13 Neutrinos Oscillate and Hence They Weigh
99
establishing the broad theoretical picture of the supernova as a consequence of
stellar collapse. It also put major constraints on new ideas of physics beyond
the standard model. For example, it put limits on the magnetic moment of the
neutrino, the new interactions of the neutrino, properties of new hypothetical
particles called the axion, as well as many others.
The light energy collected by photo-multiplier tubes in the SuperKamiokande experiment would signal the arrival of the solar or atmospheric
neutrino. The experiment started taking data in 1996. The results for the
oscillation of atmospheric neutrino were announced in the bi-annual world
Neutrino meeting in Takayama, Japan (Neutrino’98), to an eager audience,
which was captivated by the announcement. The 1998 announcement
consisted of 2 years of observation. The author of this book was in the audience
when this happened. The atmosphere was electric and simply unbelievable.
There were announcements in the press by political leaders from all over the
world glorifying this result. President Clinton said after this discovery in an
MIT commencement speech, “Just yesterday in Japan, physicists announced
a discovery that tiny neutrinos have mass. Now, that may not mean much to
most Americans, but it may change our most fundamental theories from the
nature of the smallest sub-atomic particles to how the universe itself works,
and indeed how it expands.” The Super-Kamiokande experiment was a 100
million dollar experiment by Japanese-American collaboration and made the
observations that led to the monumental discovery. It transformed the field
of physics. The neutrino, which since its birth was thought to have no mass,
was now proven to have mass. This was evident that the Nobel Prize–winning
Standard model had a flaw in it and it had to be amended. That was big!
The Super-Kamiokande experiment was followed by a Canadian experiment in Sudbury mines, known as the SNO experiment (Fig. 13.3), which used
1000 tons of heavy water for solar neutrino detection. The SNO experiment
was set up 6800 feet underground in the INCO’s Creighton mine near
Sudbury, Canada. Neutrinos from the Sun reacted with the heavy water to
produce both electrons due to charged current interactions caused by the
exchange of W boson, and neutrinos due to neutral current interactions caused
by the exchange of Z bosons. In the neutral current process, the heavy water
nucleus deuterium breaks up to a proton and neutron. The neutral current
detection by solar neutrinos was a completely new contribution of the SNO
experiment. The neutron from the neutral current reaction then wanders
around until it gets captured in the heavy water, and when it does, it emits
a photon, which is observed by the Cherenkov detectors. Thus, the SNO
experiment observed both charged and neutral current processes, whereas the
Super-Kamiokande observed only the charged current reaction. They together
99
establishing the broad theoretical picture of the supernova as a consequence of
stellar collapse. It also put major constraints on new ideas of physics beyond
the standard model. For example, it put limits on the magnetic moment of the
neutrino, the new interactions of the neutrino, properties of new hypothetical
particles called the axion, as well as many others.
The light energy collected by photo-multiplier tubes in the SuperKamiokande experiment would signal the arrival of the solar or atmospheric
neutrino. The experiment started taking data in 1996. The results for the
oscillation of atmospheric neutrino were announced in the bi-annual world
Neutrino meeting in Takayama, Japan (Neutrino’98), to an eager audience,
which was captivated by the announcement. The 1998 announcement
consisted of 2 years of observation. The author of this book was in the audience
when this happened. The atmosphere was electric and simply unbelievable.
There were announcements in the press by political leaders from all over the
world glorifying this result. President Clinton said after this discovery in an
MIT commencement speech, “Just yesterday in Japan, physicists announced
a discovery that tiny neutrinos have mass. Now, that may not mean much to
most Americans, but it may change our most fundamental theories from the
nature of the smallest sub-atomic particles to how the universe itself works,
and indeed how it expands.” The Super-Kamiokande experiment was a 100
million dollar experiment by Japanese-American collaboration and made the
observations that led to the monumental discovery. It transformed the field
of physics. The neutrino, which since its birth was thought to have no mass,
was now proven to have mass. This was evident that the Nobel Prize–winning
Standard model had a flaw in it and it had to be amended. That was big!
The Super-Kamiokande experiment was followed by a Canadian experiment in Sudbury mines, known as the SNO experiment (Fig. 13.3), which used
1000 tons of heavy water for solar neutrino detection. The SNO experiment
was set up 6800 feet underground in the INCO’s Creighton mine near
Sudbury, Canada. Neutrinos from the Sun reacted with the heavy water to
produce both electrons due to charged current interactions caused by the
exchange of W boson, and neutrinos due to neutral current interactions caused
by the exchange of Z bosons. In the neutral current process, the heavy water
nucleus deuterium breaks up to a proton and neutron. The neutral current
detection by solar neutrinos was a completely new contribution of the SNO
experiment. The neutron from the neutral current reaction then wanders
around until it gets captured in the heavy water, and when it does, it emits
a photon, which is observed by the Cherenkov detectors. Thus, the SNO
experiment observed both charged and neutral current processes, whereas the
Super-Kamiokande observed only the charged current reaction. They together