FOR2202: ECHo

The DFG Research Unit "Neutrino Mass Determination by Electron Capture in ¹⁶³Ho - ECHo" aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following the electron capture process of ¹⁶³Ho. In the ECHo experiment, arrays of low temperature metallic magnetic calorimeters with high energy resolution and fast response time, having the ¹⁶³Ho source embedded in the absorber, will be used to calorimetrically measure the EC spectrum.  Independent measurements of the Q_EC-value will be performed using high precision Penning trap. For the Q_EC measurements as well as for the calorimetric measurement of the ¹⁶³Ho spectrum, high purity ¹⁶³Ho sources will be produced. Detailed studies of the background and of methods to reduce it will be performed in order to increase the sensitivity of the calorimetric measurement.

We aim to achieve the required experimental conditions and the knowledge to be able to investigate the electron neutrino mass in the sub-eV range. In particular, within the scope of this Research Unit, we will carry out a medium-size experiment (Echo-1k) with the aim of investigating the value of the electron neutrino mass in the range below 10 eV by means of high precision and high statistics calorimetric measurement of the ¹⁶³Ho EC spectrum. The expected  result will improve the limit on the electron neutrino mass by more than one order of magnitude, since presently the most stringent limit is m(v_e) < 225 eV (95% CL).