The calorimetric spectrum of the electron-capture decay of ${}^{163}$Ho. The spectral endpoint region

Abstract

The electron-neutrino mass (or masses and mixing angles) may be directly measurable in weak electron-capture decays. The favoured experimental technique is "calorimetric". The optimal nuclide is ${}^{163}$Ho, and several experiments (ECHo, HOLMES and NuMECS) are currently studying its decay. The most relevant range of the calorimetric-energy spectrum extends for the last few hundred eV below its endpoint. It has not yet been well measured. We explore the theory, mainly in the cited range, of electron capture in ${}^{163}$Ho decay. A so far neglected process turns out to be most relevant: electron-capture accompanied by the shake-off of a second electron. Our two main conclusions are very encouraging: the counting rate close to the endpoint may be more than an order of magnitude larger than previously expected; the "pile-up" problem may be significantly reduced.

Clarifying changes suggested by a referee. Results unchanged. 14 pages, 15 figures

References in corpus (4)

• HOLMES - The Electron Capture Decay of 163Ho to Measure the Electron Neutrino Mass with sub-eV sensitivity
• Direct Measurement of the Mass Difference of Ho163 and Dy163 Solves the Q-Value Puzzle for the Neutrino Mass Determination
• The Electron Capture ${}^{163}$Ho Experiment ECHo: an overview
• Electron Capture in 163Ho and Overlap plus Exchange Corrections and the Neutrino Mass

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