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Welcome to our Physics lesson on Strangeness, this is the sixth lesson of our suite of physics lessons covering the topic of Particles and Antiparticles - Interaction and Laws of Conservation, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
The experimental data found during the second half of the last century enriched the world of elementary particles with new ones. Some of them didn't need to have known in the explanation of theory the structure of matter and fields or the known interactions involved. For this reason, scientists names these elementary particles "strange". The distinctive feature of such particles is their generation in pairs. For example, Σ-hyperon is produced together with K-mesons (K+, K-, K0) otherwise known as kaons. This generation is pairs is similar to those of electron-antineutrino or positron-neutrino pairs. Like all the other particles that are produced in pairs, the strange particles have a specific charge associated with, the law of conservation of which, allows us to determine whether a specific reaction involving such particles can occur or not. This new type of charge is known as Strangeness, S.
Nucleons, muons and π-mesons do not manifest any strange behavior or property. Therefore their strangeness is S = 0. On the other hand, two strange elementary particles that belong to the same pair have their strangeness equal and opposite. In this way, the algebraic sum of strangeness before and after the reaction takes place must be the same. Thus, the Λ0, Σ+, Σ- and Σ0 hyperons have S = -1 whereas their corresponding accompanying particles K0 and K+ have S = +1. The corresponding antiparticles of elementary particles mentioned above, have an opposite strangeness. Thus, Λ0, Σ+, Σ-, Σ0 have S = +1 while K0 and K- have S = -1.
The law of strangeness conservation is applicable only in strong interaction; it is not applied in weak interaction observed during radioactive decay processes.
Which of the following reactions can occur based on the law of strangeness conservation?
It is clear that the strangeness is not conserved as the values in both sides are different. Hence, this reaction cannot occur.
You have reached the end of Physics lesson 21.2.6 Strangeness. There are 6 lessons in this physics tutorial covering Particles and Antiparticles - Interaction and Laws of Conservation, you can access all the lessons from this tutorial below.
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