Electron
Bubble Particle Detector
Neutrino physics
- The Neutrino
and its friends
are one of the fundamental particles which make up the universe. They
are also one of the least understood. Neutrinos are similar to the more
familiar electron, with one crucial difference: neutrinos do not carry
electric charge. Because neutrinos are electrically neutral, they are
not affected by the electromagnetic forces which act on electrons.
Neutrinos are affected only by a "weak"
sub-atomic force
of much shorter range than electromagnetism, and are therefore able to
pass through great distances in matter without being affected by it. If
neutrinos have mass, they also interact gravitationally with other
massive particles, but gravity is by far the weakest of the four known
forces.
- Three types of neutrinos are known; there is strong
evidence that no additional neutrinos exist, unless their properties
are unexpectedly very different from the known types. Each type or
"flavor" of neutrino is related to a charged particle (which gives the
corresponding neutrino its name). Hence, the "electron neutrino" is
associated with the electron, and two other neutrinos are associated
with heavier versions of the electron called the muon and the tau
(elementary particles are frequently labelled with Greek letters, to
confuse the layman). Click here
for a list of the known types of neutrinos (and their electrically
charged partner). For more information, see Neutrino
History and Main
Contributors.
- For more than three decades, underground experiments
measuring the flux of neutrinos from the Sun have found a significant
deficit in the observed rate compared to the predictions of the
Standard Model (SM). A possible explanation for this discrepancy is
that neutrinos produced in the core of the Sun are modified along their
path to Earth, transforming into another neutrino species via neutrino
oscillations. The next major goal of solar neutrino astronomy is to
measure neutrino fluxs in low energy region less than 1MeV, and in
particular to measure the flux from the dominant pp reaction,
which peaks in the range of 200-300 keV. It would be very desirable to
measure also the energy spectrum of the scattered electrons produced by
neutrino interactions. They will provide a simultaneous and critical
test of stellar evolution and of neutrino oscillations. For more
information, see Neutrino
Oscillation Industry.