The Italian Almanac

neutrino detector

Flip Flopping Neutrinos

Italian researchers have observed the third shape-shifting' neutrino ever seen, spreading fresh light on these enigmatic sub-atomic particles. The observation, like the previous two, was made in the Gran Sasso laboratory of Italy's National Nuclear Physics Institute (INFN), deep under the largest mountain in Italy outside the Alps.

The INFN researchers in the OPERA (Oscillation Project with Emulsion-tRacking Apparatus) project again saw one type of neutrino changing into another kind as it zipped in from the CERN European nuclear research centre in the Alps near Geneva. This type of spontaneous "flip-flopping" had never been seen before May 2010 when the Gran Sasso lab announced the first instance in what was hailed as potentially the most exciting find in particle physics in decades. Scientists say further observations of this behaviour may shed light on how matter came to dominate over antimatter in the universe, and what happens to missing neutrinos.

For 40 years scientists have been wondering why many fewer neutrinos arrive from the Sun and other stars than models predict. The most likely hypothesis is that they have not in fact gone astray but have simply changed form. The OPERA experiment was set up five years ago to verify the theory.

OPERA International Director Giovanni De Lellis said finding the third transformed neutrino was "an important confirmation of the previous two observations. "This event has characteristics which make it unmistakable compared to other processes," he stressed. The so-called 'oscillation' could lead to a radical rethink in particle physics. The third transformation of a muon neutrino into a tau neutrino during the 730km, 2.4 millisecond trip from the CERN lab, "makes us confident, from a statistical standpoint, that we will be able to confirm the oscillation," De Lellis said.

The CERN Neutrino To Gran Sasso (CNGS) experiment was expressly set up to establish that neutrinos can change 'flavour' - an hypothesis first raised almost 70 years ago by famed Italian physicist Guido Pontecorvo. If neutrinos really are oscillating, this could go a long way to explaining why the mass of the visible universe only adds up to a fraction of the total mass value derived from the observed dynamics in galaxies.

Physicists have long been wondering where the majority of the mass in the universe could be. If neutrinos oscillate then theory dictates that they must have mass. It is probably only a very tiny mass, but there are so many neutrinos around in the universe - almost a billion times as many as there are protons - that they could account for at least as much mass as exists in visible stars.