Evidence grows for neutrino mutation


Physicists announced further proof Wednesday that mysterious particles called neutrinos that seem to go “missing” during the journey from the sun to Earth are in fact changing form along the way and arriving undetected.

The evidence is a muon-type neutrino that was emitted by CERN’s research laboratory near Geneva and arrived as a tau neutrino at the INFN Gran Sasso Laboratory in Italy, 730 km away, they said in a statement.

It is only the third time that the mutation has been observed by the OPERA experiment, an international project launched in 2001 specifically to detect the bizarre change. “Its observation confirms something scientists have been studying for more than 40 years: the fact that neutrinos induced by cosmic rays impinging on the Earth atmosphere arrive far fewer than expected,” the statement said.

A Nobel-winning 1969 hypothesis shed light on the mystery by suggesting the subatomic particles were changing type.

There are three types, or flavors, of neutrino, an electrically neutral subatomic particle that rarely interacts with matter. Under the prevailing Standard Model of physics, neutrinos cannot have mass, but the outcome of the experiment suggests they in fact do.

In the OPERA experiment, a beam of neutrinos produced at CERN is fired at the Gran Sasso, an underground laboratory that houses a 4,000-ton neutrino detector. The detector scans the arriving particles for tau neutrinos, knowing that only muon neutrinos were fired by CERN. Finding a tau neutrino proves that an “oscillation,” or change, happened along the way.

OPERA detected its first tau neutrino in 2010 and the second in 2012. The search for tau neutrinos will continue for another two years, the statement said.