Strange particles and strangenessAQA A-Level Physics: Mind map

Exam questions on Strange particles and strangeness

1. In a collision experiment a fast-moving proton collides with a stationary proton, and the reaction p + p → p + p + K⁺ + K⁻ is observed. The strangeness of K⁺ is +1.
   Explain why the K⁺ and K⁻ are produced together in this reaction.2 marks
2. The neutral kaon K⁰ has strangeness +1 and decays into a π⁺ and a π⁻ with a mean lifetime of about 10⁻¹⁰ s. Reactions that produce kaons from collisions between hadrons typically take place in about 10⁻²³ s.
   Suggest why kaons are described as strange particles, using the information given.2 marks
3. Physicists use conservation laws to decide which reactions can occur through the strong interaction. The strangeness of K⁺ and K⁰ is +1 and the strangeness of K⁻ is −1. Protons, neutrons and pions have strangeness 0.
   Determine whether the reaction p + p → p + n + K⁺ can occur through the strong interaction.3 marks