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hyperon (hīˈpərŏnˌ), class of elementary particles heavier than nucleons (proton and neutron). The nucleons and the hyperons together make up the baryon family of particles.
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A collective name for any baryon with nonzero strangeness number s. The name hyperon has generally been limited to particles which are semistable, that is, which have long lifetimes relative to 10-22 s and which decay by photon emission or through weaker decay interactions. Hyperonic particles which are unstable (that is, with lifetimes shorter than 10-22 s) are commonly referred to as excited hyperons. The known hyperons with spin 1/2 ℏ (where ℏ is Planck's constant divided by 2π) are Λ, Σ-, Σ0, and Σ+ with s = -1, and Ξ- and Ξ0, with s = -2, together with the Ω- particle, which has spin 3/2 ℏ and s = -3. The corresponding antihyperons have baryon number B = -1, opposite strangenesse s, and charge Q; they are all known empirically.

There is no deep distinction between hyperons and excited hyperons, beyond the phenomenological definition above. Indeed, the hyperon Ω(1672)- and the excited hyperons Ξ(1530) and Σ(1385), together with the unstable nucleonic states Δ(1236), are known to form a unitary decuplet of states with spin 3/2 ℏ. See Baryon, Elementary particle, Symmetry laws (physics), Unitary symmetry

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.


(particle physics)
An elementary particle which has baryon number B = + 1, that is, which can be transformed into a nucleon and some number of mesons or lighter particles, and which has nonzero strangeness number.
A hyperon (as in the first definition) which is semistable (the lifetime is much longer than 10-22 second).
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The pp collision at high energy is known to produce $(1405) among other hyperons, as revealed in missing-mass spectra, MM(p[K.sup.+]).
Notice that similar interaction Hamiltonian, but with other coupling constants, describes the neutrino weak interaction of hyperons in NS matter (e.g., [35]).
Experimentally global polarization of hyperons such as [LAMBDA] provides a measure for both the plasma vorticity and the magnetic field.
NOMAD also measured the production of strange resonances and heavier hyperons. This study was of interest to tune the LUND model parameters and for the theoretical interpretation of [LAMBDA] and [bar.[ALPHA]] polarization measurements.
But under such incredible densities, these nuclei might transform further (right): The protons and neutrons could dissolve into a quark soup; the quarks could change and regroup to form particles called hyperons, which contain at least one strange quark; the nuclei could unite in a single quantum state, called a Bose-Einstein condensate; or something else that we haven't imagined could be created.
Hyperons also contain ups and downs, along with a third type called strange.
For kaons and hyperons, however, the strangeness number was not 0 but +1, -1, +2, or -2.
Riska, "The spectrum of the nucleons and the strange hyperons and chiral dynamics," Physics Reports, vol.
The potential depth for hyperons in baryonic matter is fixed as follows.
Sedrakian, "Composition and stability of hybrid stars with hyperons and quark color-superconductivity," Astronomy and Astrophysics, vol.
In Figure 6, we present differential elliptic flows [v.sub.2]([p.sub.T]) of [K.sup.0.sub.S] mesons and A hyperons in Pb-Au collisions at [square root of [sup.s]NN] = 17.3 GeV.
Korpa, "Self-consistent propagation of hyperons and antikaons in nuclear matter based on relativistic chiral SU(3) dynamics," Nuclear Physics A, vol.