Research Objectives:
This project is an international collaboration to build a neutrino telescope over the next six austral summers. Neutrinos are subatomic particles produced by the decay of radioactive elements and elementary particles such as pions. The existence of neutrinos was first suspected in 1930 when scientists observed that energy and momentum were missing from the decay of radioactive nuclei. In 1955 neutrinos were finally observed and in 2001 experiments observing the sun revealed that neutrinos have tiny but definitely non-zero masses.
Neutrinos are difficult to observe since they rarely interact with matter. It is this feeble interaction that makes them uniquely valuable as astronomical messengers from outside the solar system. Unlike photons or charged particles, neutrinos can emerge from deep inside their sources and travel across the universe without interference. They are not deflected by interstellar magnetic fields and are not absorbed by intervening matter. However, this same trait makes cosmic neutrinos extremely difficult to detect; immense instruments are required to find them in sufficient numbers to trace their origin.
On the rare occasions when a neutrino does collide with a terrestrial atom, it produces a particle called a “muon.” The muon emits Cherenkov radiation that is detectable as blue light. The muon preserves the direction of the original neutrino, thus pointing back to its cosmic source. By detecting this light, scientists can reconstruct the muon’s, and hence the neutrino’s, path.
The IceCube observatory will be a cubic kilometer-sized array of 4,200 photomultiplier tubes deployed on 70 vertical strings and buried 1.4 to 2.4 kilometers deep in the ice. AMANDA (Antarctic Muon and Neutrino Detector Array, Bob Morse, A-130-S) has served as a prototype for the new, larger array. Antarctic polar ice is an ideal medium for detecting neutrinos because it is exceptionally pure, transparent, and free of radioactivity. The blue light of Cherenkov radiation travels a hundred meters or more through the ultra-transparent ice.
Looking through the earth for neutrinos from outside the solar system, IceCube will detect subatomic particles from the most violent astrophysical sources: Events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature.
