Massive Neutrinos

Neutrino oscillation experiments have clearly proven that neutrinos mix and have non-zero masses. They provide differences between squared neutrino mass eigenvalues but not the absolute mass values. Cosmology, neutrinoless double beta decay searches and direct neutrino mass investigations with single beta decay and electron capture provide already stringent limits on the neutrino masses. The neutrino oscillation results require at least one of the 3 neutrino masses to weigh 50 meV or more. Already now the course should be set in order to be able to determine such a neutrino mass scale directly or indirectly with the next or next but one generation of experiments. In addition we should be open and sensitive for the unexpected, e.g. sterile neutrinos.

With which experimental method this can work and what effort is necessary is not yet really clear.

• Firstly, the advances in cryogenic microbolometers and the CRES technology of Project 8 will open new experimental doors to improve the sensitivity in direct neutrino mass search beyond KATRIN, which also possesses upgrade options.
• Secondly, promising progress is repeatedly being made in underground reduction in the search for neutrinoless double beta decay. But a huge gain in sensitivity is required considering that the normal mass hierarchy is favoured in global neutrino oscillation fits with about 2 sigma.

The aim of the workshop is to discuss with national and international experts from experiments as well as from theory in the intensive atmosphere of a WE Heraeus Seminar at the ``Physikzentrum which paths are most promising for determining the neutrino mass scale in the laboratory, or whether this ambitious goal must be reserved only for cosmology. Of course there will be room for related and neighbouring topics as well.

The conference language will be English. The Wilhelm and Else Heraeus-Foundation bears the cost of full-board accommodation for all participants.