Sigma baryon

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, Σ0c), a bottom (symbols Σ+b, Σ0b, Σ−b) or a top (symbols Σ++t, Σ+t, Σ0t) 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. This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons.