Strange particles and strangenessAQA A-Level Physics: Flashcards
What these 12 flashcards ask
- What is a strange particle?
- What symbol is used for strangeness?
- What is the strangeness of K⁺ and K⁰?
- What is the strangeness of K⁻?
- What is the strangeness of a proton, neutron or pion?
- Why are strange particles always created in pairs?
- In which interaction is strangeness conserved?
- By how much can strangeness change in a weak interaction?
- Why are kaons called strange?
- What is the change in strangeness in K⁰ → π⁺ + π⁻?
- What else is conserved in strong interactions, besides strangeness?
- How do you decide whether a reaction can be strong or must be weak?
Exam questions on Strange particles and strangeness
- 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
- 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
- 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
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).