IceCube Neutrino Observatory

The IceCube Neutrino Observatory is a neutrino telescope currently under construction at the Amundsen-Scott South Pole Station. [http://www.icecube.wisc.edu/info/] Like its predecessor, the Antarctic Muon And Neutrino Detector Array (AMANDA), IceCube is being constructed in deep Antarctic ice by deploying thousands of spherical optical sensors (photomultiplier tubes, or PMTs) at depths between 1,450 and 2,450 meters. The sensors are deployed on "strings" of sixty modules each, into holes melted in the ice using a hot water drill.

Construction status

In 2005, the first IceCube string was deployed [http://www.spaceref.com/news/viewpr.html?pid=18108 "IceCube - One hole done, 79 more to go" at SpaceRef.com] ] and has collected enough data to verify that the optical sensors work correctly. In the 2005-2006 Austral summer season, an additional eight strings were deployed, making IceCube the largest neutrino telescope in the world. Thirteen strings were installed in the 2006-2007 Austral summer, and eighteen strings were installed in the 2007-2008 Austral summer. Installation is now half complete and is expected to finish in 2011.

Experimental goals

The main goal of the experiment [http://icecube.wisc.edu/pub_and_doc/reviews_and_meetings/June2002_NRC-Review/presentations/nrc_halzen.pdf "IceCube: A Kilometer-Scale Neutrino Observatory", National Research Council IceCube Review Presentation by F. Halzen] (PDF)] is to detect neutrinos in the "high energy" range, which spans (expressed in electron volt) from $10^\{11\}$ to about $10^\{21\}$ eV. The neutrinos are not detected themselves. Instead, the rare instance of a collision between a neutrino and an atom within the ice is used to deduce the kinematical parameters of the incoming neutrino. Current estimates predict the detection of about one thousand such events per day in the fully constructed IceCube detector. Due to the high density of the ice, almost all detected products of the initial collision will be muons. Therefore the experiment is most sensitive to the flux of muon neutrinos through its volume. However, there is a large background of muons created not by neutrinos but by cosmic rays impacting the atmosphere above the detector; most of these can be rejected immediately by virtue of the fact that they are traveling downwards. Most of the remaining (up-going) neutrinos will come from cosmic rays hitting the far side of the Earth, but some unknown fraction may come from astronomical sources. To distinguish these two sources statistically, the direction and energy of the incoming neutrino is estimated from its collision by-products. Unexpected excesses in energy or from a given spatial direction indicate an extraterrestrial source.

Possible tests

Neutrino detection

Although IceCube is expected to detect very few neutrinos, it should have very high resolution with the ones that it does find. According to an Associated Press report, [ [http://www.usatoday.com/tech/science/discoveries/2006-02-17-icecube-project_x.htm USATODAY.com - Scientists find first neutrinos in 'IceCube' project ] ] scientists at the facility believe they have detected their first neutrinos on January 29, 2006. Over several years of operation, it could produce a flux map of the northern hemisphere similar to existing maps like that of the cosmic microwave background. Likewise, KM3NeT could complete the map for the southern hemisphere.

Gamma ray origins

When protons collide with one another or with photons, the result is usually pions. Charged pions decay into neutrinos whereas neutral pions decay into gamma rays. Potentially, the neutrino flux and the gamma ray flux may coincide in certain sources such as gamma ray bursts and supernova remnants, indicating the elusive nature of their origin. Data from IceCube could be used in conjunction with cosmic ray detectors like HESS or MAGIC for this goal.

tring theory

The described detection strategy, along with its South Pole position, could allow the detector to provide the first robust experimental evidence of extra dimensions predicted in string theory. According to the theory, there should exist a sterile neutrino, made from a closed string. These could leak into extra dimensions before returning, making them appear to travel faster than the speed of light. An experiment to test this may be possible in the near future. [ [http://www.newscientist.com/channel/fundamentals/mg19025521.600.html At last, a way to test time travel - fundamentals - 22 May 2006 - New Scientist ] ] Furthermore, if high energy neutrinos create microscopic black holes (as predicted by some aspects of string theory) it would create a shower of particles; resulting in an increase of "down" neutrinos while reducing "up" neutrinos. [ [http://physorg.com/news10295.html South Pole Neutrino Detector Could Yield Evidences of String Theory ] ]

See also

*Antarctic Muon And Neutrino Detector Array
*Radio Ice Cerenkov Experiment

References

External links

* [http://icecube.wisc.edu/ IceCube Home Page]
* [http://amanda.uci.edu/ AMANDA home page]