Hexaquark

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

In particle physics hexaquarks are a large family of hypothetical particles that would consist of six quarks or antiquarks of any flavours. With six constituent particles, there are several ways to combine quarks so that their colour charge is zero: a hexaquark can either contain six quarks, resembling two baryons bound together (a dibaryon), or three quarks and three antiquarks.^[1] Dibaryons are predicted to be fairly stable once formed. Robert Jaffe proposed the existence of a possibly stable H dibaryon (with the quark composition udsuds), made by combining two uds hyperons, in 1977.^[2]

A number of experiments have been suggested to detect dibaryon decays and interactions. Several candidate dibaryon decays were observed but not confirmed in the 1990s.^[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. Conversely, measurements of neutron stars 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 . These dibaryons would very quickly dissolve into quark–gluon plasma during the collapse, or go into some currently unknown state of matter.

In 2014 a potential dibaryon was detected at the Jülich Research Center at about 2380 MeV. The particle existed for 10⁻²³ seconds and was named d*(2380).^[9]

See also

• Exotic hadron
• Deuteron, the only known stable composite particle that consist of six quarks.
• Diproton, an extremely unstable dibaryon.
• Dineutron, another extremely unstable dibaryon.
• Pentaquark

References

1. Vijande, J.; Valcarce, A; Richard, J.-M. (25 November 2011). "Stability of hexaquarks in the string limit of confinement". arXiv:1111.5921v1.
2. R. L. Jaffe (1977). "Perhaps a Stable Dihyperon?". Physical Review Letters. 38 (5): 195. Bibcode:1977PhRvL..38..195J. doi:10.1103/PhysRevLett.38.195.
3. J. Belz et al. (BNL-E888 Collaboration) (1996). "Search for the weak decay of an H dibaryon". Physical Review Letters. 76: 3277–3280. arXiv:hep-ex/9603002. Bibcode:1996PhRvL..76.3277B. doi:10.1103/PhysRevLett.76.3277.
4. R. W. Stotzer et al. (BNL-E836 Collaboration) (1997). "Search for H dibaryon in He-3 (K-, k+) Hn". Physical Review Letters. 78: 3646–36490. Bibcode:1997PhRvL..78.3646S. doi:10.1103/PhysRevLett.78.3646.
5. A. Alavi-Harati et al. (KTeV Collaboration) (2000). "Search for the weak decay of a lightly bound H0 dibaryon". Physical Review Letters. 84: 2593–2597. arXiv:hep-ex/9910030. Bibcode:2000PhRvL..84.2593A. doi:10.1103/PhysRevLett.84.2593.
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: 1576. arXiv:nucl-th/9706080. Bibcode:1997PhRvC..56.1576F. doi:10.1103/PhysRevC.56.1576.
9. 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.