Σ-baryon
|
Sigma baryon (Σ + ) |
|
|---|---|
| classification | |
|
Fermion Hadron Baryon |
|
| properties | |
| electric charge | 1 e (+1.602 10 −19 C ) |
| Resting energy | 1189.37 ± 0.07 MeV |
| magnetic moment | 2.458 ± 0.010 µ N |
| Spin parity | 1/2 + |
| Isospin | 1 (z component +1) |
| Strangeness | −1 |
| average lifespan | (0.8018 ± 0.0026) · 10 −10 s |
|
Quark composition |
uus |
|
Σ 0 |
|
|---|---|
| classification | |
|
Fermion Hadron Baryon |
|
| properties | |
| electric charge | neutral |
| Resting energy | 1192.642 ± 0.024 MeV |
| Spin parity | 1/2 + |
| Isospin | 1 (z component 0) |
| Strangeness | −1 |
| average lifespan | (7.4 ± 0.7) 10 −20 s |
|
Quark composition |
uds |
|
Σ - |
|
|---|---|
| classification | |
|
Fermion Hadron Baryon |
|
| properties | |
| electric charge | −1 e (−1.602 · 10 −19 C ) |
| Resting energy | 1197.449 ± 0.030 MeV |
| magnetic moment | −1.160 ± 0.025 μ N |
| Spin parity | 1/2 + |
| Isospin | 1 (z component −1) |
| Strangeness | −1 |
| average lifespan | (1.479 ± 0.011) · 10 −10 s |
|
Quark composition |
dds |
The three Σ-baryons , also sigma baryons , are baryons that consist of a strange quark and all pair combinations of up and down quarks . They have spin 1/2, isospin 1 and are characterized by their electrical charge : Σ + , Σ 0 and Σ - .
The Σ-baryons belong to the hyperons .
description
The Σ-baryons belong to the SU (3) octet.
Almost 100% of the charged Σ-baryons decay into a nucleon and a pion . Here, the Σ - due to its negative charge only in a neutron and a π - disintegrate, whereas the Σ + with equal probability in a neutron and a π + as a proton and a π 0 decays.
The uncharged Σ 0 decays into a Λ-baryon and a photon with almost 100% probability . This decay takes place by means of the electromagnetic interaction , so that this particle is significantly shorter-lived than the charged Σ-baryons.
Excited states
The Σ baryons have excited states , which as Σ * -Baryonen be called. They have the same quark content as the Σ-baryons, but spin 3/2, and are part of the baryon decuplet. They are slightly heavier than the Σ-baryons (Σ - * ≈ 1387 MeV / c 2 , Σ 0 * ≈ 1384 MeV / c 2 , Σ + * ≈ 1383 MeV / c 2 ).
The Σ * -baryons mostly decay under the strong nuclear force into a pion and a Σ-baryon or into a pion and a Λ-baryon. To a small extent (≈ 1.3%) the Σ 0 * -baryon breaks down into a Λ-baryon and a photon .
See also
Individual evidence
- ↑ a b c d The information on the particle properties (Infobox) are taken from: J. Beringer et al. ( Particle Data Group ): 2013 Review of Particle Physics. In: Physical Review D . Vol. 86, 2012, 010001 and 2013 partial update for the 2014 edition. Particle Data Group, accessed May 23, 2018 .