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تسجيل مستخدم جديدStatus of the HOLMES Experiment to Directly Measure the Neutrino Mass
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The assessment of neutrino absolute mass scale is still a crucial challenge in today particle physics and cosmology. Beta or electron capture spectrum end-point study is currently the only experimental method which can provide a model independent measurement of the absolute scale of neutrino mass. HOLMES is an experiment funded by the European Research Council to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the electron capture decay of the artificial isotope $^{163}$Ho. In a calorimetric measurement the energy released in the decay process is entirely contained into the detector, except for the fraction taken away by the neutrino. This approach eliminates both the issues related to the use of an external source and the systematic uncertainties arising from decays on excited final states. The most suitable detectors for this type of measurement are low temperature thermal detectors, where all the energy released into an absorber is converted into a temperature increase that can be measured by a sensitive thermometer directly coupled with the absorber. This measurement was originally proposed in 1982 by A. De Rujula and M. Lusignoli, but only in the last decade the technological progress in detectors development has allowed to design a sensitive experiment. HOLMES plans to deploy a large array of low temperature microcalorimeters with implanted $^{163}$Ho nuclei. In this contribution we outline the HOLMES project with its physics reach and technical challenges, along with its status and perspectives.
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The European Research Council has recently funded HOLMES, a new experiment to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the decay of 163Ho. The calorimetric measurement eliminates sys
tematic uncertainties arising from the use of external beta sources, as in experiments with beta spectrometers. This measurement was proposed in 1982 by A. De Rujula and M. Lusignoli, but only recently the detector technological progress allowed to design a sensitive experiment. HOLMES will deploy a large array of low temperature microcalorimeters with implanted 163Ho nuclei. The resulting mass sensitivity will be as low as 0.4 eV. HOLMES will be an important step forward in the direct neutrino mass measurement with a calorimetric approach as an alternative to spectrometry. It will also establish the potential of this approach to extend the sensitivity down to 0.1 eV. We outline here the project with its technical challenges and perspectives.
HOLMES is a new experiment aiming at directly measuring the neutrino mass with a sensitivity below 2 eV. HOLMES will perform a calorimetric measurement of the energy released in the decay of $^{163}$Ho. The calorimetric measurement eliminates systema
tic uncertainties arising from the use of external beta sources, as in experiments with spectrometers. This measurement was proposed in 1982 by A. De Rujula and M. Lusignoli, but only recently the detector technological progress has allowed to design a sensitive experiment. HOLMES will deploy a large array of low temperature microcalorimeters with implanted $^{163}$Ho nuclei. HOLMES, besides being an important step forward in the direct neutrino mass measurement with a calorimetric approach, will also establish the potential of this approach to extend the sensitivity down to 0.1 eV and lower. In its final configuration HOLMES will collect about $3cdot 10^{13}$ decays with 1000 detectors characterized by an instrumental energy resolution of the order of few eV and a time resolution of few microseconds. To embed the $^{163}$Ho into the gold absorbers a custom mass separator ion implanter is being developed. The detectors used for the HOLMES experiment will be Mo/Cu bilayers TESs (Transition Edge Sensors) on SiN$_x$ membrane with gold absorbers. Microwave multiplexed rf-SQUIDs are the best available technique to read out large array of such detectors. An extensive R&D activity is in progress in order to maximize the multiplexing factor while preserving the performances of the individual detectors. The current activities are focused on the the single detector performances optimization and on the $^{163}$Ho isotope production and embedding. A preliminary measurement of a sub-array of $4times 16$ detectors is planned late in 2017. In this contribution we present the HOLMES project with its technical challenges, its status and perspectives.
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