Sigma baryon

Sigma baryon
Composition

  • Σ+
    :
    u

    u

    s

  • Σ0
    :
    u

    d

    s

  • Σ−
    :
    d

    d

    s
StatisticsFermionic
FamilyBaryons
InteractionsStrong, weak, electromagnetic, and gravity
Types3
Mass

  • Σ+
    : 1189.37±0.07 MeV/c2[1]

  • Σ0
    : 1192.642±0.024 MeV/c2

  • Σ−
    : 1197.449±0.030 MeV/c2
Spin1⁄2
Strangeness-1
Isospin1

The sigma baryons are a family of subatomic hadron particles which have two quarks from the first flavour generation (up and / or down quarks), and a third quark from a higher flavour generation, in a combination where the wavefunction sign remains constant when any two quark flavours are swapped. They are thus baryons, with total isospin of 1, and can either be neutral or have an elementary charge of +2, +1, 0, or −1. They are closely related to the lambda baryons, which differ only in the wavefunction's behaviour upon flavour exchange.

The third quark can hence be either a strange (symbols
Σ+
,
Σ0
,
Σ−
), a charm (symbols
Σ++
c,
Σ+
c,
Σ0
c), a bottom (symbols
Σ+
b,
Σ0
b,
Σ−
b) or a top (symbols
Σ++
t,
Σ+
t,
Σ0
t) quark. However, the top sigmas are expected to never be observed, since the Standard Model predicts the mean lifetime of top quarks to be roughly 5×10−25 s.[2] This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons.

  1. ^ Zyla, P. A.; et al. (Particle Data Group) (2020). "Review of Particle Physics". Progress of Theoretical and Experimental Physics. 2020 (8): 083C01. Bibcode:2020PTEP.2020h3C01P. doi:10.1093/ptep/ptaa104. hdl:10261/239127.
  2. ^ Quadt, A. (2006). "Top quark physics at hadron colliders" (PDF). European Physical Journal C. 48 (3): 835–1000. Bibcode:2006EPJC...48..835Q. doi:10.1140/epjc/s2006-02631-6. S2CID 121887478.