho: the HOLMES project

M De Gerone ,D R Schmidt ,M Faverzani ,A Giachero ,G Gallucci ,Johnathon D Gard ,Daniel S Swetz ,Daniel Becker ,F Gatti ,S Nisi ,D Schumann ,Joseph W Fowler ,M Biasotti ,Bradley K Alpert ,A Orlando ,E Ferri ,G C Hilton ,S Heinitz ,C D Reintsema ,G Pessina ,J A B Mates ,A Puiu ,M Ribeiro-Gomes ,U Köester ,M Lusignoli ,S Ragazzi ,R Dressier,J P Hays-Wehle ,Joel N Ullom ,V Ceriale ,Douglas A Bennett ,Leila R Vale

doi:10.1088/1742-6596/1342/1/012092

Abstract

The HOLMES project aims to directly measure the electron neutrino mass using the electron capture decay (EC) of 163Ho down to the eV scale. It will perform a precise measurement of the end-point of the 163Ho calorimetric energy spectrum to search for the deformation caused by a finite electron neutrino mass. The choice of 163Ho as source is driven by the very low Q-value of the EC reaction (around 2.8 keV), which allows for a high sensitivity while keeping the overall activities to reasonable value (O(102)Hz/detector), thus reducing the pile-up probability. A large array made of thousands of Transition Edge Sensor based micro-calorimeters will be used for a calorimetric measurement of the EC 163Ho spectrum. The calorimetric approach, with the source embedded inside the detector, eliminates systematic uncertainties arising from the use of an external beta-source, and minimizes the effect of the atomic de-excitation process uncertainties. The commissioning of the first implanted sub-array is scheduled for the end of 2017. It will provide useful data about the EC decay of 163Ho together with a first limit on neutrino mass. In this paper the current status of the main tasks will be summarized: the TES array design and engineering, the isotope preparation and embedding, and the development of a high speed multiplexed SQUID read-out system for the data acquisition.

Highlights

The neutrino mass direct measurement takes advantage of proper nuclear processes, usually exploiting the kinematics of beta decays characterized by low Q-values
Based on the same approach, the KATRIN [2] experiment is expected to reach the sensitivity of 0.2 eV in few years
From the spectrometric one, the calorimetric approach has the advantage to avoid systematic effects coming from possible energy losses in the source or decays to excited states, being the source embedded in the detector

Summary

International Conference on Topics in Astroparticle and Underground Physics

M De Gerone, B Alpert, D Becker, D Bennett, M Biasotti, V Ceriale, R Dressler, M Faverzani, E Ferri, J Fowler, G Gallucci, J Gard, F Gatti, A Giachero, J Hays-Wehle, S Heinitz, G Hilton, U Koester, M Lusignoli, J Mates, S Nisi, A Orlando, G Pessina, A Puiu, S Ragazzi, C Reintsema, M Ribeiro-Gomes, D Schmidt, D Schumann, D Swetz, J Ullom and L Vale

Introduction

The HOLMES project