Takaaki Kajita and Arthur B. McDonald are recognised for their key contributions to the experiments which demonstrated that neutrinos change identities. This metamorphosis requires that neutrinos have mass. The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe.

Swedish physicists in prominent roles in search of neutrinos

Physicists from Stockholm University and Uppsala University have prominent roles in the work at IceCube, an international project with over 250 physicists from various countries.

IceCube Lab på isen. Foto: Dag Larsen, IceCube/NSF
IceCube Lab above the ice. Photo: Dag Larsen, IceCube/NSF

IceCube is a particle detector at the South Pole that records the interactions of the nearly massless sub-atomic particle called the neutrino. A total of 5160 light sensors (optical modules) have been embedded in the three-kilometer deep glacier, to observe the light that is generated by particles passing through the ice as a result of neutrino interactions.

En DOM-modul sänks ner i ett ishål. Foto: Jim Haugen, IceCube/NSF.
A DOM module is lowered down into an ice hole. Photo: Jim Haugen, IceCube/NSF.

They take up a volume of one cubic kilometer (which is why it’s called IceCube). In addition to that, there are 162 ice-filled tanks on the surface, used to detect showers of cosmic rays which react in the atmosphere. In each tank, there are two optical modules. Over 1000 of the modules in IceCube were built in Stockholm.

Looking for deviations in neutrinos patterns

IceCube is mainly meant for observing neutrinos coming from space from as yet unidentified sources. These neutrinos also undergo oscillations.
“Our research shows that the neutrinos that reach the Earth have oscillated on their journey through space in a similar way as predicted by the experiments that are today honored with the Nobel Prize. Now we continue to look for deviations in these patterns. If we find them, it may mean that we have to look at the physics in this area in a new way”, says Chad Finley, who also has hopes for new results when IceCube is upgraded to include the PINGU detector, which aims to study neutrino oscillations more closely.

The meaning for cosmology

At the Department of Physics, PhD student Jessica Elevant conducts research on the theoretical side of neutrino oscillations. Neutrino masses and oscillations are also important for understanding the universe at large, i.e. in cosmology. If neutrinos and antineutrinos oscillate differently they could play a role for generating the antimatter to matter asymmetry we observe in the universe. Neutrinos also contribute to dark matter, and they affect how large-scale structures in the universe develop.  

Read more about the research at IceCube

Press release from The Royal Swedish Academy of Sciences