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 s. This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons.