Kathrin Valerius - Probing the neutrino mass: latest results from the KATRIN experiment

 

What is the mass of a neutrino?

This apparently simple question has remained unanswered since the neutrino was introduced into the subatomic particle zoo more than 90 years ago. The absolute neutrino mass scale has important implications from elementary particle physics to astrophysics and cosmology. Therefore, it is at the focus of numerous contemporary research activities.

 

The currently most sensitive direct (that is, largely model-independent) approach to "weigh" the neutrino uses the kinematics of weak decays, notably tritium beta-decay, to search for the tiny imprint of the neutrino mass in the tail of the beta spectrum. The Karlsruhe Tritium Neutrino experiment (KATRIN) combines an ultra-luminous gaseous tritium source and a high-resolution electrostatic filter with magnetic adiabatic collimation to perform a precision measurement of the tritium beta-spectrum. 

 

Based on its first science runs taken in 2019, KATRIN has already shaved off more than a factor of 2 from the mass range allowed by previous experiments. The measurement yields a new upper limit on the neutrino mass of 0.8 eV/c^2 at 90% C.L. [1]. The projected target sensitivity of KATRIN after five years of data-taking is 0.2 eV/c^2. In the talk, I will introduce the working principle of the experiment [2] and the analysis methods [3]. Apart from presenting the latest results, I will also give an outlook on physics "beyond the neutrino mass“ which can be probed with KATRIN.

 

[1] First direct neutrino-mass measurement with sub-eV sensitivity, 

M. Aker et al. (KATRIN Coll.), arXiv:2105.08533, in press

[2] The design, construction, and commissioning of the KATRIN experiment, 

M. Aker et al. (KATRIN Coll.), Journal of Instrumentation 16 (2021) T08015

[3] Analysis methods for the first KATRIN neutrino-mass measurement,

M. Aker et al. (KATRIN Coll.), Phys. Rev. D 104 (2021) 012005