Neutrinos

Neutrinos are some of the most abundant particles of the universe, but relatively little is known about them.

The department has a long history in studying their properties. In the past we used the Soudan2 experiment, which was originally designed to search for the decay of protons, to measure the flux of atmospheric neutrinos. It was observed that not as many muon neutrinos were detected as anticipated, indicating that some of them transformed into another particle. The department is currently involved in several experiments trying to unlock the secret of the neutrino.

The T2K and MINOS experiment are both situated in a beam of muon neutrinos and measure, how the neutrinos spontaneously transform themselves into electron or tau neutrinos. This process is called neutrino oscillations and would not be possible in the standard model of particle physics, where neutrinos are massless. Having observed this effect, we now know that neutrinos have mass and that the mass and flavour eigenstates are distinct. Measuring this transitions more precisely may help us to understand why there is more matter than anti-matter in the universe. To this end, we are involved in a number of future initiatives (MINOS+, LBNE, Laguna-LBNO), who try to build the next generation of experiments in Europa, the USA or Japan.

SNO experiment (based in Sudbury, Canada) was the major milestone in neutrino physics. It was designed to not only measure the total number of electron neutrinos that are generated by nuclear fusion in the sun, but also to detect whether any of these have changed into different neutrinos types before arriving at the Earth. It unambiguously demonstrated that a large fraction of neutrinos coming from the Sun did, indeed, transform into different neutrino "flavours," thereby resolving a long standing mystery in neutrino physics and opening an important new avenue of research. The SNO experiment has now finished taking data, but the basic experimental apparatus is going to be used in the new SNO+ experiment. This project will have a rich experimental programme that will not only extend the measurements of solar neutrinos, but also study neutrinos produced in the Earth, nuclear reactors and possibly supernovae as well as hunting for rare processes such as neutrinoless double beta decay.