Neutrino research Since late August 2006,
CERN has directed a
beam of
muon neutrinos from the
CERN SPS accelerator to the Gran Sasso lab, 730 km away, where they are detected by the
OPERA and
ICARUS detectors, in a study of
neutrino oscillations that will improve on the results of the
Fermilab to
MINOS experiment. In May 2010,
Lucia Votano, Director of the Gran Sasso laboratories, announced, "The OPERA experiment has reached its first goal: the detection of a
tau neutrino obtained from the transformation of a
muon neutrino, which occurred during the journey from Geneva to the Gran Sasso Laboratory." This was the first observed tau neutrino candidate event in a muon neutrino beam, providing further evidence that neutrinos have mass. (Research first determined that neutrinos have mass in 1998 at the Super-Kamiokande neutrino detector.) Neutrinos must have mass for this transformation to occur; this is a deviation from the classic
Standard Model of
particle physics, which assumed that neutrinos are massless. An effort to determine the
Majorana/Dirac nature of the neutrino, called
CUORE (Cryogenic Underground Observatory for Rare Events), is operating in the laboratory (as of 2018). The detector is shielded with lead recovered from an ancient Roman shipwreck, due to the ancient lead's lower radioactivity than recently minted lead. The artifacts were given to CUORE from the
National Archaeological Museum in
Cagliari. In September 2011, Dario Autiero, a researcher of Institute of Nuclear Physics in
Lyon, France, presented preliminary findings that indicated neutrinos produced at CERN were arriving at OPERA detector about 60 ns earlier than they would if they were travelling at the speed of light. This
faster-than-light neutrino anomaly was not immediately explained. The results were subsequently investigated and confirmed to be wrong. They were caused by a flawed optic fiber cable in
OPERA receiver of the laboratory, resulting in late arrival of the clock signal to which the neutrinos' arrivals were compared. Although the official statement published by OPERA does not declare any anomaly in the velocity of the neutrinos, and therefore the case is completely solved, the development of the story has given the community pause for thought. In 2014
Borexino measured directly, for the first time, the neutrinos from the primary
proton-proton fusion process in the Sun. This result is published on Nature. This measurement is consistent with the expectations derived from the standard solar model of
J. Bahcall along with the theory of solar neutrino oscillations as described by
MSW theory. In 2020
Borexino measured also solar neutrinos originated from
CNO cycle, a fusion process common in giant stars but uncommon in the Sun (only 1% of Sun's energy output). With this outcome
Borexino has unraveled both the two processes powering the Sun and many main sequence stars.
Experiments ==See also==