The neutrino is one of the most fascinating particles in the Standard Model of particle physics. Despite important discoveries over the last ten years, a number of questions remain unanswered: How heavy is a neutrino? Is the neutrino its own antiparticle? Does the well-known left-handed neutrino have a right-handed partner? Investigating these unknown neutrino properties is the key to gaining a better understanding of the composition and evolution of the universe, and is the ultimate goal of the KATRIN/TRISTAN Research Group.
The Karlsruhe Tritium Neutrino experiment (KATRIN) is a large-scale experiment that is currently being commissioned at Karlsruhe Institute of Technology (KIT) whose aim is the direct determination of the neutrino mass. An international research collaboration comprising around 150 members from 17 institutes in six different countries is involved in this experiment.
The KATRIN experiment comprises an ultrahigh-intensity source of heavy hydrogen (tritium) and a high-precision spectrometer. One electron and one neutrino are emitted during the radioactive decay of the tritium atoms in the source. The energy released in this decay is randomly divided between the two particles. However, the electron can never possess all of the decay energy, as the neutrino lays claim to at least the energy that corresponds to its mass (E = mc2).
By determining the maximum energy of the electron, it is then possible to derive the mass of the neutrino. The KATRIN spectrometer is used to measure the energy of the electron produced when the tritium decays. KATRIN started operations in June 2018, and aims to determine the neutrino mass with a sensitivity of 200 millielectronvolts over the next few years. Our Research Group will concentrate on the upcoming data analysis and on developing a novel detector system for KATRIN, known as TRISTAN.
Owing to its excellent source and spectrometer properties, the KATRIN experiment enables us to not only determine the neutrino mass, but also to search for a new variant of the particle: The right-handed partner of the neutrino, the so-called sterile neutrino.
The existence of sterile neutrinos has been predicted in numerous theories, but has thus far not been confirmed experimentally. Sterile neutrinos in the mass range of a few kiloelectronvolts are suitable candidates for dark matter. In order to search for dark matter, KATRIN has to be equipped with a new detector and read-out system: TRISTAN (Tritium Beta Decay to Search for Sterile Neutrinos).
Our Group is heading the development of this novel silicon multi-pixel detector system. This work is being undertaken together with the Halbleiterlabor (HLL) of the Max Planck Society, Politecnico di Milano, Bicocca di Milano, Lawrence Berkeley National Laboratory, Oak Ridge National Laboratory, CEA Saclay, and the Karlsruhe Institute of Technology.
In July 2016, the French COCOTE (Compact Compton Telescope) project was already using a prototype of the silicon detector, which was launched into the stratosphere attached to a balloon.
Commissioning of the vacuum system of the KATRIN Main Spectrometer
Journal of Instrumentation, Volume 11, April 2016
A White Paper on keV Sterile Neutrino Dark Matter
M. Drewes, T. Lasserre, A. Merle, S. Mertens
submitted to Journal of Cosmology and Astroparticle Physics (JCAP) (2016)
Sensitivity of Next-Generation Tritium Beta-Decay Experiments for keV-Scale Sterile Neutrinos
S. Mertens, T. Lasserre, S. Groh, G. Drexlin, F. Glück, A. Huber, A. W. P. Poon, M. Steidl, N. Steinbrink, C. Weinheimer
Journal of Cosmology and Astroparticle Physics (JCAP) 1502 (2015) 02, 020
Wavelet approach to search for sterile neutrinos in tritium beta- decay spectra
S. Mertens, K. Dolde, M. Korzeczek, F. Glück, S. Groh, R. D. Martin, A. W. P. Poon, M. Steidl
Physical Review D 91 (2015) 4, 042005
Current Direct Neutrino Mass Experiments
G. Drexlin, V. Hannen, S. Mertens, C. Weinheimer
Advances in High Energy Physics, Volume 2013 (2013)