Sigma baryon


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 = 12+ Sigma baryons

JP = 12+ 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 12+ +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 12+ 0 −1 0 0 0 7.4 ± 0.7 × 10−20 Λ0
+ γ
Sigma[6] Σ
dds 1,197.449 ± 0.030 1 12+ −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 12 + +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 12 + +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 12 + 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 12 + +1 0 0 −1 0 Unknown Λ0
b
+ π+
(seen)
bottom Sigma Σ0
b
(?[b])
udb Unknown 1 12 + 0 0 0 −1 0 Unknown Unknown
bottom Sigma[8] Σ
b
(?[b])
ddb 5,815.2 ± 2.7 1 12 + −1 0 0 −1 0 Unknown Λ0
b
+ π
(seen)
Top Sigma Σ++
t
uut 1 12 + +2 0 0 0 +1
Top Sigma Σ+
t
udt 1 12 + +1 0 0 0 +1
Top Sigma Σ0
t
ddt 1 12 + 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 = ħΓ 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 = 32+ Sigma baryons

JP = 32+ 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 32+ +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 32+ 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 32+ −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 32 + +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 32 + +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 32 + 0 0 +1 0 0 4.1 ± 0.5 × 10−23[c] Λ+
c
+ π
bottom Sigma Σ∗+
b
uub Unknown 1 32 + +1 0 0 −1 0 Unknown Unknown
bottom Sigma Σ∗0
b
udb Unknown 1 32 + 0 0 0 −1 0 Unknown Unknown
bottom Sigma Σ∗−
b
ddb Unknown 1 32 + −1 0 0 −1 0 Unknown Unknown
Top Sigma Σ∗++
t
uut 1 32 + +2 0 0 0 +1
Top Sigma Σ∗+
t
udt 1 32 + +1 0 0 0 +1
Top Sigma Σ∗0
t
ddt 1 32 + 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 = ħΓ is given instead.

See also

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. ^ a b c C. Amsler et al. (2008): Particle listings – Σ
    c
    (2455)
  8. ^ a b T. Aaltonen et al. (2007a)
  9. ^ a b c C. Amsler et al. (2008): Particle listings – Σ(1385)
  10. ^ a b c C. Amsler et al. (2008): Particle listings – Σ
    c
    (2520)

Bibliography


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