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'''Geoneutrino''' is an electron [[Neutrino|antineutrino]] emitted in [[Beta decay|{{SubatomicParticle|Beta-}} decay]] of a [[radionuclide]] naturally occurring in the [[Earth]]. Neutrinos, the lightest of the known [[subatomic particles]], lack measurable electromagnetic properties and interact only via the [[Weak interaction|weak nuclear force]]. Matter is virtually transparent to neutrinos and consequently they travel, unimpeded, at near light speed through the Earth from their point of emission. Collectively, geoneutrinos carry integrated information about the abundances of their radioactive sources inside the Earth. A major objective of the emerging field of '''neutrino geophysics''' involves extracting geologically useful information (e.g., abundances of individual geoneutrino-producing elements and their spatial distribution in Earth’s interior) from geoneutrino measurements.

Most geoneutrinos originate from {{SubatomicParticle|Beta-}} decay-branches of [[potassium-40|40K]], [[thorium-232|232Th]] and [[uranium-238|238U]]. Together these [[decay chain]]s account for more than 99% of the present-day [[radiogenic heat]] generated inside the Earth. Only geoneutrinos from 232Th and 238U decay chains are detectable by the [[Cowan–Reines neutrino experiment|inverse beta-decay]] mechanism because these have energies above the corresponding threshold (1.8 [[megaelectronvolt|MeV]]). In neutrino experiments, large underground liquid [[scintillator]] detectors record the flashes of light generated from this interaction. {{As of | 2013}} geoneutrino measurements at two sites, as reported by the [[KamLAND]] and [[Borexino]] collaborations, have begun to place constraints on the amount of radiogenic heating in the Earth's interior. A third detector ([[SNO+]]) is expected to start collecting data in 2013. A number of future geoneutrino detectors are being planned.

==History==
[[File:Beta Negative Decay.svg|thumb|The [[Feynman diagram]] for [[Beta decay|{{SubatomicParticle|Beta-}} decay]] of a [[neutron]] into a [[proton]], [[electron]], and [[electron antineutrino]] via an intermediate [[W boson|{{SubatomicParticle|W boson-}} boson]].]]
[[Neutrinos]] were hypothesized in 1930 by [[Wolfgang Pauli]]. The first detection—of antineutrinos generated in a nuclear reactor—was confirmed in 1956.<ref name=cowan56>{{cite journal|last=Cowan|first=C. L.|coauthors=Reines, F.; Harrison, F. B.; Kruse, H. W.; McGuire, A. D.|title=Detection of the free neutrino: a confirmation|journal=Science|year=1956|volume=124|issue=3212|pages=103–662|doi=10.1126/science.124.3212.103|pmid=17796274|bibcode = 1956Sci...124..103C }}</ref> The idea of studying geologically produced neutrinos to infer Earth’s composition has been around since at least mid-1960s.<ref name=eder66>{{cite journal|last=Eder|first=G.|title=Terrestrial neutrinos|journal=Nuclear Phys.|year=1966|volume=78|issue=3|pages=657–662|doi=10.1016/0029-5582(66)90903-5|bibcode = 1966NucPh..78..657E }}</ref> In a 1984 landmark paper [[Lawrence M. Krauss|Krauss]], [[Sheldon Lee Glashow|Glashow]] & [[David Schramm (astrophysicist)|Schramm]] presented calculations of the predicted geoneutrino flux and discussed the possibilities for detection.<ref name=krauss84>{{cite journal|last=Krauss|first=L. M.|coauthors=Glashow, S. L.; Schramm, D. N.|title=Antineutrino astronomy and geophysics|journal=Nature|year=1984|volume=310|issue=5974|pages=191–198|doi=10.1038/310191a0|bibcode = 1984Natur.310..191K }}</ref> First detection of geoneutrinos was reported in 2005 by the [[KamLAND]] experiment at the [[Kamioka Observatory]] in Japan.<ref name=araki05>{{cite journal|last=Araki|first=T|coauthors=et al.|title=Experimental investigation of geologically produced antineutrinos with KamLAND|journal=Nature|year=2005|volume=436|issue=7050|pages=499–503|doi=10.1038/nature03980|pmid=16049478|bibcode = 2005Natur.436..499A }}</ref><ref name=nyt05>{{cite news|last=Overbye|first=D.|title=Baby Oil and Benzene Provide Look at Earth's Radioactivity|url=http://www.nytimes.com/2005/07/28/science/28neutrino.html|accessdate=9 January 2013|newspaper=New York Times|date=July 28, 2005}}</ref> In 2010 the [[Borexino]] experiment at the [[Gran Sasso National Laboratory]] in Italy released their geoneutrino measurement.<ref name=bellini10>{{cite journal|last=Borexino Collaboration|title=Observation of geo-neutrinos|journal=Phys. Lett. B|year=2010|volume=687|issue=4-5|pages=299–304|doi=10.1016/j.physletb.2010.03.051|arxiv = 1003.0284 |bibcode = 2010PhLB..687..299B }}</ref><ref name=physorg10>{{cite news|last=Edwards|first=L.|title=Borexino experiment detects geo-neutrinos|url=http://phys.org/news187946006.html|accessdate=9 January 2013|newspaper=PhysOrg.com|date=March 16, 2010}}</ref> Updated results from KamLAND were published in 2011.<ref name=gando11>{{cite journal|last=The KamLAND Collaboration|title=Partial radiogenic heat model for Earth revealed by geoneutrino measurements|journal=Nature Geoscience |year=2011|volume=4|issue=9|pages=647–651|doi=10.1038/ngeo1205|bibcode = 2011NatGe...4..647K }}</ref><ref name=scidaily11>{{cite news|title=What Keeps Earth Cooking?|url=http://www.sciencedaily.com/releases/2011/07/110717134819.htm|accessdate=9 January 2013|newspaper=ScienceDaily|date=July 18, 2011}}</ref>

===Geoneutrino science meetings===
A number of scientific meetings focused on neutrino geophysics took place:
* ''[http://www.phys.hawaii.edu/~sdye/hnsc.html Neutrino Sciences 2005]'', Neutrino Geophysics, Honolulu, Hawaii, 14–16 December 2005
* Union Session U41F – ''Geoneutrinos: A New Tool for the Study of the Solid Earth I'', AGU 2006 Joint Assembly, Baltimore, Maryland, 23–26 May 2006 ([http://www.agu.org/cgi-bin/sessions5?meeting=sm06&part=U41F&maxhits=400 session information])
* ''[http://www.phys.hawaii.edu/~sdye/hano.html Neutrino Sciences 2007]'', Deep Ocean Anti-Neutrino Observatory Workshop, Honolulu, Hawaii, 23–25 March 2007
* ''[http://geonu.snolab.ca/ Neutrino Geoscience 2008]'' at SNOLAB, Sudbury, Ontario, Canada, 17–19 September 2008
* ''[http://geoscience.lngs.infn.it/ Neutrino Geoscience 2010]'', Gran Sasso National Laboratory, Italy, 6–8 October 2010
* Neutrino Geoscience Workshop at [http://www.dsu.edu/research/cetup/2011.aspx CETUP* 2011], Deadwood, South Dakota, 20–22 June 2011
* ''[http://www.awa.tohoku.ac.jp/geoscience2013/ Neutrino Geoscience 2013]'', Takayama, Japan, 21–23 March 2013 (planned)

==Geophysical motivation==
{| class="wikitable" style="float: right; clear: right; margin-left: 2em;"
|+ '''Geologically significant antineutrino- and heat-producing radioactive decays and decay chains'''<ref name=dye12>{{cite journal|last=Dye|first=S. T.|title=Geoneutrinos and the radioactive power of the Earth|journal=Rev. Geophys.|year=2012|volume=50|issue=3|pages=RG3007|doi=10.1029/2012RG000400|bibcode=2012RvGeo..50.3007D|arxiv = 1111.6099 }}</ref>
|-
| <math>
\begin{array}{rcl}
_{~92}^{238}\text{U} & \longrightarrow & _{~82}^{206}\text{Pb} + 8\alpha + 6e^- + 6\bar\nu_e + 51.698\,\text{MeV} \\
_{~92}^{235}\text{U} & \longrightarrow & _{~82}^{207}\text{Pb} + 7\alpha + 4e^- + 4\bar\nu_e + 46.402\,\text{MeV} \\
_{~90}^{232}\text{Th} & \longrightarrow & _{~82}^{208}\text{Pb} + 6\alpha + 4e^- + 4\bar\nu_e + 42.652\,\text{MeV} \\
_{19}^{40}\text{K} & \stackrel{89.3\,\%}{\longrightarrow} & _{20}^{40}\text{Ca} + e^- + \bar\nu_e + 1.311\,\text{MeV} \\
_{19}^{40}\text{K} + e^- & \stackrel{10.7\,\%}{\longrightarrow} & _{18}^{40}\text{Ar} + \nu_e + 1.505\,\text{MeV}
\end{array}
</math>
|}
The [[Earth]]'s interior radiates heat at a rate of about 47 TW ([[terawatts]]),<ref name=davies10>{{cite journal|last=Davies|first=J. H.|coauthors=Davies, D. R.|title=Earth's surface heat flux|journal=Solid Earth|year=2010|volume=1|issue=1|pages=5–24|doi=10.5194/se-1-5-2010}}</ref> which is less than 0.1% of the incoming solar energy. Part of this heat loss is accounted for by the heat generated upon decay of radioactive isotopes in the Earth interior. The remaining heat loss is due to the secular cooling of the Earth, growth of the Earth’s [[inner core]] (gravitational energy and latent heat contributions), and other processes. The most important heat-producing elements are [[uranium]] (U), [[thorium]] (Th), and [[potassium]] (K). The debate about their abundances in the Earth has not concluded. Various compositional estimates exist where the total Earth’s internal radiogenic heating rate ranges from as low at ~10 TW to as high as ~30 TW. About 7 TW worth of heat-producing elements reside in the [[Earth crust|Earth's crust]],<ref name=huang13>{{cite journal|last=Huang|first=Y.|coauthors=Chubakov, V.; Mantovani, M.; Rudnick, R. L.; McDonough, W. F.|title=A reference Earth model for the heat producing elements and associated geoneutrino flux|year=2013|arxiv=1301.0365|bibcode = 2013arXiv1301.0365H }}</ref> the remaining power is distributed in the [[Earth mantle]]; the amount of U, Th, and K in the [[Earth core]] is probably negligible. Radioactivity in the Earth mantle provides internal heating to power [[mantle convection]], which is the driver of [[plate tectonics]]. The amount of mantle radioactivity and its spatial distribution—is the mantle compositionally uniform at large scale or composed of distinct reservoirs?—is of importance to geophysics.

The existing range of compositional estimates of the Earth reflects our lack of understanding of what were the processes and building blocks ([[Chondrite|chondritic meteorites]]) that contributed to its formation. More accurate knowledge of U, Th, and K abundances in the Earth interior would improve our understanding of present-day Earth dynamics and of Earth formation in early [[Solar System]]. Counting antineutrinos produced in the Earth can constrain the geological abundance models. The weakly interacting geoneutrinos carry information about their emitters’ abundances and location in the entire Earth volume, including the deep Earth. Extracting compositional information about the Earth mantle from geoneutrino measurements is difficult but possible. It requires a synthesis of geoneutrino experimental data with geochemical and geophysical models of the Earth. Existing geoneutrino data are a byproduct of antineutrino measurements with detectors designed primarily for fundamental neutrino physics research. Future experiments devised with a geophysical agenda in mind would benefit geoscience. Proposals for such detectors have been put forward.<ref name=hanohano08>{{cite journal|last=Learned|first=J. G.|coauthors=Dye, S. T.; Pakvasa, S.|title=Hanohano: A Deep Ocean Anti-Neutrino Detector for Unique Neutrino Physics and Geophysics Studies|year=2008|journal=Published in the Proceedings of the Twelfth International Workshop on Neutrino Telescopes, Venice, March 2007|arxiv=0810.4975|bibcode = 2008arXiv0810.4975L }}</ref>

==Geoneutrino prediction==
[[File:Geoneutrino signal prediction - rotating globe.gif|thumb|Geoneutrino signal prediction at Earth's surface in terrestrial neutrino units (TNU).]]
Calculations of the expected geoneutrino signal predicted for various Earth reference models are an essential aspect of neutrino geophysics. In this context, "Earth reference model" means the estimate of heat producing element (U, Th, K) abundances and assumptions about their spatial distribution in the Earth, and a model of Earth’s internal density structure. By far the largest variance exists in the abundance models where several estimates have been put forward. They predict a total radiogenic heat production as low as ~10 TW<ref name=oneill08>{{cite journal|last=O'Neill|first=H. St. C.|coauthors=Palme, H.|title=Collisional erosion and the non-chondritic composition of the terrestrial planets|journal=Phil. Trans. R. Soc. Lond. A|year=2008|volume=366|issue=1883|pages=4205–4238|doi=10.1098/rsta.2008.0111|bibcode = 2008RSPTA.366.4205O }}</ref><ref name=javoy10>{{cite journal|last=Javoy|first=M.|coauthors=et al.|title=The chemical composition of the Earth: Enstatite chondrite models|journal=Earth Planet. Sci. Lett.|year=2010|volume=293|issue=3-4|pages=259–268|doi=10.1016/j.epsl.2010.02.033|bibcode=2010E&PSL.293..259J}}</ref> and as high as ~30 TW,<ref name=TS02>{{cite book|last=Turcotte|first=D. L.|title=Geodynamics, Applications of Continuum Physics to Geological Problems|year=2002|publisher=Cambridge University Press|isbn=978-0521666244|coauthors=Schubert, G.}}</ref> the commonly employed value being around 20 TW.<ref name=hart86>{{cite journal|last=Hart|first=S. R.|coauthors=Zindler, A.|title=In search of a bulk-Earth composition|journal=Chem. Geol.|year=1986|volume=57|issue=3-4|pages=247–267|doi=10.1016/0009-2541(86)90053-7}}</ref><ref name=mcdonough95>{{cite journal|last=McDonough|first=W. F.|coauthors=Sun, S.-s.|title=The composition of the Earth|journal=Chem. Geol.|year=1995|volume=120|issue=3-4|pages=223–253|doi=10.1016/0009-2541(94)00140-4}}</ref><ref name=oneill03>{{cite journal|last=Palme|first=H.|coauthors=O'Neill, H. St. C.|title=Cosmochemical estimates of mantle composition|year=2003|volume= 2|journal=Treatise on Geochemistry|issue=ch. 2.01|pages=1–38|doi=10.1016/B0-08-043751-6/02177-0|bibcode = 2003TrGeo...2....1P }}</ref> A density structure dependent only on the radius (such as the [[Preliminary Reference Earth Model]] or PREM) with a 3-D refinement for the emission from the Earth’s crust is generally sufficient for geoneutrino predictions.

The geoneutrino signal predictions are crucial for two main reasons: 1) they are used to interpret geoneutrino measurements and test the various proposed Earth compositional models; 2) they can motivate the design of new geoneutrino detectors. The typical geoneutrino flux at Earth's surface is few × 106 cm−2 s−1. As a consequence of i) high enrichment of continental crust in heat producing elements (~7 TW of radiogenic power) and ii) the dependence of the flux on 1/(distance from point of emission)2, the geoneutrino signal pattern correlates well with the distribution of continents. At continental sites, most geoneutrinos are produced locally in the crust. This calls for an accurate crustal model, both in terms of composition and density, a nontrivial task.

Antineutrino emission from a volume V is calculated for each radionuclide from the following equation:

:<math>
\frac{\mathrm{d}\phi(E_{\bar\nu_e},\vec{r})}{\mathrm{d}E_{\bar\nu_e}} = 10\frac{\lambda X N_A}{M} \frac{\mathrm{d}n(E_{\bar\nu_e})}{\mathrm{d}E_{\bar\nu_e}} \int\limits_V \mathrm{d}^3\vec{r}' \frac{A(\vec{r}') \rho(\vec{r}') P_{ee} (E_{\bar\nu_e},|\vec{r}-\vec{r}'|)}{4\pi |\vec{r}-\vec{r}'|^2}
</math>

where dφ(Eν,r)/dEν is the fully oscillated antineutrino flux energy spectrum (in cm−2 s−1 MeV−1) at position r (units of m) and Eν is the antineutrino energy (in MeV). On the right-hand side, ρ is rock density (in kg m−3), A is elemental abundance (kg of element per kg of rock) and X is the natural isotopic fraction of the radionuclide (isotope/element), M is atomic mass (in g mol−1), NA is [[Avogadro's number]] (in mol−1), λ is decay constant (in s−1), dn(Eν)/dEν is the antineutrino intensity energy spectrum (in MeV−1, normalized to the number of antineutrinos nν produced in a decay chain when integrated over energy), and Pee(Eν,L) is the antineutrino survival probability after traveling a distance L.
For an emission domain the size of the Earth, the fully oscillated energy-dependent survival probability Pee can be replaced with a simple factor ⟨Pee⟩≈0.55,<ref name=dye12 /><ref name=fiorentini12>{{cite journal|last=Fiorentini|first=G|coauthors=Fogli, G. L.; Lisi, E.; Mantovani, F.; Rotunno, A. M.|title=Mantle geoneutrinos in KamLAND and Borexino|journal=Phys. Rev. D|year=2012|volume=86|issue=3|pages=033004|doi=10.1103/PhysRevD.86.033004|arxiv = 1204.1923 |bibcode = 2012PhRvD..86c3004F }}</ref> the average survival probability. Integration over the energy yields the total antineutrino flux (in cm−2 s−1) from a given radionuclide:

:<math>
\phi(\vec{r}) = 10\frac{n_{\bar\nu_e} \langle P_{ee} \rangle \lambda X N_A}{M} \int\limits_V \mathrm{d}^3\vec{r}' \frac{A(\vec{r}') \rho(\vec{r}')}{4\pi |\vec{r}-\vec{r}'|^2}
</math>

The total geoneutrino flux is the sum of contributions from all antineutrino-producing radionuclides. The geological inputs—the density and particularly the elemental abundances—carry a large uncertainty. The uncertainty of the remaining nuclear and particle physics parameters is negligible compared to the geological inputs.

==Geoneutrino detection==

===Detection mechanism===
Instruments that measure geoneutrinos are large-size [[Neutrino detector#Scintillators|scintillation detectors]]. They use the ''inverse beta decay'' reaction, a method proposed by [[Bruno Pontecorvo]] that [[Frederick Reines]] and [[Clyde Cowan]] employed in their [[Cowan–Reines neutrino experiment|pioneering experiments in 1950s]]. Inverse beta decay is a charged current weak interaction, where an electron antineutrino interacts with a [[proton]], producing a [[positron]] and a [[neutron]]:

:<math>\bar\nu_e + p \rightarrow e^+ + n</math>

Only antineutrinos with energies above the kinematic threshold of 1.804 MeV—the difference between rest mass energies of neutron plus positron and proton—can participate in this interaction. The positron promptly [[Electron–positron annihilation|annihilates]] with an electron:

:<math>e^+ + e^- \rightarrow \gamma + \gamma</math>

With a delay of few tens to few hundred microseconds the neutron combines with a proton to form a [[deuteron]]:

:<math>n + p \rightarrow d + \gamma</math>

The two light flashes associated with the positron annihilation and the deuteron formation are coincident in time and in space, which provides a powerful method to reject single-flash (non-antineutrino) background events in the liquid scintillator. Antineutrinos produced in man-made nuclear reactors overlap in energy range with geologically produced antineutrinos and are also counted by these detectors.

Because of the kinematic threshold of this antineutrino detection method, only the highest energy geoneutrinos from 232Th and 238U decay chains can be detected. Geoneutrinos from 40K decay have energies below the threshold and cannot be detected using inverse beta decay reaction. Experimental particle physicists are developing other detection methods, which are not limited by an energy threshold (e.g., antineutrino scattering on electrons) and thus would allow detection of geoneutrinos from potassium decay.

Geoneutrino measurements are often reported in ''Terrestrial Neutrino Units'' (TNU; analogy with [[Solar neutrino unit|Solar Neutrino Units]]) rather than in units of flux (cm−2 s−1). TNU is specific to the inverse beta decay detection mechanism with protons. 1 TNU corresponds to 1 geoneutrino event recorded over a year-long fully efficient exposure of 1032 free protons, which is approximately the number of free protons in a 1 kiloton liquid scintillation detector. The conversion between flux units and TNU depends on the thorium to uranium abundance ratio (Th/U) of the emitter. For Th/U=4.0 (a typical value for the Earth), a flux of 1.0 × 106 cm−2 s−1 corresponds to 8.9 TNU.<ref name=dye12 />

===Detectors and results===
[[File:KamLAND schematic.png|thumb|Schematic of the [[KamLAND]] antineutrino detector.]]

====Existing detectors====
[[KamLAND]] (Kamioka Liquid Scintillator Antineutrino Detector) is a 1.0 kiloton detector located at the [[Kamioka Observatory]] in Japan. Results based on detector live-time of 749 days and presented in 2005 mark the first detection of geoneutrinos. The total number of detected antineutrino events was 152, of which geoneutrinos were 4.5 to 54.2 (90% confidence interval) with a central value of 28.0. This analysis put a 60 TW upper limit (99% confidence level) on the Earth’s radiogenic power from 232Th and 238U.<ref name=araki05 />

A 2011 update of KamLAND’s result used data from 2135 days of detector live-time and benefited from improved purity of the scintillator as well as a reduced reactor antineutrino background (21-month long shutdown of the [[Kashiwazaki-Kariwa Nuclear Power Plant|Kashiwazaki-Kariwa nuclear power plant]] after the [[2007 Chūetsu offshore earthquake|July 2007 Chūetsu earthquake]]). Of 841 candidate antineutrino events, 106 (+29/−28 asymmetric error) were identified as geoneutrino using unbinned maximum likelihood analysis with Th/U ratio fixed at 3.9. It was found that 232Th and 282U together generate 20.0 (+8.8/−8.6) TW of radiogenic power.<ref name=gando11 />

[[Borexino]] is a 0.3 kiloton detector at [[Laboratori Nazionali del Gran Sasso]] near [[L'Aquila]], Italy. Results published in 2010 used data collected over live-time of 537 days. Of 15 candidate events, unbinned maximum likelihood analysis identified 9.9 (+4.1/−3.4) as geoneutrinos. Geoneutrino null hypothesis was rejected at 99.997% confidence level (4.2σ). The data also rejected a hypothesis of an active georeactor in the Earth’s core with power above 3 TW at 95% confidence level.<ref name=bellini10 />

'''[[SNO+]]''' is a 0.8 kiloton detector located at [[SNOLAB]] near [[Greater Sudbury|Sudbury]], Ontario, Canada. SNO+ uses the original [[SNO]] experiment chamber. The detector is currently being refurbished and is expected to become operational in 2013.

====Planned and proposed detectors====
* '''[[Low Energy Neutrino Astronomy|LENA]]''' (Low Energy Neutrino Astronomy, [http://www.e15.ph.tum.de/research_and_projects/lena/ website]) is a proposed 50 kiloton liquid scintillation detector of the [[Large Apparatus studying Grand Unification and Neutrino Astrophysics|LAGUNA]] project. Proposed sites include [[Centre for Underground Physics in Pyhäsalmi]] (CUPP), Finland (preferred) and Laboratoire Souterrain de Modane (LSM) in Fréjus, France.<ref name=wurm12>{{cite journal|last=Wurm|first=M.|coauthors=et al.|title=The next-generation liquid-scintillator neutrino observatory LENA|journal=Astroparticle Physics|year=2012|volume=35|issue=11|pages=685–732|doi=10.1016/j.astropartphys.2012.02.011|arxiv = 1104.5620 |bibcode = 2012APh....35..685W }}</ref>
* at [[Deep Underground Science and Engineering Laboratory|DUSEL]] (Deep Underground Science and Engineering Laboratory) at [[Homestake Mine (South Dakota)|Homestake]] in Lead, South Dakota, USA<ref name=tolich06>{{cite journal|last=Tolich|first=N.|coauthors=et al.|title=A Geoneutrino Experiment at Homestake|journal=Earth, Moon, Planets|year=2006|volume=99|issue=1|pages=229–240|doi=10.1007/s11038-006-9112-8|arxiv = physics/0607230 |bibcode = 2006EM&P...99..229T }}</ref>
* at [[Baksan Neutrino Observatory|BNO]] (Baksan Neutrino Observatory) in Russia<ref name=barabanov09>{{cite journal|last=Barabanov|first=I. R.|coauthors=Novikova, G. Ya.; Sinev, V. V.; Yanovich, E. A.|title=Research of the natural neutrino fluxes by use of large volume scintillation detector at Baksan|year=2009|arxiv=0908.1466|bibcode = 2009arXiv0908.1466B }}</ref>
* at Daya Bay-II experiment in China
* [http://www.geoneutrino.nl/ '''EARTH'''] (Earth AntineutRino TomograpHy)
* [http://www.phys.hawaii.edu/~jgl/hanohano.html '''Hanohano'''] (Hawaii Anti-Neutrino Observatory) is a proposed deep-ocean transportable detector. It is the only detector designed to operate away from the Earth's continental crust and from nuclear reactors in order to increase the sensitivity to geoneutrinos from the Earth's mantle.<ref name=hanohano08 />

====Desired future technologies====
* ''Directional antineutrino detection.'' Resolving the direction from which an antineutrino arrived would help discriminate between the crustal geoneutrino and reactor antineutrino signal (most antineutrinos arriving near horizontally) from mantle geoneutrinos (much wider range of incident dip angles).
* ''Detection of antineutrinos from 40K decay.'' Since the energy spectrum of antineutrinos from 40K decay falls entirely below the threshold energy of inverse beta decay reaction (1.8 MeV), a different detection mechanism must be exploited, such as antineutrino scattering on electrons.

==References==
{{reflist}}

==Further reading==
* {{cite book|title=Neutrino Geophysics: Proceedings of Neutrino Sciences 2005|year=2007|publisher=Springer|location=Dordrecht, The Netherlands|isbn=978-0-387-70766-2|url=http://dx.doi.org/10.1007/978-0-387-70771-6|editor=Dye, S. T.}}
* {{cite journal|last=McDonough|first=W. F.|coauthors=Learned, J. G.; Dye, S. T.|title=The many uses of electron antineutrinos|journal=Phys. Today|year=2012|volume=65|issue=3|pages=46–51|doi=10.1063/PT.3.1477|bibcode = 2012PhT....65c..46M }}

[[Category:Geophysics]]
[[Category:Neutrinos]]

Yen's algorithm - Revision history

en>Monkbot: Fix CS1 deprecated date parameter errors