Seminario INFN di Fenomenologia delle Particelle Elementari

Direct determination of the electron neutrino and anti-neutrino mass can be obtained by the analysis of electron capture and beta spectra respectively. In the last years, experiments analyzing the 3H beta spectrum reached a limit on the electron antineutrino mass of 2 eV. The upper limit on the electron neutrino mass m(ve) is still two orders of magnitudes higher, at 225 eV. The Electron Capture in 163Ho experiment, ECHo, is designed to investigate m(ve) in the sub-eV region and reach the same sensitivity as foreseen for electron antineutrino mass in new 3H-based experiments.

In ECHo, high sensitivity on a finite m(ve)  will be reached by the analysis of the endpoint region in high statistics and high resolution calorimetrically measured 163Ho spectra. To perform this experiment, high purity 163Ho source will be enclosed in a large number of low temperature metallic magnetic micro-calorimeters which are readout using the microwave multiplexing technique. This approach allows for a very good energy resolution, below ΛEWHM < 5 eV and for a fast time resolution well below 1 μs.

Thanks to the modular approach, the ECHo experiment is designed to be stepwise up-graded. The first on-going phase, ECHo-1k, is characterized by a 163Ho activity of about 1 kBq enclosed in about 100 pixels. The statistics of 1010 events in the 163Ho spectrum will allow for improving the limit on m(ve) by more than one order of magnitude.

In this talk, the present status of the ECHo-1k experiment will be discussed as well as the plans for the next phases.