Baryons are strongly interacting fermions — that is, they experience the strong nuclear force and are described by Fermi-Dirac statistics, which apply to all particles obeying the Pauli exclusion principle. This is in contrast to the bosons, which do not obey the exclusion principle.
Baryons, along with mesons, are hadrons, meaning they are particles composed of quarks. Quarks have baryon numbers of B = and antiquarks have baryon number of B = −. The term "baryon" usually refer to triquarks—baryons made of three quarks (B = + + = 1), but there are other "exotic" baryons, such as pentaquarks — baryons made of four quarks and one antiquark (B = + + + − = 1), but their existence is not generally accepted. Theoretically, heptaquarks (5 quarks, 2 antiquarks), nonaquarks (6 quarks, 3 antiquarks), etc. could also exist.
Baryons are classified into groups according to their isospin values and quark content. There are six groups of triquarks — nucleon Delta Lambda Sigma Xi and Omega (). The rules for classification are defined by the Particle Data Group. These rules consider the , and quarks to be light and the , , and to be heavy. The rules cover all the particles that can be made from three of each of the six quarks (up, down, strange, charm, bottom, top) — even though baryons made of top quarks are not expected to exist because of the top quark's short lifetime—but not pentaquarks.:
Quarks carry charge, so knowing the charge of a particle indirectly gives the quark content. For example, the rules above say that the contains a bottom and some combination of two up and/or down quarks. A must be one up quark (Q=), one down quark (Q=−), and one bottom quark (Q=−) to have the correct charge (Q=0).
The number of baryons within one group (excluding resonances) is given by the number of isospin projections possible (2 × isospin + 1). For example there are four 's, corresponding to the four isospin projections of the isospin value I = : (Iz = ), (Iz = ), (Iz = −), and (Iz = −). Another example would be the three 's, corresponding to the three isospin projections of the isospin value I = 1: (Iz = 1), (Iz = 0), and (Iz = −1).
The very existence of baryons is also a significant issue in cosmology because we have assumed that the Big Bang produced a state with equal amounts of baryons and anti-baryons. The process by which baryons come to outnumber their antiparticles is called baryogenesis (in contrast to a process by which leptons account for the predominance of matter over antimatter, leptogenesis).
Using extensible informatics to optimize drug discovery: XIS platform connects researchers with meaningful biological and chemical data.
Jul 01, 2003; The seemingly endless quantity of new data being generated by high-density microarrays and other assays is a mixed blessing for...
Xerox Imaging System (XIS) of Peabody, Mass., has added GNP Computers of Pasadena, Calif., and Logos Corp. of Dedham, Mass., to its Strategic Alliance Program, first announced in June. (Mergers/ Acquisitions/ Alliances)
Oct 19, 1992; Xerox Imaging Systems (xis) of Peabody, Mass., has added GNP Computers of Pasadena, Calif., and Logos Corp. of Dedham,...