Editing Weakly interacting massive particle (section)

== Indirect detection ==
{{see also|Indirect detection of dark matter}}
Because WIMPs may only interact through gravitational and weak forces, they would be extremely difficult to detect. However, there are many experiments underway to attempt to detect WIMPs both directly and indirectly. ''Indirect detection'' refers to the observation of annihilation or decay products of WIMPs far away from Earth. Indirect detection efforts typically focus on locations where WIMP dark matter is thought to accumulate the most: in the centers of galaxies and galaxy clusters, as well as in the smaller [[Satellite galaxy|satellite galaxies]] of the Milky Way. These are particularly useful since they tend to contain very little baryonic matter, reducing the expected background from standard astrophysical processes. Typical indirect searches look for excess [[gamma rays]], which are predicted both as final-state products of annihilation, or are produced as charged particles interact with ambient radiation via [[inverse Compton scattering]]. The spectrum and intensity of a gamma ray signal depends on the annihilation products, and must be computed on a model-by-model basis. Experiments that have placed bounds on WIMP annihilation, via the non-observation of an annihilation signal, include the [[Fermi Gamma-ray Space Telescope|Fermi]]-LAT gamma ray telescope<ref>{{cite journal |doi=10.1103/PhysRevD.89.042001 |title=Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope |date=2014 |collaboration=The Fermi-LAT Collaboration |journal=Physical Review D |volume=89 |issue=4 |pages=042001 |arxiv=1310.0828 |last1=Ackermann |first1=M. |display-authors=etal |bibcode=2014PhRvD..89d2001A |s2cid=46664722 }}</ref> and the VERITAS ground-based gamma ray observatory.<ref>{{cite journal |last1=Grube |first1=Jeffrey |title=VERITAS Limits on Dark Matter Annihilation from Dwarf Galaxies |pages=689–692 |author2=VERITAS Collaboration |year=2012 |doi=10.1063/1.4772353 |journal=AIP Conference Proceedings|volume=1505 |bibcode=2012AIPC.1505..689G |arxiv = 1210.4961 |s2cid=118510709 }}</ref> Although the annihilation of WIMPs into Standard Model particles also predicts the production of high-energy neutrinos, their interaction rate is thought to be too low to reliably detect a dark matter signal at present. Future observations from the [[IceCube]] observatory in Antarctica may be able to differentiate WIMP-produced neutrinos from standard astrophysical neutrinos; however, by 2014, only 37 cosmological neutrinos had been observed,<ref>{{cite journal |doi=10.1103/PhysRevLett.113.101101 |pmid=25238345 |title=Observation of High-Energy Astrophysical Neutrinos in Three Years of IceCube Data |date=2014 |collaboration=IceCube Collaboration
 |journal=Physical Review Letters |volume=113 |issue=10 |pages=101101 |arxiv=1405.5303 |bibcode=2014PhRvL.113j1101A |last1=Aartsen |first1=M. G. |s2cid=220469354 |display-authors=etal}}</ref> making such a distinction impossible.

Another type of indirect WIMP signal could come from the Sun. Halo WIMPs may, as they pass through the Sun, interact with solar protons, helium nuclei as well as heavier elements. If a WIMP loses enough energy in such an interaction to fall below the local [[escape velocity]], it would theoretically not have enough energy to escape the gravitational pull of the Sun and would remain gravitationally bound.<ref name="Griest" /> As more and more WIMPs thermalize inside the Sun, they would begin to [[annihilation|annihilate]] with each other, theoretically forming a variety of particles, including high-energy [[neutrino]]s.<ref>{{cite journal |doi=10.1103/PhysRevD.74.115007 |title=Indirect detection of light neutralino dark matter in the next-to-minimal supersymmetric standard model |date=2006 |last1=Ferrer |first1=F. |last2=Krauss |first2=L. M. |last3=Profumo |first3=S. |journal=Physical Review D |volume=74 |issue=11 |pages=115007 |arxiv=hep-ph/0609257 |bibcode=2006PhRvD..74k5007F |s2cid=119351935 }}</ref> These neutrinos may then travel to the Earth to be detected in one of the many neutrino telescopes, such as the [[Super-Kamiokande]] detector in Japan. The number of neutrino events detected per day at these detectors depends on the properties of the WIMP, as well as on the mass of the [[Higgs boson]]. Similar experiments are underway to attempt to detect neutrinos from WIMP annihilations within the Earth<ref>{{cite journal |doi=10.1016/0370-2693(86)90349-7|title=Can scalar neutrinos or massive Dirac neutrinos be the missing mass?|journal=Physics Letters B|volume=167|issue=3|pages=295–300|year=1986|last1=Freese|first1=Katherine|bibcode=1986PhLB..167..295F}}</ref> and from within the galactic center.<ref>{{cite journal |doi=10.1142/S0217732305017391 |title=Dark Matter Dynamics and Indirect Detection |date=2005 |last1=Merritt |first1=D. |last2=Bertone |first2=G. |author-link=David Merritt |journal=Modern Physics Letters A |volume=20 |issue=14 |pages=1021–1036 |arxiv=astro-ph/0504422 |bibcode=2005MPLA...20.1021B |s2cid=119405319 }}</ref><ref>{{cite journal |arxiv=astro-ph/0612786 |last1=Fornengo |first1=Nicolao |author-link=Nicolao Fornengo |title=Status and perspectives of indirect and direct dark matter searches |journal=Advances in Space Research |volume=41 |issue=12 |pages=2010–2018 |year=2008 |doi=10.1016/j.asr.2007.02.067|bibcode=2008AdSpR..41.2010F |s2cid=202740 }}</ref>