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 . 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]

The study found that production of stable d*(2830) hexaquarks could account for 85% of the Universe's dark matter.^[15][16]

H dibaryon

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][1][18][19][20][21][22][23]}

Others

• In 2022 Riken researchers studied the existence of triply charmed dibaryon ${\displaystyle \Omega _{ccc}\Omega _{ccc}}$ concluding computationally that it should fall within a feasible regime.^[24][25]

See also

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

References