Xi baryon

Xi baryon
Composition

  • Ξ0
    :
    u

    s

    s

  • Ξ−
    :
    d

    s

    s
StatisticsFermionic
FamilyBaryons
InteractionsStrong, weak, electromagnetic, and gravity
Types2
Mass

  • Ξ0
    : 1314.86±0.20 MeV/c2[1]

  • Ξ−
    : 1321.71±0.07 MeV/c2
Spin1⁄2
Strangeness-2
Isospin1⁄2

The Xi baryons or cascade particles are a family of subatomic hadron particles which have the symbol Ξ and may have an electric charge (Q) of +2 e, +1 e, 0, or −1 e, where e is the elementary charge.

Like all conventional baryons, Ξ particles contain three quarks. Ξ baryons, in particular, contain either one up or one down quark and two other, more massive quarks. The two more massive quarks are any two of strange, charm, or bottom (doubles allowed). For notation, the assumption is that the two heavy quarks in the Ξ are both strange; subscripts "c" and "b" are added for each even heavier charm or bottom quark that replaces one of the two presumed strange quarks.

They are historically called the cascade particles because of their unstable state; they are typically observed to decay rapidly into lighter particles, through a chain of decays (cascading decays).[2] The first discovery of a charged Xi baryon was in cosmic ray experiments by the Manchester group in 1952.[3] The first discovery of the neutral Xi particle was at Lawrence Berkeley Laboratory in 1959.[4] It was also observed as a daughter product from the decay of the omega baryon (
Ω−
) observed at Brookhaven National Laboratory in 1964.[2] The Xi spectrum is important to nonperturbative quantum chromodynamics (QCD), such as lattice QCD.[why?]

  1. ^ Zyla, P. A.; et al. (Particle Data Group) (2020). "Review of Particle Physics". Progress of Theoretical and Experimental Physics. 2020 (8): 083C01. doi:10.1093/ptep/ptaa104. hdl:11585/772320.
  2. ^ a b Nave, R. "The Xi Baryon". HyperPhysics. Retrieved 4 April 2013.
  3. ^ Armenteros, R.; et al. (Manchester group) (1952). "The properties of charged V-particles". Philosophical Magazine. 43 (341): 597. doi:10.1080/14786440608520216.
  4. ^ Alvarez, L.W.; et al. (1959). "Neutral Cascade Hyperon Event". Physical Review Letters. 2 (5): 215. Bibcode:1959PhRvL...2..215A. doi:10.1103/PhysRevLett.2.215.