The calorimetric spectrum of the electron-capture decay of $^{163}$Ho. A preliminary analysis of the preliminary data

TL;DR

This paper discusses the calorimetric spectrum of $^{163}$Ho electron-capture decay, analyzing preliminary data to understand the spectral features and the role of two-hole states, electron shakeoff, and shakeup in neutrino mass measurements.

Contribution

It provides a preliminary analysis of calorimetric data for $^{163}$Ho decay, highlighting the importance of two-hole states and electron shakeoff effects in spectral modeling.

Findings

Two-hole states significantly affect the spectrum.

Good agreement between theory and preliminary data.

Electron shakeoff must be included in models.

Abstract

It is in principle possible to measure directly the electron neutrino mass (or masses and mixing angles) in weak electron-capture decays. The optimal nuclide in this respect is $^{163}$Ho. The favoured experimental technique, currently pursued in various experiments (ECHo, HOLMES and NuMECS) is "calorimetric". The calorimetric energy spectrum is a sum over the unstable vacant orbitals, or "holes", left by the electrons weakly captured by the nucleus. We discuss the current progress in this field and analize the preliminary data. Our conclusion is that, as pointed out by Robertson, the contribution of two-hole states is not negligible. But --in strong contradistinction with the tacit conclusion of previous comparisons of theory and observations-- we find a quite satisfactory agreement. A crucial point is that, in the creation of secondary holes, electron shakeoff and not only electron shakeup must be taken into account.