The Sigma baryons are a family of subatomic hadron particles which have a +2, +1 or −1 elementary charge or are neutral. They are baryons containing three quarks: two up and/or down quarks, and one third quark, which can 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 not expected to be observed as the Standard Model predicts the mean lifetime of top quarks to be roughly 6975500000000000000♠5×10−25 s. This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons.
Contents
List
The symbols encountered in these lists are: I (isospin), J (total angular momentum), P (parity), u (up quark), d (down quark), s (strange quark), c (charm quark), t (top quark), b (bottom quark), Q (charge), S (strangeness), C (charmness), B′ (bottomness), T (topness), as well as other subatomic particles (hover for name).
Antiparticles are not listed in the table; however, they simply would have all quarks changed to antiquarks, and Q, B, S, C, B′, T, would be of opposite signs. I, J, and P values in red have not been firmly established by experiments, but are predicted by the quark model and are consistent with the measurements.
JP = 1/2+ Sigma baryons
† ^ Particle currently unobserved, but predicted by the standard model.
[a] ^ PDG reports the resonance width (Γ). Here the conversion τ = ħ/Γ is given instead.
[b] ^ The specific values of the name has not been decided yet, but will likely be close to
Σ
b(5810).
JP = 3/2+ Sigma baryons
† ^ Particle currently unobserved, but predicted by the standard model.
[c] ^ PDG reports the resonance width (Γ). Here the conversion τ = ħ/Γ is given instead.