PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
During a core-collapse supernova, enormous numbers of neutrinos, γ photons, and β− electrons are produced in the outer layers of the collapsing star. Astronomers are interested in detecting the first particles that arrive at Earth from such an event.
(1) Using qualitative reasoning about particle interactions with matter, explain why neutrinos escape the stellar material far more readily than either γ photons or β− electrons.
(2) Predict the order in which neutrinos, γ photons, and β− electrons emitted simultaneously at the stellar surface would be detected at Earth. Explain the physical basis for any time differences among their arrivals.
(3) Outline the essential features of a ground-based detector capable of recording supernova neutrinos. In your answer, compare the detector’s design requirements with those of a typical γ-ray telescope.
(4) Provide an example of a β− decay that might occur in supernova nucleosynthesis and show, using conservation of charge, baryon number, and lepton number, that the decay is allowed.