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{{About|a concept in particle physics|the definition of "strangeness"|wikt:strangeness|other uses|Strange (disambiguation)}} | |||
{{No footnotes|date=July 2010}} | |||
{{Flavour_quantum_numbers}} | |||
In [[particle physics]], '''strangeness''' ''S'' is a [[physical property|property]] of particles, expressed as a [[quantum number]], for describing [[particle decay|decay]] of particles in [[strong interaction|strong]] and [[electromagnetic interaction|electromagnetic]] reactions, which occur in a short period of [[time]]. The strangeness of a particle is defined as: | |||
:<math>S = -(n_s - n_{\overline{s}})</math> | |||
where ''n''<sub>{{SubatomicParticle|Strange quark}}</sub> represents the number of [[strange quark]]s ({{SubatomicParticle|Strange quark}}) and ''n''<sub>{{SubatomicParticle|Strange antiquark}}</sub> represents the number of strange antiquarks ({{SubatomicParticle|Strange antiquark}}). | |||
The terms ''strange'' and ''strangeness'' predate the discovery of the quark, and were adopted after its discovery in order to preserve the continuity of the phrase; strangeness of anti-particles being referred to as +1, and particles as −1 as per the original definition. For all the quark flavor quantum numbers (strangeness, [[charm (quantum number)|charm]], [[topness]] and [[bottomness]]) the convention is that the flavor charge and the electric charge of a quark have the same sign. With this, any flavor carried by a charged [[meson]] has the same sign as its charge. | |||
==Strangeness conservation== | |||
Strangeness was introduced by [[Murray Gell-Mann]] and [[Kazuhiko Nishijima]] to explain the fact that certain particles, such as the [[kaon]]s or certain [[hyperon]]s, were created easily in particle collisions, yet decayed much more slowly than expected for their large masses and large production [[cross section (physics)|cross section]]s. Noting that collisions seemed to always produce pairs of these particles, it was postulated that a new conserved quantity, dubbed "strangeness", was preserved during their creation, but ''not'' conserved in their decay. | |||
In our modern understanding, strangeness is conserved during the [[strong interaction|strong]] and the [[electromagnetic interaction]]s, but not during the [[weak interaction]]s. Consequently, the lightest particles containing a strange quark cannot decay by the strong interaction, and must instead decay via the much slower weak interaction. In most cases these decays change the value of the strangeness by one unit. However, this doesn't necessarily hold in second-order weak reactions, where there are mixes of {{SubatomicParticle|Kaon0}} and {{SubatomicParticle|Antikaon0}} mesons. All in all, the amount of strangeness can change in a weak interaction reaction by +1,0 or -1 (depending on the reaction of course). | |||
==See also== | |||
* [[Isospin]] | |||
* [[Charm (quantum number)|Charm]] | |||
* [[Topness]] | |||
* [[Bottomness]] | |||
* [[Hypercharge]] | |||
* [[Strangeness production]] | |||
== References == | |||
*{{cite book | |||
| author=D.J. Griffiths | |||
| year=1987 | |||
| title=Introduction to Elementary Particles | |||
| url=http://books.google.com/books?id=iNjOAQAACAAJ&dq=Introduction+to+Elementary+Particles | |||
| publisher=[[John Wiley & Sons]] | |||
| isbn=0-471-60386-4 | |||
}} | |||
==Further reading== | |||
* [http://arxiv.org/PS_cache/arxiv/pdf/0906/0906.1271v2.pdf Lessons in Particle Physics] Luis Anchordoqui and Francis Halzen, University of Wisconsin, 18th Dec. 2009 | |||
[[Category:Concepts in physics]] | |||
[[Category:Particle physics]] | |||
[[Category:Quarks]] | |||
[[Category:Particle physics flavour quantum number]] | |||
Revision as of 10:52, 23 January 2014
29 yr old Orthopaedic Surgeon Grippo from Saint-Paul, spends time with interests including model railways, top property developers in singapore developers in singapore and dolls. Finished a cruise ship experience that included passing by Runic Stones and Church. Template:No footnotes 51 years old Sportspersons Rusty from Wrigley, spends time with pastimes which includes beach, property agent in singapore developers in singapore and surf fishing. Continues to be inspired how enormous the earth is after making vacation to Saloum Delta.
In particle physics, strangeness S is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic reactions, which occur in a short period of time. The strangeness of a particle is defined as:
where nTemplate:SubatomicParticle represents the number of strange quarks (Template:SubatomicParticle) and nTemplate:SubatomicParticle represents the number of strange antiquarks (Template:SubatomicParticle).
The terms strange and strangeness predate the discovery of the quark, and were adopted after its discovery in order to preserve the continuity of the phrase; strangeness of anti-particles being referred to as +1, and particles as −1 as per the original definition. For all the quark flavor quantum numbers (strangeness, charm, topness and bottomness) the convention is that the flavor charge and the electric charge of a quark have the same sign. With this, any flavor carried by a charged meson has the same sign as its charge.
Strangeness conservation
Strangeness was introduced by Murray Gell-Mann and Kazuhiko Nishijima to explain the fact that certain particles, such as the kaons or certain hyperons, were created easily in particle collisions, yet decayed much more slowly than expected for their large masses and large production cross sections. Noting that collisions seemed to always produce pairs of these particles, it was postulated that a new conserved quantity, dubbed "strangeness", was preserved during their creation, but not conserved in their decay.
In our modern understanding, strangeness is conserved during the strong and the electromagnetic interactions, but not during the weak interactions. Consequently, the lightest particles containing a strange quark cannot decay by the strong interaction, and must instead decay via the much slower weak interaction. In most cases these decays change the value of the strangeness by one unit. However, this doesn't necessarily hold in second-order weak reactions, where there are mixes of Template:SubatomicParticle and Template:SubatomicParticle mesons. All in all, the amount of strangeness can change in a weak interaction reaction by +1,0 or -1 (depending on the reaction of course).
See also
References
- 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
Further reading
- Lessons in Particle Physics Luis Anchordoqui and Francis Halzen, University of Wisconsin, 18th Dec. 2009