Sigma baryon


The Sigma baryons are a family of subatomic hadron particles which have two quarks from the first flavour generation, and a third quark from higher flavour generations, in a combination where the wavefunction does not swap sign 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, a charm, a bottom or a top 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. This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons.

List

The symbols encountered in these lists are: I, J, P, u, d, s, c, t, b, Q, S, C, B′, T, as well as other subatomic particles.
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 = + Sigma baryons

† The standard model predicts that this particle cannot exist due to the short lifetime of the top quark.
PDG reports the resonance width. Here the conversion τ = is given instead.
The specific values of the name has not been decided yet, but will likely be close to.

JP = + Sigma baryons

Particle nameSymbolQuark
content		Rest mass IJPQ SCB'TMean lifetime Commonly decays to
Sigma1,382.8 ± 0.41++1−1000

Sigma1,383.7 ± 1.01+0−1000

Sigma1,387.2 ± 0.51+−1−1000

charmed Sigma2,518.4 ± 0.61 ++20+100
charmed Sigma2,517.5 ± 2.31 ++10+100
charmed Sigma2,518.0 ± 0.51 +00+100
bottom SigmaUnknown1 ++100−10UnknownUnknown
bottom SigmaUnknown1 +000−10UnknownUnknown
bottom SigmaUnknown1 +−100−10UnknownUnknown
Top Sigma—1 ++2000+1——
Top Sigma—1 ++1000+1——
Top Sigma—1 +0000+1——

† The standard model predicts that this particle cannot exist due to the short lifetime of the top quark.
PDG reports the resonance width. Here the conversion τ = is given instead.