Hyperon

SU (3) -Baryon octet (spin 1/2) with the quantum numbers isospin I ₃ , strangeness S and electrical charge Q

SU (3) -Baryon decuplet (spin 3/2) with the same quantum numbers. All particles except the Ω-baryon are short-lived (spin) excitations of the ground states in the octet and can decay through the strong interaction .

As hyperons are baryons indicated that at least one strange quark (s-quark), but no heavy quark (thus Charm or bottom quark ) as valence quark included. Hyperons were first detected in the 1950s. They are unstable and, unlike nucleons, do not participate in the structure of normal matter, but belong to the strange particles . Atomic nuclei that contain hyperons are called hyper nuclei .

Nomenclature and properties

The nomenclature of the hyperons depends on the number of their s-quarks, i. H. according to their strangeness :

1 s quark: Lambda (Λ) ( Isospin = 0) and Sigma (Σ) (Isospin = 1)
2 s-quarks: Xi (Ξ)
3 s quarks: Omega (Ω).

Hyperons usually decay under the influence of the weak interaction . A medium-heavy s-quark is converted into a light u- quark , which is conveyed by exchanging a W ^- - . These bosons for their part mostly couple to quarks. B. pions arise ( hadronic decay ), but can also change into leptons ( semileptonic decay ). Since some hyperons decay in violation of parity (e.g. Λ → pπ ^- ), they played an important role in the development of a theory for the weak interaction.

Hyperon	Quark content	Spin and Parity (J ^P )	iso- spin	Strange- ness	Mass ( MeV )	Lifetime (s)	Decay channels
Lambda Λ	uds	1/2 ⁺	0	−1	1115.683 (6)	2.632 (20) · 10 ⁻¹⁰	pπ ^- , nπ ⁰
Sigma Σ ⁺	uus	1/2 ⁺	1	−1	1189.37 (7)	0.8018 (26) · 10 ⁻¹⁰	pπ ⁰ , nπ ⁺
Sigma Σ ⁰	uds	1/2 ⁺	1	−1	1192.642 (24)	7.4 (7) · ^10-20	Λγ
Sigma Σ ^-	dds	1/2 ⁺	1	−1	1197,449 (30)	1.479 (11) · 10 ⁻¹⁰	nπ ^-
Xi Ξ ⁰	uss	1/2 ⁺	1/2	−2	1314.86 (20)	2.90 (9) 10 ⁻¹⁰	Λπ ⁰
Xi Ξ ^-	dss	1/2 ⁺	1/2	−2	1321.71 (7)	1.639 (15) · 10 ⁻¹⁰	Λπ ^-
Sigma Σ ^{* +} (1385)	uus	3/2 ⁺	1	−1	1382.80 (35)		Λπ, Σπ
Sigma Σ ^{* 0} (1385)	uds	3/2 ⁺	1	−1	1383.7 (1.0)		Λπ, Σπ
Sigma Σ ^{* -} (1385)	dds	3/2 ⁺	1	−1	1387.2 (5)		Λπ, Σπ
Xi Ξ ^{* 0} (1530)	uss	3/2 ⁺	1/2	−2	1531.80 (32)		Ξπ
Xi Ξ ^{* -} (1530)	dss	3/2 ⁺	1/2	−2	1535.0 (6)		Ξπ
Omega Ω ^-	sss	3/2 ⁺	0	−3	1672.45 (29)	0.821 (11) · 10 ⁻¹⁰	ΛK ^- , Ξ ⁰ π ^- , Ξ ^- π ⁰

Concept history

The term hyperon originated before the discovery of quarks. A first definition was: A hyperon is a particle that is heavier than the neutron , but lighter than the deuteron . With the introduction of quarks as fundamental particles , the definition was also changed to baryons, which contain s-quarks . With the discovery of the heavy quarks Charm and Bottom, this definition also became imprecise, but not further specified. Instead, a classification scheme for the baryons was designed. The name Hyperon is still used as a collective term in the definition above.

literature

Walter Greiner , Berndt Mueller : Quantum Mechanics. Symmetries. 4th edition. German, Frankfurt am Main 2005, ISBN 3-8171-1616-0 .
Horst Stöcker (Ed.): Pocket book of physics. 5th edition. German, Frankfurt am Main 2005, ISBN 3-8171-1720-5 .
Bogdan Povh , Klaus Rith , Christoph Scholz, Frank Zetsche: Particles and Cores. 8th edition. Springer, Berlin 2009, ISBN 978-3-540-68075-8 .

Web links

Wiktionary: Hyperon - explanations of meanings, word origins, synonyms, translations

Particle Data Group (English)

Individual evidence

^ Walter Greiner, Berndt Mueller: Quantum Mechanics. Symmetries. 3. Edition. German, Frankfurt am Main 1990, ISBN 3-8171-1142-8 . ( Theoretical Physics. Volume 5).
^ TD Lee et al .: Possible Detection of Parity Nonconservation in Hyperon Decay . In: Phys. Rev. , 106, 1957, p. 1367, doi: 10.1103 / PhysRev.106.1367
↑ ^a ^b 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. (No longer available online.) Particle Data Group, archived from the original on February 26, 2014 ; accessed on February 26, 2014 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2
↑ E. Amaldi et al .: Symbols for fundamental particles . In: Nature . tape 173 , 1954, pp. 123 , doi : 10.1038 / 173123a0 .
^ Bogdan Povh , Klaus Rith, Christoph Scholz, Frank Zetsche: Particles and cores. 8th edition. Springer, Berlin 2009, ISBN 978-3-540-68075-8 .
↑ K. Nakamura et al .: Review of Particle Physics . In: J. Phys. G, no. 37 , 2010, Chapter 8 Naming scheme for hadrons , p. 075021 ( pdg.lbl.gov ).

[1] Walter Greiner, Berndt Mueller: Quantum Mechanics. Symmetries. 3. Edition. German, Frankfurt am Main 1990, ISBN 3-8171-1142-8 . ( Theoretical Physics. Volume 5).

[2] TD Lee et al .: Possible Detection of Parity Nonconservation in Hyperon Decay . In: Phys. Rev. , 106, 1957, p. 1367, doi: 10.1103 / PhysRev.106.1367

[PDG-3] 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. (No longer available online.) Particle Data Group, archived from the original on February 26, 2014 ; accessed on February 26, 2014 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2

[4] E. Amaldi et al .: Symbols for fundamental particles . In: Nature . tape 173 , 1954, pp. 123 , doi : 10.1038 / 173123a0 .

[5] Bogdan Povh , Klaus Rith, Christoph Scholz, Frank Zetsche: Particles and cores. 8th edition. Springer, Berlin 2009, ISBN 978-3-540-68075-8 .

[6] K. Nakamura et al .: Review of Particle Physics . In: J. Phys. G, no. 37 , 2010, Chapter 8 Naming scheme for hadrons , p. 075021 ( pdg.lbl.gov ).