100
R. N. Mohapatra
Fig. 13.3 SNO heavy water detector. Source: Wikipedia.org
established that the neutrinos from the Sun oscillate and then undergo both
neutral and charged current weak interactions, confirming the three-neutrino
picture of solar neutrino oscillations. The SNO experiment established that
neutrinos from the Sun were not disappearing into something unknown, but
rather simply changing their identity from ν e to ν μ and ν τ due to neutrino
oscillations. The leaders of both the Japanese and Canadian teams, Takaaki
Kajita and Arthur Mcdonald (Fig. 13.4), respectively, were awarded the Nobel
Prize in 2015 for their confirmation of the solar neutrino deficit discovery and
the confirmation that the solar neutrinos oscillate to ν μ and ν τ . These series
of experiments are of fundamental importance for unraveling the mysteries of
the forces and matter in the universe, as we will see below.
13.6 Atmospheric Neutrino Oscillation
Just like the Sun, the Earth’s atmosphere is also a copious source of neutrinos—
both muon and electron types. The way they originate is as follows. There are
high-energy protons in the cosmic rays, which come from extra-solar sources