Sigma baryon
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 5×10−25 s.[1] 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), B (baryon number), 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.[2][3]
JP = 1⁄2+ Sigma baryons
| Particle name | Symbol | Quark content |
Rest mass (MeV/c2) | I | JP | Q (e) | S | C | B' | T | Mean lifetime (s) | Commonly decays to |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sigma[4] | Σ+ | uus | 1,189.37 ± 0.07 | 1 | 1⁄2+ | +1 | −1 | 0 | 0 | 0 | 8.018 ± 0.026 × 10−11 | p+ + π0 or |
| Sigma[5] | Σ0 | uds | 1,192.642 ± 0.024 | 1 | 1⁄2+ | 0 | −1 | 0 | 0 | 0 | 7.4 ± 0.7 × 10−20 | Λ0 + γ |
| Sigma[6] | Σ− | dds | 1,197.449 ± 0.030 | 1 | 1⁄2+ | −1 | −1 | 0 | 0 | 0 | 1.479 ± 0.011 × 10−10 | n0 + π− |
| charmed Sigma[7] | Σ++ c(2455) |
uuc | 2,454.02 ± 0.18 | 1 | 1⁄2 + | +2 | 0 | +1 | 0 | 0 | 3.0 ± 0.4 × 10−22[a] | Λ+ c + π+ |
| charmed Sigma[7] | Σ+ c(2455) |
udc | 2,452.9 ± 0.4 | 1 | 1⁄2 + | +1 | 0 | +1 | 0 | 0 | >1.4 × 10−22[a] | Λ+ c + π0 |
| charmed Sigma[7] | Σ0 c(2455) |
ddc | 2,453.76 ± 0.18 | 1 | 1⁄2 + | 0 | 0 | +1 | 0 | 0 | 3.0 ± 0.5 × 10−22[a] | Λ+ c + π− |
| bottom Sigma[8] | Σ+ b(?[b]) |
uub | 5,807.8+3.7 −3.9 |
1 | 1⁄2 + | +1 | 0 | 0 | −1 | 0 | Unknown | Λ0 b + π+ (seen) |
| bottom Sigma† | Σ0 b(?[b]) |
udb | Unknown | 1 | 1⁄2 + | 0 | 0 | 0 | −1 | 0 | Unknown | Unknown |
| bottom Sigma[8] | Σ− b(?[b]) |
ddb | 5,815.2 ± 2.7 | 1 | 1⁄2 + | −1 | 0 | 0 | −1 | 0 | Unknown | Λ0 b + π− (seen) |
| Top Sigma† | Σ++ t |
uut | — | 1 | 1⁄2 + | +2 | 0 | 0 | 0 | +1 | — | — |
| Top Sigma† | Σ+ t |
udt | — | 1 | 1⁄2 + | +1 | 0 | 0 | 0 | +1 | — | — |
| Top Sigma† | Σ0 t |
ddt | — | 1 | 1⁄2 + | 0 | 0 | 0 | 0 | +1 | — | — |
† ^ 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 name | Symbol | Quark content |
Rest mass (MeV/c2) | I | JP | Q (e) | S | C | B' | T | Mean lifetime (s) | Commonly decays to |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sigma[9] | Σ∗+(1385) | uus | 1,382.8 ± 0.4 | 1 | 3⁄2+ | +1 | −1 | 0 | 0 | 0 | 1.84 ± 0.04 × 10−23[c] | Λ0 + π+ or |
| Sigma[9] | Σ∗0(1385) | uds | 1,383.7 ± 1.0 | 1 | 3⁄2+ | 0 | −1 | 0 | 0 | 0 | 1.8 ± 0.3 × 10−23[c] | Λ0 + π0 or |
| Sigma[9] | Σ∗−(1385) | dds | 1,387.2 ± 0.5 | 1 | 3⁄2+ | −1 | −1 | 0 | 0 | 0 | 1.67 ± 0.09 × 10−23[c] | Λ0 + π− or |
| charmed Sigma[10] | Σ∗++ c(2520) |
uuc | 2,518.4 ± 0.6 | 1 | 3⁄2 + | +2 | 0 | +1 | 0 | 0 | 4.4 ± 0.6 × 10−23[c] | Λ+ c + π+ |
| charmed Sigma[10] | Σ∗+ c(2520) |
udc | 2,517.5 ± 2.3 | 1 | 3⁄2 + | +1 | 0 | +1 | 0 | 0 | >3.9 × 10−23[c] | Λ+ c + π0 |
| charmed Sigma[10] | Σ∗0 c(2520) |
ddc | 2,518.0 ± 0.5 | 1 | 3⁄2 + | 0 | 0 | +1 | 0 | 0 | 4.1 ± 0.5 × 10−23[c] | Λ+ c + π− |
| bottom Sigma† | Σ∗+ b |
uub | Unknown | 1 | 3⁄2 + | +1 | 0 | 0 | −1 | 0 | Unknown | Unknown |
| bottom Sigma† | Σ∗0 b |
udb | Unknown | 1 | 3⁄2 + | 0 | 0 | 0 | −1 | 0 | Unknown | Unknown |
| bottom Sigma† | Σ∗− b |
ddb | Unknown | 1 | 3⁄2 + | −1 | 0 | 0 | −1 | 0 | Unknown | Unknown |
| Top Sigma† | Σ∗++ t |
uut | — | 1 | 3⁄2 + | +2 | 0 | 0 | 0 | +1 | — | — |
| Top Sigma† | Σ∗+ t |
udt | — | 1 | 3⁄2 + | +1 | 0 | 0 | 0 | +1 | — | — |
| Top Sigma† | Σ∗0 t |
ddt | — | 1 | 3⁄2 + | 0 | 0 | 0 | 0 | +1 | — | — |
† ^ 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.
See also
- Delta baryon
- Hyperon
- Lambda baryon
- List of mesons
- List of particles
- Nucleon
- Omega baryon
- Physics portal
- Timeline of particle discoveries
- Xi baryon
References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ C. Amsler et al. (2008): Particle summary tables – Baryons
- ↑ J. G. Körner et al. (1994)
- ↑ C. Amsler et al. (2008): Particle listings – Σ+
- ↑ C. Amsler et al. (2008): Particle listings – Σ0
- ↑ C. Amsler et al. (2008): Particle listings – Σ−
- ↑ 7.0 7.1 7.2 C. Amsler et al. (2008): Particle listings – Σ
c(2455) - ↑ 8.0 8.1 T. Aaltonen et al. (2007a)
- ↑ 9.0 9.1 9.2 C. Amsler et al. (2008): Particle listings – Σ(1385)
- ↑ 10.0 10.1 10.2 C. Amsler et al. (2008): Particle listings – Σ
c(2520)
Bibliography
- Lua error in package.lua at line 80: module 'strict' not found.
- Lua error in package.lua at line 80: module 'strict' not found.
- Lua error in package.lua at line 80: module 'strict' not found.
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