Quarks and antiquarksAQA A-Level Physics: Mind map

Exam questions on Quarks and antiquarks

1. A student is learning how hadrons are built from quarks. The only quarks she needs are the up (u), down (d) and strange (s) quarks and their antiquarks.
   The π⁺ meson is made of an up quark and an anti-down quark. Show that its charge is +1 and that its baryon number is 0.2 marks
2. At an accelerator, beams of antiprotons and kaons are produced, and the physicists need to identify the quark structure of the particles they detect.
   The K⁻ is the antiparticle of the K⁺, which is made of an up quark and a strange antiquark. Deduce the quark composition of the K⁻ and show that its strangeness is −1.2 marks
3. A free neutron decays through the weak interaction: n → p + e⁻ + $\bar{\nu}_e$. At the quark level, one quark in the neutron changes into a different quark.
   Identify the change that happens to a quark in the neutron, name the interaction responsible, and show that charge is conserved at the quark level.3 marks