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R. N. Mohapatra
There are two ways to detect neutrino oscillation: one way is as described
above, where one looks for depletion of the original intensity of the beam, and
a second way where one looks for the appearance of the new kind of neutrino
which the original beam turned partially into. Each neutrino produces its
partner lepton in a weak force mediated scattering process with a nucleus,
i.e. ν e produces an electron (e), ν μ , a muon (μ), and tau neutrino ν τ , its
partner lepton τ . The detection of the partner lepton would therefore be the
signature of the corresponding neutrino having appeared after oscillation of
the ν e . The first type of experiment is called a disappearance type of detection
and the second is called an appearance type. Both are used in experiments being
conducted around the world. The frequency of the oscillation is proportional
to the mass difference square between the two neutrinos. It also depends on
the energy of the neutrinos. So given the energy, one can adjust the distance
where one should observe the neutrinos to detect the oscillation. For a given
energy neutrino beam for very small mass differences, the distances are large,
and for very large mass differences, the distances are small. The first evidence
for neutrino oscillation used natural beams of neutrinos that originate from the
Sun. At the core of the Sun, nuclear reactions that give us light are constantly
producing neutrinos. The Sun is a perfect sphere of hot ionized gas, at a
distance of about 93 million miles from the Earth. It has a surface temperature
of about 5800 K. Its core temperature is about 15 million degrees Kelvin.
Such high temperature in the solar core causes the nuclear and weak force
mediated reactions to take place rapidly. The energy released from The Sun
comes from these weak reactions in which four protons and two electrons fuse
together to produce a helium atom and two neutrinos, along with 26 million
electron volts of energy. This released energy comes to us as sunlight, after
the photons, which carry this energy keep bouncing around from the core
to the surface and come straight at us. They come at all frequencies, starting
from ultraviolet to infrared. The first is responsible for the UV index that we
always watch out for when we go out in the Sun, and the second is what we
are warned about when we are told not to look at the Sun directly. To see if the
oscillation is taking place, one needs to know how many neutrinos are coming
from the solar core in the first place. Astrophysicist John Bahcall performed
valiant calculations during 1960s to measure the number of neutrinos emitted
from the solar core. John Bahcall was born in Shriveport, Louisiana, and got
interested in physics when he was a student at the University of California,
Berkeley, on a tennis scholarship. He once said that, “Physics changed my life.”
He worked with distinguished astrophysicists such as Nobel laureate Willy
Fowler, among others, and became a distinguished astrophysicist himself,
contributing to many areas of the field. But his first love was solar neutrinos. A
R. N. Mohapatra
There are two ways to detect neutrino oscillation: one way is as described
above, where one looks for depletion of the original intensity of the beam, and
a second way where one looks for the appearance of the new kind of neutrino
which the original beam turned partially into. Each neutrino produces its
partner lepton in a weak force mediated scattering process with a nucleus,
i.e. ν e produces an electron (e), ν μ , a muon (μ), and tau neutrino ν τ , its
partner lepton τ . The detection of the partner lepton would therefore be the
signature of the corresponding neutrino having appeared after oscillation of
the ν e . The first type of experiment is called a disappearance type of detection
and the second is called an appearance type. Both are used in experiments being
conducted around the world. The frequency of the oscillation is proportional
to the mass difference square between the two neutrinos. It also depends on
the energy of the neutrinos. So given the energy, one can adjust the distance
where one should observe the neutrinos to detect the oscillation. For a given
energy neutrino beam for very small mass differences, the distances are large,
and for very large mass differences, the distances are small. The first evidence
for neutrino oscillation used natural beams of neutrinos that originate from the
Sun. At the core of the Sun, nuclear reactions that give us light are constantly
producing neutrinos. The Sun is a perfect sphere of hot ionized gas, at a
distance of about 93 million miles from the Earth. It has a surface temperature
of about 5800 K. Its core temperature is about 15 million degrees Kelvin.
Such high temperature in the solar core causes the nuclear and weak force
mediated reactions to take place rapidly. The energy released from The Sun
comes from these weak reactions in which four protons and two electrons fuse
together to produce a helium atom and two neutrinos, along with 26 million
electron volts of energy. This released energy comes to us as sunlight, after
the photons, which carry this energy keep bouncing around from the core
to the surface and come straight at us. They come at all frequencies, starting
from ultraviolet to infrared. The first is responsible for the UV index that we
always watch out for when we go out in the Sun, and the second is what we
are warned about when we are told not to look at the Sun directly. To see if the
oscillation is taking place, one needs to know how many neutrinos are coming
from the solar core in the first place. Astrophysicist John Bahcall performed
valiant calculations during 1960s to measure the number of neutrinos emitted
from the solar core. John Bahcall was born in Shriveport, Louisiana, and got
interested in physics when he was a student at the University of California,
Berkeley, on a tennis scholarship. He once said that, “Physics changed my life.”
He worked with distinguished astrophysicists such as Nobel laureate Willy
Fowler, among others, and became a distinguished astrophysicist himself,
contributing to many areas of the field. But his first love was solar neutrinos. A