192
R. N. Mohapatra
25.3 Neutrinos Observed in the IceCube
Experiment in the South Pole
A major effort to look for more energetic neutrinos has been launched with
an experimental setup, called IceCube, in the South Pole. Located at the
Amundsen–Scott South Pole station in Antarctica, the setup has thousands of
sensors under the ice. The sensors, digital optical modules which have photo
multipliers inside them, are buried deep under clear ice to detect light emitted
from passing electrons and muons, etc. They are attached to strings, with each
string containing about 60 photo-multipliers. They go down to a depth of
one and a half to two and a half kilometers. The construction began in 2005
during the Antarctica summer, from November to February when there is 24 h
sunlight.
The IceCube is essentially a kilometer cube huge water detector for neutrino
interactions, and in some sense is the largest detector on Earth for neutrinos. If
an energetic neutrino comes by, it will create a corresponding charged leptons
(e, μ) by the inverse beta decay process. The (e, μ) traveling fast through the
ice will create Cherenkov light that can be detected by the photomultipliers
in the strings. IceCube has detected more than 50,000 neutrinos per year and
observed 60 extremely high energy neutrino events with energy larger than 60
TeV (60,000 times the proton mass), some with energies of about a million
GeV (called a PeV). The origin of PeV neutrinos is still theoretically unclear
and it has inspired a lot of research in the theoretical area to find out where
they came from.
The IceCube experiment has also detected neutrinos from a class of massive
astronomical objects called blazars. The blazars are active galactic nuclei,
powered by supermassive black holes at the center of galaxies like ours,
which are spewing jets of material towards us. They emit extremely energetic
radiation, which was detected by the Fermi Large Area telescope (FermiLat)
orbiting the Earth, at the same time that the neutrinos were detected. They
were coming from the blazar TXS 0506+056 which is 3.7 light years away.
Every time a black hole gobbles up a star, it emits both energetic radiation as
well as energetic neutrinos. Many thousand blazars have been detected, but
neutrinos from one of them were first detected in 2017.
After the sun and supernova 1987A, the blazars are the third kind of
astronomical objects that we have seen neutrinos from. These are much more
energetic neutrinos than the solar or supernova neutrinos. Their energies are
roughly 40 times that of the LHC energies at about 500 Terra electron volt.
R. N. Mohapatra
25.3 Neutrinos Observed in the IceCube
Experiment in the South Pole
A major effort to look for more energetic neutrinos has been launched with
an experimental setup, called IceCube, in the South Pole. Located at the
Amundsen–Scott South Pole station in Antarctica, the setup has thousands of
sensors under the ice. The sensors, digital optical modules which have photo
multipliers inside them, are buried deep under clear ice to detect light emitted
from passing electrons and muons, etc. They are attached to strings, with each
string containing about 60 photo-multipliers. They go down to a depth of
one and a half to two and a half kilometers. The construction began in 2005
during the Antarctica summer, from November to February when there is 24 h
sunlight.
The IceCube is essentially a kilometer cube huge water detector for neutrino
interactions, and in some sense is the largest detector on Earth for neutrinos. If
an energetic neutrino comes by, it will create a corresponding charged leptons
(e, μ) by the inverse beta decay process. The (e, μ) traveling fast through the
ice will create Cherenkov light that can be detected by the photomultipliers
in the strings. IceCube has detected more than 50,000 neutrinos per year and
observed 60 extremely high energy neutrino events with energy larger than 60
TeV (60,000 times the proton mass), some with energies of about a million
GeV (called a PeV). The origin of PeV neutrinos is still theoretically unclear
and it has inspired a lot of research in the theoretical area to find out where
they came from.
The IceCube experiment has also detected neutrinos from a class of massive
astronomical objects called blazars. The blazars are active galactic nuclei,
powered by supermassive black holes at the center of galaxies like ours,
which are spewing jets of material towards us. They emit extremely energetic
radiation, which was detected by the Fermi Large Area telescope (FermiLat)
orbiting the Earth, at the same time that the neutrinos were detected. They
were coming from the blazar TXS 0506+056 which is 3.7 light years away.
Every time a black hole gobbles up a star, it emits both energetic radiation as
well as energetic neutrinos. Many thousand blazars have been detected, but
neutrinos from one of them were first detected in 2017.
After the sun and supernova 1987A, the blazars are the third kind of
astronomical objects that we have seen neutrinos from. These are much more
energetic neutrinos than the solar or supernova neutrinos. Their energies are
roughly 40 times that of the LHC energies at about 500 Terra electron volt.