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.

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]

J^P = ¹⁄₂⁺ Sigma baryons

J^P = ¹⁄₂⁺ Sigma baryons

Particle name	Symbol	Quark content	Rest mass (MeV/c^2)	I	J^P	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 n0 + π+
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).

J^P = ³⁄₂⁺ Sigma baryons

J^P = ³⁄₂⁺ Sigma baryons

Particle name	Symbol	Quark content	Rest mass (MeV/c^2)	I	J^P	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 Σ+ + π0 or Σ0 + π+
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 Σ+ + π− or Σ0 + π0
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 Σ0 + π− or Σ− + π0 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

1. A. Quadt (2006). "Top quark physics at hadron colliders". European Physical Journal C 48 (3): 835–1000. Bibcode:2006EPJC...48..835Q. doi:10.1140/epjc/s2006-02631-6.
2. C. Amsler et al. (2008): Particle summary tables – Baryons
3. J. G. Körner et al. (1994)
4. C. Amsler et al. (2008): Particle listings – Σ+
5. C. Amsler et al. (2008): Particle listings – Σ0
6. C. Amsler et al. (2008): Particle listings – Σ−
7. C. Amsler et al. (2008): Particle listings – Σ
   c(2455)
8. T. Aaltonen et al. (2007a)
9. C. Amsler et al. (2008): Particle listings – Σ(1385)
10. C. Amsler et al. (2008): Particle listings – Σ
    c(2520)

Bibliography

• C. Amsler et al. (Particle Data Group) (2008). "Review of Particle Physics". Physics Letters B 667 (1): 1. Bibcode:2008PhLB..667....1P. doi:10.1016/j.physletb.2008.07.018.
• J. G. Körner, M. Krämer, and D. Pirjol (1994). "Heavy Baryons". Progress in Particle and Nuclear Physics 33: 787–868. arXiv:hep-ph/9406359. Bibcode:1994PrPNP..33..787K. doi:10.1016/0146-6410(94)90053-1.
• T. Aaltonen et al. (CDF Collaboration) (2007a). "First Observation of Heavy Baryons Σ
  b and Σ∗
  b". Physical Review Letters 99 (20): 202001. arXiv:0706.3868. Bibcode:2007PhRvL..99t2001A. doi:10.1103/PhysRevLett.99.202001.