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 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, a charm, a bottom or a top 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. 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: , , , u, d, s, c, t, b, , , , , , as well as other subatomic particles.Antiparticles are not listed in the table; however, they simply would have all quarks changed to antiquarks, and,,,,,, would be of opposite signs.,, and values in red have not been firmly established by experiments, but are predicted by the quark model and are consistent with the measurements.
= + sigma baryons
† The standard model predicts that this particle cannot exist.PDG reports the resonance width. Here the conversion is given instead.
The specific values of the name has not been decided yet, but will likely be close to.
= + sigma baryons
| Particle name | Symbol | Quark content | Rest mass | Isospin| | JParity | | charge | | strangeness| | charm | | bottomness| | topness| | Mean lifetime | Commonly decays to |
| Sigma | 1,382.8 ± 0.4 | 1 | +1 | −1 | 0 | 0 | 0 | | ||||
| Sigma | 1,383.7 ± 1.0 | 1 | + | 0 | −1 | 0 | 0 | 0 | | |||
| Sigma | 1,387.2 ± 0.5 | 1 | + | −1 | −1 | 0 | 0 | 0 | | |||
| Charmed sigma | 2,518.4 ± 0.6 | 1 | +2 | 0 | +1 | 0 | 0 | |||||
| Charmed sigma | 2,517.5 ± 2.3 | 1 | + | +1 | 0 | +1 | 0 | 0 | ||||
| Charmed sigma | 2,518.0 ± 0.5 | 1 | + | 0 | 0 | +1 | 0 | 0 | ||||
| Bottom sigma | Unknown | 1 | + | +1 | 0 | 0 | −1 | 0 | Unknown | Unknown | ||
| Bottom sigma | Unknown | 1 | + | 0 | 0 | 0 | −1 | 0 | Unknown | Unknown | ||
| Bottom sigma | Unknown | 1 | + | −1 | 0 | 0 | −1 | 0 | Unknown | Unknown | ||
| Top sigma | — | 1 | + | +2 | 0 | 0 | 0 | +1 | — | — | ||
| Top sigma | — | 1 | + | +1 | 0 | 0 | 0 | +1 | — | — | ||
| Top sigma | — | 1 | + | 0 | 0 | 0 | 0 | +1 | — | — |
† The standard model predicts that this particle cannot exist.
PDG reports the resonance width. Here the conversion is given instead.
The following table compares the nearly-identical Lambda and neutral Sigma baryons:
| Particle name | Symbol | Quark content | Rest mass | Isospin| | Total angular momentum quantum number|Parity | | charge | | strangeness| | charm | | bottomness| | topness| | Mean lifetime | Commonly decays to |
| Lambda | 0 | 0 | −1 | 0 | 0 | 0 | ||||||
| Sigma | 1,192.642 ± 0.024 | 1 | 0 | −1 | 0 | 0 | 0 |