AQA ยท A level Physics

Quark string breaking and hadrons A-level challenge

Can you get 100%? Use a quantum simulation of string breaking to test quark charge, hadron composition and conservation laws.

Read how a quantum computer models string breaking

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Question

8 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

As a quark and antiquark are separated, energy stored in the strong-interaction field can create a new quark-antiquark pair. Explain why creating a pair can conserve both electric charge and baryon number.

[2 marks]

1(b)

Use the charges u = +2/3 e, d = -1/3 e and anti-d = +1/3 e. Determine the electric charge and baryon number of (i) a proton with composition uud and (ii) a positive pion with composition u anti-d.

[4 marks]

1(c)

Explain why producing a new quark-antiquark pair does not create energy from nothing, and why detectors observe new hadrons rather than isolated quarks.

[2 marks]

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