Definition of Baryon

Experiments agree that the number of quarks in the universe is a constant and, to be more precise, the number of baryons is a constant (if antimatter is counted as negative); [ref. needed] In technical terms, the total number of baryons seems to be preserved. In the dominant Standard Model of particle physics, the number of baryons can increase to multiples of three due to the action of sphaerons, although this is rare and has not been observed among experiments. Some major unified theories of particle physics also predict that a single proton can decay, changing the number of baryons of one; However, this has not yet been observed experimentally. It is believed that the excess of baryons compared to antibaryons in the current universe is due to the non-preservation of the number of baryons in the very young universe, although this is not well understood. Subscribe to America`s largest dictionary and get thousands of additional definitions and advanced search – ad-free! Baryons are characterized by a number of baryons B of 1. Their antiparticles, called antibaryons, have a baryon number of −1. For example, an atom containing a proton and a neutron (each with a number of baryons of 1) has a number of baryons of 2. In addition to their differences in composition, baryons and mesons can be distinguished from each other by spin: the three quarks that make up a baryon can only produce half-numbered values, while meson spins are always added to integer values. The very existence of baryons is also an important question in cosmology, as it is believed that the Big Bang produced a state with equal amounts of baryons and antibaryons.

The process by which baryons outnumbered their antiparticles is called baryogenesis. Almost all matter that can be encountered or experienced in everyday life is baryonic matter, which contains atoms of any kind and gives them mass property. Non-baryonic matter, as the name suggests, is any type of matter that is not primarily composed of baryons. These could include neutrinos and free electrons, dark matter, supersymmetric particles, axions, and black holes. For baryons, parity is related to orbital angular momentum by relation:[18] Quarks are fermionic particles of spin 1/2 (S = 1/2). Since spin projections vary in steps of 1 (i.e. 1 ħ), a single quark has a spin vector of length 1/2 and two spin projections (Sz = +1/2 and Sz = −1/2). Two quarks can align their spins, in this case the two spin vectors add up to form a vector of length S = 1 and three spin projections (Sz = +1, Sz = 0 and Sz = −1). If two quarks have non-aligned spins, the spin vectors add up to a vector of length S = 0 and have only one spin projection (Sz = 0), and so on. Since baryons consist of three quarks, their spin vectors can add up to form a vector of length S = 3/2 that has four projections of spin (Sz = +3/2, Sz = +1/2, Sz = −1/2 and Sz = −3/2), or a vector of length S = 1/2 with two projections of spin (Sz = +1/2 and Sz = −1/2). [15] Other exotic baryons have been proposed, such as pentaquarks – baryons of four quarks and an antiquark (B = 1/3 + 1/3 + 1/3 + 1/3 − 1/3 = 1),[5][6], but their existence is not generally accepted. The particle physics community as a whole did not consider their likely existence in 2006[7] and in 2008 considered overwhelming evidence against the existence of the reported pentaquarks.

[8] However, in July 2015, the LHCb experiment observed two resonances compatible with pentaquark states in the decay Λ0b → J/ψK−p, with a combined statistical significance of 15σ. [9] [10] each of the elementary particles having a mass equal to or greater than that of a proton and participating in strong interactions; a hadron with a baryon number of +1 In particle physics, a baryon is a type of composite subatomic particle that contains an odd number of valence quarks (at least 3). [1] Baryons belong to the hadron family; Hadrons are made up of quarks. Baryons are also classified as fermions because they have a half-number spin.