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

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2019-08, Vol.936, p.252-253
• Main Authors: De Gerone, M., Alpert, B., Becker, D., Bennett, D., Biasotti, M., Ceriale, V., Dressler, R., Faverzani, M., Ferri, E., Fowler, J., Gallucci, G., Gard, J., Gatti, F., Giachero, A., Hays-Wehle, J., Heinitz, S., Hilton, G., Koester, U., Lusignoli, M., Mates, J., Nucciotti, A., Nisi, S., Orlando, A., Pessina, G., Puiu, A., Ragazzi, S., Reintsema, C., Ribeiro Gomes, M., Schmidt, D., Schumann, D., Swetz, D., Ullom, J., Vale, L.
• Format: Article
• Language: English
• Subjects: Electron capture; Holmium; Neutrino mass measurement; Transition edge sensors
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/j.nima.2018.10.108

The HOLMES project aims to directly measure the ν mass down to the eV scale using the electron capture decay (EC) of 163Ho. It will perform a precise calorimetric measurement of the end-point of the Ho energy spectrum looking for the deformation caused by a finite ν mass. The choice of 163Ho as source is driven by the very low Q-value of the EC reaction, which allows for high sensitivity with low activities (O(102)Bq/detector), thus reducing the pile-up probability. A large array made by thousands of transition edge sensors based micro-calorimeters will be used. The calorimetric approach eliminates systematic uncertainties arising from the use of an external β source, and minimizes the effect of the atomic de-excitation process. The commissioning of the first implanted sub-array is scheduled for the end of 2018. It will provide useful data about the EC decay of 163Ho together with a first limit on ν mass.