From Scrying to Neutrino Observation 
IceCube Neutrino Observatory
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"IceCube" redirects here. For the MC and rapper, see Ice Cube. For the item, see Ice cube.
"Taklampa," one of the DOMs of IceCube's hole #85
The IceCube Neutrino Observatory (or simply IceCube) is a neutrino telescope currently under construction at the Amundsen-Scott South Pole Station.[1] Similar to its predecessor, the Antarctic Muon And Neutrino Detector Array (AMANDA), IceCube is being constructed in the deep Antarctic ice by deploying thousands of spherical optical sensors called digital optical modules (DOMs), each with a photomultiplier tube (PMT) and a single board data acquisition computer which sends digital data to the counting house on the surface above the array.[2] The sensors are deployed on "strings" of sixty modules each at depths ranging from 1,450 to 2,450 meters, into holes melted in the ice using a hot water drill. IceCube is designed to look for point sources of neutrinos in the TeV range to explore the highest-energy astrophysical processes.
Contents
[hide]
* 1 Construction status
* 2 Sub-detectors
* 3 Experimental mechanism
* 4 Experimental goals
o 4.1 Point Sources of High Energy Neutrinos
o 4.2 Gamma ray bursts coincident with neutrinos
o 4.3 Indirect dark matter searches
o 4.4 Neutrino oscillations
o 4.5 Galactic Supernovae
o 4.6 String theory
* 5 Results
* 6 See also
* 7 References
* 8 External links
[edit] Construction status
IceCube drilling tower and hose reel in December 2009
In 2005, the first IceCube string was deployed[3] 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 (bringing the total to 22), eighteen strings were installed in the 2007–2008 austral summer (bringing the total to 40 strings, half of the design size), and nineteen strings were installed in the 2008–2009 austral summer (bringing the total to 59 strings). Construction is expected to finish in 2011.
[edit] Sub-detectors
IceCube has several sub-detectors in addition to the main array.
* AMANDA, the Antarctic Muon And Neutrino Detector Array, was the first part built, and it served as a proof-of-concept for IceCube. AMANDA was turned off in April 2009.[citation needed]
* The IceTop array is a series of Cherenkov detectors on the surface of the glacier, two detectors approximately above each IceCube string. IceTop is used as a cosmic ray shower detector, for cosmic ray composition studies and coincident event tests: if a muon is observed going through IceTop, it cannot be from a neutrino interacting in the ice.
* The Deep Core Low-Energy Extension is a densely instrumented region of the IceCube array which extends the observable energies below 100 GeV. The Deep Core strings are deployed at the center (in the surface plane) of the larger array, deep in the clearest ice at the bottom of the array (between 1760 and 2450 m deep). There are no Deep Core DOMs between 1850 m and 2107 m depth, as the ice is not as clear in those layers.
[edit] Experimental mechanism
Neutrinos are electrically neutral leptons, and they very rarely interact. When they do react with the quarks within the ice, they can create charged leptons (electrons, muons, or taus) which, if they are energetic enough, can emit Cherenkov radiation. This happens when the charged particle travels through the ice faster than the speed of light in the ice, similar to the bow shock of a boat traveling faster than the waves it crosses. This light may be detected by photomultiplier tubes within the DOMs making up IceCube. The signals from the photomultiplier tubes are digitized and then sent to the surface of the glacier on a cable. These signals are collected in a surface counting house, and some of them are sent north via satellite for further analysis. More of the data is kept on tape and sent north once a year via ship.
Once the data reach experimenters, they can reconstruct kinematical parameters of the incoming neutrino. High-energy neutrinos may leave a large signal in the detector, pointing back to their origin. Clusters of such neutrino directions indicate point sources of neutrinos.
Each of the above steps requires a certain minimum energy, and thus IceCube is sensitive mostly to high energy neutrinos, in the range of 1011 to about 1021 eV.[4] Current estimates predict a neutrino event about every 20 minutes in the fully constructed IceCube detector.[citation needed]
IceCube is more sensitive to muons than other charged leptons, because they are the most penetrating and thus have the longest tracks in the detector. Thus, of the neutrino flavors, IceCube is most sensitive to muon neutrinos. Electrons typically scatter several times before losing enough energy to fall below the Cherenkov threshold; this means that they cannot typically be used to point back to sources, but they are more likely to be fully contained in the detector, and thus they can be useful for energy studies. These events are more spherical, or "cascade"-like, than track-like; muons are more track-like. Taus can also create cascade events; because of their short lifetime, they cannot travel very far before decaying, and are thus usually indistinguishable from electron cascades.
A tau could be distinguished from an electron with a "double bang" event, where a cascade is seen both at the tau creation and decay. This is only possible with very high energy taus. Hypothetically, to resolve a tau track, the tau would need to travel at least from one DOM to an adjacent DOM (17 m) before decaying. As the average lifetime of a tau is 2.9×10−13 s, a tau travelling at near the speed of light would requires an energy of 20 TeV for every meter traveled.[5] Realistically, an experimenter would need more space than just one DOM to the next to distinguish two cascades, so double bang searches are centered at PeV scale energies. Such searches are under way but have not so far isolated a double bang event from background events.[citation needed]
However, there is a large background of muons created not by neutrinos from astrophysical sources but by cosmic rays impacting the atmosphere above the detector. There are about 106 times more cosmic ray muons than neutrino-induced muons observed in IceCube.[citation needed] Most of these can be rejected using the fact that they are traveling downwards. Most of the remaining (up-going) events are from neutrinos, but most of these neutrinos are from cosmic rays hitting the far side of the Earth; some unknown fraction may come from astronomical sources, and these neutrinos are the key to IceCube point source searches. Current estimates predict the detection of about 75 upgoing neutrinos per day in the fully-constructed IceCube detector. The arrival directions of these astrophysical neutrinos are the points with which the IceCube telescope maps the sky. To distinguish these two types of neutrinos statistically, the direction and energy of the incoming neutrino is estimated from its collision by-products. Unexpected excesses in energy or excesses from a given spatial direction indicate an extraterrestrial source.
[edit] Experimental goals
[edit] Point Sources of High Energy Neutrinos
A point source of neutrinos could help explain the mystery of the origin of the highest energy cosmic rays. These cosmic rays have energies high enough that they cannot be contained by galactic magnetic fields (their gyroradii are larger than the radius of the galaxy), so they are believed to come from extra-galactic sources. Astrophysical events which are cataclysmic enough to create such high energy particles would probably also create high energy neutrinos, which could travel to the Earth with very little deflection, because neutrinos interact so rarely. IceCube could observe these neutrinos: its observable energy range is about 100 GeV (0.1 TeV) to several PeV. The more energetic an event is, the larger volume IceCube may detect it in; in this sense, IceCube is more similar to Cherenkov telescopes like the Pierre Auger Observatory (an array of Cherenkov detecting tanks) than it is to other neutrino experiments, such as Super-K (with inward-facing PMTs fixing the fiducial volume).
IceCube is sensitive to point sources more in the northern hemisphere than the southern. It can observe astrophysical neutrino signals from any direction, but in the southern hemisphere these neutrinos are swamped by the downgoing cosmic-ray muon background. Thus, early IceCube point source searches focus on the northern hemisphere, and the extension to southern hemisphere point sources [6] [7] takes extra work.
Although IceCube is expected to detect very few neutrinos (relative to the number of photons detected by more traditional telescopes), it should have very high resolution with the ones that it does find. 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, or gamma ray telescopes, which use particle terminology more like IceCube. Likewise, KM3NeT could complete the map for the southern hemisphere.
IceCube scientists have detected their first neutrinos on January 29, 2006.[8]
[edit] Gamma ray bursts coincident with neutrinos
When protons collide with one another or with photons, the result is usually pions. Charged pions decay into muons and muon 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 is being used in conjunction with cosmic ray detectors like HESS or MAGIC for this goal. The 22 string setup, "IC22," did not observe any neutrinos in coincidence with GRBs, but was able to use this search to constrain neutrino flux models from GRBs.[9]
[edit] Indirect dark matter searches
Weakly interacting massive particle (WIMP) dark matter could be attracted by the mass of the Sun and collect gravitationally in the core of the Sun. When it reaches a critical mass, it could start annihilating with itself. The decay products of this annihilation could decay into neutrinos, which could be observed by IceCube as an excess of neutrinos from the direction of the Sun. This technique of looking for the decay products of WIMP annihilation is called indirect, as opposed to direct searches which look for dark matter interacting within a contained, instrumented volume. Solar WIMP searches are more sensitive to spin-dependent WIMP models than many direct searches, because the Sun is made of lighter elements than direct search detectors (e.g. xenon or germanium). IceCube has set better limits with the 22 string detector (about 1⁄4 of the full detector) than the AMANDA limits.[10]
[edit] Neutrino oscillations
IceCube can observe neutrino oscillations from atmospheric cosmic ray showers, over a baseline across the Earth. It is most sensitive at ~25 GeV, the energy range which Deep Core will be able to see. IceCube can constrain θ23. Deep Core will have the full 6 strings deployed by the end of the 2009–2010 austral summer. As more data is collected and IceCube can refine this measurement, it may be possible to observe a shift in the oscillation peak that determines the neutrino mass hierarchy. This mechanism for determining the mass hierarchy would only work if θ13 is sufficiently large (close to present limits).
[edit] Galactic Supernovae
Despite the fact that individual neutrinos expected from supernovae have energies well below the IceCube energy cutoff, IceCube could detect a local supernova. It would appear as a detector-wide, brief, correlated rise in noise rates. The supernova would have to be relatively close (within our galaxy) to get enough neutrinos before the 1/r2 distance dependence took over. IceCube is a member of the Supernova Early Warning System (SNEWS).[11]
[edit] String 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.[12] 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.[13] There is not currently a group within the IceCube collaboration working on tachyons, sterile neutrino observation, travel through extra dimensions, or observations of microscopic black holes.
[edit] Results
The IceCube collaboration has published flux limits for neutrinos from point sources,[14] Gamma-ray bursts,[15] and neutralino annihilation in the Sun, with implications for weakly interacting massive particle- (WIMP-) proton cross sections.[16] A shadowing effect from the Moon has been observed.[17][18] cosmic ray protons are blocked by the Moon, creating a deficit of cosmic ray shower muons in the direction of the Moon. A small (under 1%) but robust anisotropy has been observed in cosmic ray muons.[19] suggested an effect similar to the one observed by the Milagro gamma-ray observatory.
[edit] See also
* Deep Core Low-Energy Extension of IceCube
* Antarctic Muon And Neutrino Detector Array
* Radio Ice Cerenkov Experiment
[edit] References
1. ^ "IceCube: Extreme Science!". University of Wisconsin. 30 June 2009.
http://www.icecube.wisc.edu/info/. Retrieved 2009-10-15.
2. ^ R. Abbasi et al. (IceCube Collaboration) (2009). "The IceCube Data Acquisition System: Signal Capture, Digitization, and Timestamping". Nuclear Instruments and Methods A 601: 294–316. doi:10.1016/j.nima.2009.01.001.
3. ^ SpaceRef (24 October 2005). "IceCube - One hole done, 79 more to go". Press release.
http://www.spaceref.com/news/viewpr.html?pid=18108. Retrieved 2009-10-15.
4. ^ F. Halzen (June 2002). "IceCube: A Kilometer-Scale Neutrino Observatory".
http://icecube.wisc.edu/pub_and_doc/reviews_and_meetings/June2002_NRC-Review/presentations/nrc_halzen.pdf. Retrieved 2009-10-15.
5. ^ Speed of light (299,792,458 m/s) × average lifetime (2.9×10−13 s) = 8.711×10−5 m
6. ^ R. Abbasi et al (IceCube Collaboration). "Error: no |title= specified when using {{Cite web}}".
7. ^ R. Abbasi et al (IceCube Collaboration). "Error: no |title= specified when using {{Cite web}}".
8. ^ K. Mizoguchi (17 February 2006). "Scientists find first neutrinos in 'IceCube' project". USA Today.
http://www.usatoday.com/tech/science/discoveries/2006-02-17-icecube-project_x.htm. Retrieved 2009-10-15.
9. ^ R.U. Abbasi et al. (2010). "Search for Muon Neutrinos from Gamma-Ray Bursts with the IceCube Neutrino Telescope". Astrophysical Journal 710: 346-359. doi:10.1088/0004-637X/710/1/346. arΧiv:0907.2227.
10. ^ R. Abbasi et al. (IceCube Collaboration) (2009). "Limits on a muon flux from Kaluza-Klein dark matter annihilations in the Sun from the IceCube 22-string detector". arΧiv:0910.4480 [astro-ph.CO].
11. ^ K. Scholberg (2008). "The SuperNova Early Warning System". arΧiv:0803.0531 [astro-ph].
12. ^ M. Chown (22 May 2006). "At last, a way to test time travel". New Scientist.
http://www.newscientist.com/article/mg19025521.600-at-last-a-way-to-test-time-travel.html. Retrieved 2009-10-15.
13. ^ "South Pole Neutrino Detector Could Yield Evidences of String Theory". PhysOrg.com. 26 January 2006.
http://physorg.com/news10295.html.
14. ^ Abbasi, R. et al. (August 2009). "First Neutrino Point-Source Results from the 22 String Icecube Detector". The Astrophysical Journal Letters 701: L47-L51. doi:10.1088/0004-637X/701/1/L47.
http://adsabs.harvard.edu/abs/2009ApJ...701L..47A.
15. ^ Taboada, I. (May 2009). C. Meegan, C. Kouveliotou, and N. Gehrels. ed. Searches for neutrinos from GRBs with IceCube. American Institute of Physics Conference Series. 1133. pp. 431-433. doi:10.1063/1.3155942.
http://adsabs.harvard.edu/abs/2009AIPC.1133..431T.
16. ^ Abbasi, R. et al. (May 2009). "Limits on a Muon Flux from Neutralino Annihilations in the Sun with the IceCube 22-String Detector". Physical Review Letters 102 (20): 201302-+. doi:10.1103/PhysRevLett.102.201302.
http://adsabs.harvard.edu/abs/2009PhRvL.102t1302A.
17. ^ E. Hand (3 May 2009). "APS 2009: The muon shadow of the Moon". In The Fields.
http://blogs.nature.com/news/blog/2009/05/aps_2009_the_muon_shadow_of_th.html. Retrieved 2009-10-15.
18. ^ 31st International Cosmic Ray Conference, Moon Shadow Observation by IceCube
19. ^ Abbasi, R. and Desiati, P. for the IceCube Collaboration (July 2009). "Large Scale Cosmic Ray Anisotropy With IceCube". ArXiv e-prints.
http://adsabs.harvard.edu/abs/2009arXiv0907.0498A.
[edit] External links
* IceCube Home Page
* AMANDA home page
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My question is, can this thing predict smaller events involving cosmic rays, such as sunspot, solar storms, ejections, how these relate to eartquakes and how we can detect them, etc?
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http://icecube.wisc.edu/Trapping space ghosts
Enormous, frozen detector nets elusive neutrinos
Sunday, May 17, 2009 3:30 AM
By Doug Caruso
THE COLUMBUS DISPATCH
<p>Information from the sensors is sent to the lab above ground.</p>
IceCube Neutrino Observatory
Information from the sensors is sent to the lab above ground.
<a href="
http://www.dispatch.com/live/content/science/stories/2009/05/17/ghost.html">Click here to enlarge</a>
Click here to enlarge
<p>Carsten Rott</p>
Carsten Rott
Born of exploding stars and violent cosmic collisions, neutrinos streak through space -- and planets -- at the speed of light.
You can't see them, and they pass through matter, making them among the slipperiest subatomic particles the cosmos hurls at Earth.
But you can catch neutrinos and get a glimpse of astronomical events that date back billions of years. To do this, researchers are building IceCube, a gigantic detector tucked deep inside the South Pole.
When the detector is completed, it will rest inside a block of ice that measures a kilometer on each side and features more than 5,100 sensors.
Story continues below
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Here's how it works: Every now and then, a cosmic neutrino smacks into a proton in a molecule of water inside the telescope. The collision creates another particle, called a muon, and a tiny flash of blue light that travels in the same line as the neutrino.
The idea is that if you can see where the neutrino was going, you can track where it came from. That opens the door to its history.
Why so large a telescope? Recording a collision between a cosmic neutrino and a water molecule in one spot is such a rare event that you need a huge detector.
"It's like trying to win the lottery," said John Beacom, an Ohio State University physicist who has worked out theories about how likely IceCube is to catch its prey.
"If you buy enough tickets, you're eventually going to win."
An international consortium led by the University of Wisconsin and funded mostly by the U.S. National Science Foundation started construction in 2005.
Last year, as data began to stream in, the consortium accepted Beacom and others at Ohio State University into the project.
Francis Halzen, a physicist at Wisconsin and the primary investigator on IceCube, began pushing for such a device in 1987.
When Halzen pitched IceCube to federal budget officials, one asked him why he wanted to build the detector.
He joked that he could think of 42 reasons to build it, referring to Douglas Adams' Hitchhiker's Guide to the Galaxy, in which the answer to "life, the universe and everything" is "42."
"They didn't get the joke," he said. "They wanted to see the list."
Halzen landed $272 million to get started.
Carsten Rott, a postdoctoral fellow at the OSU Center for Cosmology and Astro-Particle Physics, spent three Antarctic summers building the IceCube telescope.
Right now, there are 59 strings of sensors. When it's complete in two years, it'll have 86.
"It's large enough now to start looking for neutrinos," Rott said.
He and other researchers around the world are already analyzing data from Antarctica, looking for the elusive cosmic neutrino.
Depending on what they're looking for, researchers can filter the data for neutrinos that come from certain angles and speeds.
Some researchers will study data to learn about exploding stars. Rott is using calculations developed by Beacom and others to look for neutrinos that indicate the presence of dark matter in the center of the sun or Earth.
Current theories about dark matter, which makes up most of the mass in the universe, say that particles of dark matter can, by chance, collide with the protons and neutrons in conventional matter in space.
As this happens over billions of years, the dark matter particles slow enough that they can be captured by the gravitational pull of a large object such as the sun or Earth.
As they fly through a star or a planet, the particles are more likely to collide with conventional matter, and slow more, eventually settling into the center. If two particles of dark matter meet there -- b oom!
"They can annihilate and produce other particles," Rott said.
Most of those would be absorbed. But neutrinos would likely make it out and maybe, just maybe, collide with a water molecule in a huge block of ice in Antarctica.
That would be cool, but the most exciting discovery might follow neutrinos that enter the detector from a dark part of the universe where no conventional telescope has ever spotted anything.
"In our wildest dreams we find something that we haven't thought of," Halzen said. "Something totally unexpected."
dcaruso@dispatch.comB
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Ontario neutrino detector not accurate enough or what?
When it’s completed in 2011, the South Pole neutrino observatory, Ice Cube, promises to open a new window on otherworldly events happening across the universe, such as colliding galaxies and black holes. In the meantime, though, it’s producing some decidedly down-to-earth results for Wisconsin.
Since construction began in 2002, $77 million has been spent in the state to design, engineer and build IceCube components, including a special hot-water drill for boring deep into the Antarctic ice, and more than 5,000 optical sensors, whose job is to detect cosmic particles, called neutrinos, with origins in deep space.
