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Hexaquark

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File:H dibaryon.jpg
A dibaryon-type hexaquark. There are two constituent quarks for each of the three colour charges.

In particle physics hexaquarks, alternatively known as sexaquarks[1], are a large family of hypothetical particles, each particle consisting of six quarks or antiquarks of any flavours. Six constituent quarks in any of several combinations could yield a colour charge of zero; for example a hexaquark might contain either six quarks, resembling two baryons bound together (a dibaryon), or three quarks and three antiquarks.[2] Once formed, dibaryons are predicted to be fairly stable by the standards of particle physics.

A number of experiments have been suggested to detect dibaryon decays and interactions. In the 1990s several candidate dibaryon decays were observed but they were not confirmed.[3][4][5]

There is a theory that strange particles such as hyperons[6] and dibaryons[7] could form in the interior of a neutron star, changing its mass–radius ratio in ways that might be detectable. Accordingly, measurements of neutron stars could set constraints on possible dibaryon properties.[8] A large fraction of the neutrons in a neutron star could turn into hyperons and merge into dibaryons during the early part of its collapse into a black hole [citation needed]. These dibaryons would very quickly dissolve into quark–gluon plasma during the collapse, or go into some currently unknown state of matter.

D-star hexaquark

In 2014 a potential dibaryon was detected at the Jülich Research Center at about 2380 MeV. The center claimed that the measurements confirm results from 2011, via a more replicable method.[9][10] The particle existed for 10−23 seconds and was named d*(2380).[11] This particle is hypothesized to consist of three up and three down quarks, and has been proposed as a candidate for dark matter.[12][13][14]

It is theorized that, groups of d-stars could form substances known as Bose-Einstein Condensates —due to prevailing low temperatures in the early universe — a state in which they overlap and blend together, a bit like the protons and neutrons inside atoms. Under the right conditions, BECs made of hexaquarks with trapped electrons could behave like dark matter.[15] As per researchers, this result indicates that during the earliest moments after the Big Bang, as the cosmos slowly cooled, stable d*(2830) hexaquarks could have formed alongside baryonic matter, and the production rate of this particle would have been sufficient to account for the 85% of the Universe’s mass that is believed to be Dark Matter.[16]

H di-baryon

In 1977 Robert Jaffe proposed that a possibly stable H dibaryon with the quark composition udsuds could notionally result from the combination of two uds hyperons.[17] Calculations have shown that this particle is light and (meta)stable. It actually takes more than twice the age of the universe to decay. Data constrains the existence of such a particle, and it turns out that it is still allowed.[18][19][1][20][21][22][23] As per one analysis, a hypothetical SU(3) flavor-singlet, highly symmetric, deeply bound neutral scalar hexaquark S=uuddss, which due to its features has escaped from experimental detection so far, may be considered as a candidate for a baryonic dark matter, but, existence of this state may contradict to stability of the oxygen nuclei, which requires further thorough analysis.[24]

See also

References

  1. ^ a b "Oddball sexaquark particles could be immortal, if they exist at all".
  2. ^ Vijande, J.; Valcarce, A; Richard, J.-M. (25 November 2011). "Stability of hexaquarks in the string limit of confinement". Physical Review D. 85 (1): 014019. arXiv:1111.5921. Bibcode:2012PhRvD..85a4019V. doi:10.1103/PhysRevD.85.014019.
  3. ^ J. Belz et al. (BNL-E888 Collaboration) (1996). "Search for the weak decay of an H dibaryon". Physical Review Letters. 76 (18): 3277–3280. arXiv:hep-ex/9603002. Bibcode:1996PhRvL..76.3277B. doi:10.1103/PhysRevLett.76.3277. PMID 10060926.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  4. ^ R. W. Stotzer et al. (BNL-E836 Collaboration) (1997). "Search for H dibaryon in He-3 (K-, k+) Hn". Physical Review Letters. 78 (19): 3646–36490. Bibcode:1997PhRvL..78.3646S. doi:10.1103/PhysRevLett.78.3646.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  5. ^ A. Alavi-Harati et al. (KTeV Collaboration) (2000). "Search for the weak decay of a lightly bound H0 dibaryon". Physical Review Letters. 84 (12): 2593–2597. arXiv:hep-ex/9910030. Bibcode:2000PhRvL..84.2593A. doi:10.1103/PhysRevLett.84.2593. PMID 11017277.
  6. ^ V. A. Ambartsumyan; G. S. Saakyan (1960). "The Degenerate Superdense Gas of Elementary Particles". Soviet Astronomy. 37: 193. Bibcode:1960SvA.....4..187A.
  7. ^ S. Kagiyama; A. Nakamura; T. Omodaka (1992). "Compressible bag model and dibaryon stars". Zeitschrift für Physik C. 56 (4): 557–560. Bibcode:1992ZPhyC..56..557K. doi:10.1007/BF01474728.
  8. ^ A. Faessler; A. J. Buchmann; M. I. Krivoruchenko (1997). "Constraints to coupling constants of the ω- and σ-mesons with dibaryons". Physical Review C. 56 (3): 1576–1581. arXiv:nucl-th/9706080. Bibcode:1997PhRvC..56.1576F. doi:10.1103/PhysRevC.56.1576.
  9. ^ "Forschungszentrum Jülich press release".
  10. ^ "Massive news in the micro-world: a hexaquark particle".
  11. ^ P. Adlarson; et al. (2014). "Evidence for a New Resonance from Polarized Neutron-Proton Scattering". Physical Review Letters. 112 (2): 202301. arXiv:1402.6844. Bibcode:2014PhRvL.112t2301A. doi:10.1103/PhysRevLett.112.202301.
  12. ^ M. Bashkanov (2020). "A new possibility for light-quark dark matter". Journal of Physics G. 47 (3).
  13. ^ "Physicists Think We Might Have a New, Exciting Dark Matter Candidate".
  14. ^ "Did this newfound particle form the universe's dark matter?".
  15. ^ "Did German physicists accidentally discover dark matter in 2014?".
  16. ^ "Is the "D-star Hexaquark" the Dark Matter Particle?".
  17. ^ R. L. Jaffe (1977). "Perhaps a Stable Dihyperon?". Physical Review Letters. 38 (5): 195–198. Bibcode:1977PhRvL..38..195J. doi:10.1103/PhysRevLett.38.195.
  18. ^ "The mysteries of quantum chromodynamics: from quarks to the sexy sexaquark".
  19. ^ "Stable Sexaquark".
  20. ^ "Dibaryons cannot be the dark matter".
  21. ^ "Dark matter in the standard model?".
  22. ^ "A Stable H-Dibaryon: Dark Matter, Candidate Within QCD?".
  23. ^ "Stable Sexaquark: Dark Matter predictions, constraints and lab detection" (PDF).
  24. ^ "The Scalar Hexaquark uuddss: a Candidate to Dark Matter?".
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