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GATE 2023 PH – Question 48

Nuclear and Particle Physics · photons, baryons, mesons and leptons · 2 marks · Multiple choice

In a hadronic interaction, π0’s are produced with different momenta, and they immediately decay into two photons with an opening angle θ between them. Assuming that all these decays occur in one plane, which one of the following figures depicts the behaviour of θ as a function of the π0 momentum p?

Candidate opening-angle versus pion-momentum graphs.
  1. Option A in the figure
  2. Option B in the figure
  3. Option C in the figure
  4. Option D in the figure

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Show answer and explanation

Correct answer: (A) Option A in the figure

Explanation

At rest the two photons are back-to-back. A boost collimates them so the typical opening angle decreases with pion momentum.