In particle physics, the lightest supersymmetric particle (LSP) is the generic name given to the lightest of the additional hypothetical particles found in supersymmetric models. In models with R-parity conservation, the LSP is stable; in other words, it cannot decay into any Standard Model particle, since all SM particles have the opposite R-parity. There is extensive observational evidence for an additional component of the matter density in the universe, which goes under the name dark matter. The LSP of supersymmetric models is a dark matter candidate and is a weakly interacting massive particle (WIMP).[1]
The LSP is unlikely to be a charged wino, charged higgsino, slepton, sneutrino, gluino, squark, or gravitino but is most likely a mixture of neutral higgsinos, the bino and the neutral winos,[2] i.e. a neutralino. In particular, if the LSP were charged (and is abundant in our galaxy) such particles would have been captured by the Earth's magnetic field and form heavy hydrogen-like atoms.[3] Searches for anomalous hydrogen in natural water[4] however have been without any evidence for such particles and thus put severe constraints on the existence of a charged LSP.
As a dark matter candidateedit
Dark matter particles must be electrically neutral; otherwise they would scatter light and thus not be "dark". They must also almost certainly be non-colored.[5] With these constraints, the LSP could be the lightest neutralino, the gravitino, or the lightest sneutrino.
Sneutrino dark matter is ruled out in the Minimal Supersymmetric Standard Model (MSSM) because of the current limits on the interaction cross section of dark matter particles with ordinary matter as measured by direct detection experiments—the sneutrino interacts via Z boson exchange and would have been detected by now if it makes up the dark matter. Extended models with right-handed or sterile sneutrinos reopen the possibility of sneutrino dark matter by lowering the interaction cross section.[6]
Neutralino dark matter is the favored possibility. In most models the lightest neutralino is mostly bino (superpartner of the hyperchargegauge boson field B), with some admixture of neutral wino (superpartner of the weak isospin gauge boson field W0) and/or neutral Higgsino.
Gravitino dark matter is a possibility in supersymmetric models in which the scale of supersymmetry breaking is low, around 100 TeV. In such models the gravitino is very light, of order an eV. As dark matter, the gravitino is sometimes called a super-WIMP because its interaction strength is much weaker than that of other supersymmetric dark matter candidates. For the same reason, its direct thermal production in the early universe is too inefficient to account for the observed dark matter abundance. Rather, gravitinos would have to be produced through the decay of the next-to-lightest supersymmetric particle (NLSP).
In extra-dimensional theories, there are analogous particles called LKPs or Lightest Kaluza–Klein Particle. These are the stable particles of extra-dimensional theories.[7]
^Jungman, Gerard; Kamionkowski, Marc; Griest, Kim (1996). "Supersymmetric dark matter". Phys. Rep. 267 (5–6): 195–373. arXiv:hep-ph/9506380. Bibcode:1996PhR...267..195J. doi:10.1016/0370-1573(95)00058-5. S2CID 119067698.
^Ellis, John R.; Hagelin, J.S.; Nanopoulos, Dimitri V.; Olive, Keith A.; Srednicki, M. (July 1983). "Supersymmetric Relics from the Big Bang". Nucl. Phys. B238 (2): 453–476. Bibcode:1984NuPhB.238..453E. doi:10.1016/0550-3213(84)90461-9. OSTI 1432463.
^Byrne, Mark; Kolda, Christopher; Regan, Peter (2002). "Bounds on Charged, Stable Superpartners from Cosmic Ray Production". Physical Review D. 66 (7): 075007. arXiv:hep-ph/0202252. Bibcode:2002PhRvD..66g5007B. CiteSeerX10.1.1.348.1389. doi:10.1103/PhysRevD.66.075007. S2CID 17073892.
^Smith, P.F.; Bennett, J.R.J.; Homer, G.J.; Lewin, J.D.; Walford, H.E.; Smith, W.A. (November 1981). "A search for anomalous hydrogen in enriched D2O, using a time-of-flight spectrometer". Nucl. Phys. B206 (3): 333–348. Bibcode:1982NuPhB.206..333S. doi:10.1016/0550-3213(82)90271-1.
^McGuire, Patrick C.; Steinhardt, Paul (May 2001). "Cracking open the window for strongly interacting massive particles as the halo dark matter". Proceedings of the 27th International Cosmic Ray Conference. 07-15 August. 4: 1566. arXiv:astro-ph/0105567. Bibcode:2001ICRC....4.1566M.
^Tucker-Smith, David.; Weiner, Neal (February 2004). "The Status of inelastic dark matter". Physical Review D. 72 (6): 063509. arXiv:hep-ph/0402065. Bibcode:2005PhRvD..72f3509T. doi:10.1103/PhysRevD.72.063509. S2CID 115846489.
^Servant, Geraldine.; Tait, Tim M.P. (September 2003). "Is the Lightest Kaluza–Klein Particle a Viable Dark Matter Candidate?". Nuclear Physics B. 650 (1–2): 391–419. arXiv:hep-ph/0206071. Bibcode:2003NuPhB.650..391S. doi:10.1016/S0550-3213(02)01012-X. S2CID 16222693.
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In particle physics the lightest supersymmetric particle LSP is the generic name given to the lightest of the additional hypothetical particles found in supersymmetric models In models with R parity conservation the LSP is stable in other words it cannot decay into any Standard Model particle since all SM particles have the opposite R parity There is extensive observational evidence for an additional component of the matter density in the universe which goes under the name dark matter The LSP of supersymmetric models is a dark matter candidate and is a weakly interacting massive particle WIMP 1 Contents 1 Constraints on LSP from cosmology 2 As a dark matter candidate 3 See also 4 ReferencesConstraints on LSP from cosmology editThe LSP is unlikely to be a charged wino charged higgsino slepton sneutrino gluino squark or gravitino but is most likely a mixture of neutral higgsinos the bino and the neutral winos 2 i e a neutralino In particular if the LSP were charged and is abundant in our galaxy such particles would have been captured by the Earth s magnetic field and form heavy hydrogen like atoms 3 Searches for anomalous hydrogen in natural water 4 however have been without any evidence for such particles and thus put severe constraints on the existence of a charged LSP As a dark matter candidate editDark matter particles must be electrically neutral otherwise they would scatter light and thus not be dark They must also almost certainly be non colored 5 With these constraints the LSP could be the lightest neutralino the gravitino or the lightest sneutrino Sneutrino dark matter is ruled out in the Minimal Supersymmetric Standard Model MSSM because of the current limits on the interaction cross section of dark matter particles with ordinary matter as measured by direct detection experiments the sneutrino interacts via Z boson exchange and would have been detected by now if it makes up the dark matter Extended models with right handed or sterile sneutrinos reopen the possibility of sneutrino dark matter by lowering the interaction cross section 6 Neutralino dark matter is the favored possibility In most models the lightest neutralino is mostly bino superpartner of the hypercharge gauge boson field B with some admixture of neutral wino superpartner of the weak isospin gauge boson field W0 and or neutral Higgsino Gravitino dark matter is a possibility in supersymmetric models in which the scale of supersymmetry breaking is low around 100 TeV In such models the gravitino is very light of order an eV As dark matter the gravitino is sometimes called a super WIMP because its interaction strength is much weaker than that of other supersymmetric dark matter candidates For the same reason its direct thermal production in the early universe is too inefficient to account for the observed dark matter abundance Rather gravitinos would have to be produced through the decay of the next to lightest supersymmetric particle NLSP In extra dimensional theories there are analogous particles called LKPs or Lightest Kaluza Klein Particle These are the stable particles of extra dimensional theories 7 See also editDark matter Darkon unparticle List of hypothetical particles Supersymmetry Weakly interacting slender particleReferences edit Jungman Gerard Kamionkowski Marc Griest Kim 1996 Supersymmetric dark matter Phys Rep 267 5 6 195 373 arXiv hep ph 9506380 Bibcode 1996PhR 267 195J doi 10 1016 0370 1573 95 00058 5 S2CID 119067698 Ellis John R Hagelin J S Nanopoulos Dimitri V Olive Keith A Srednicki M July 1983 Supersymmetric Relics from the Big Bang Nucl Phys B238 2 453 476 Bibcode 1984NuPhB 238 453E doi 10 1016 0550 3213 84 90461 9 OSTI 1432463 Byrne Mark Kolda Christopher Regan Peter 2002 Bounds on Charged Stable Superpartners from Cosmic Ray Production Physical Review D 66 7 075007 arXiv hep ph 0202252 Bibcode 2002PhRvD 66g5007B CiteSeerX 10 1 1 348 1389 doi 10 1103 PhysRevD 66 075007 S2CID 17073892 Smith P F Bennett J R J Homer G J Lewin J D Walford H E Smith W A November 1981 A search for anomalous hydrogen in enriched D2O using a time of flight spectrometer Nucl Phys B206 3 333 348 Bibcode 1982NuPhB 206 333S doi 10 1016 0550 3213 82 90271 1 McGuire Patrick C Steinhardt Paul May 2001 Cracking open the window for strongly interacting massive particles as the halo dark matter Proceedings of the 27th International Cosmic Ray Conference 07 15 August 4 1566 arXiv astro ph 0105567 Bibcode 2001ICRC 4 1566M Tucker Smith David Weiner Neal February 2004 The Status of inelastic dark matter Physical Review D 72 6 063509 arXiv hep ph 0402065 Bibcode 2005PhRvD 72f3509T doi 10 1103 PhysRevD 72 063509 S2CID 115846489 Servant Geraldine Tait Tim M P September 2003 Is the Lightest Kaluza Klein Particle a Viable Dark Matter Candidate Nuclear Physics B 650 1 2 391 419 arXiv hep ph 0206071 Bibcode 2003NuPhB 650 391S doi 10 1016 S0550 3213 02 01012 X S2CID 16222693 nbsp This particle physics related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Lightest supersymmetric particle amp oldid 1188604455, wikipedia, wiki, book, books, library,
