IB Physics HL E 3 9 Neutrinos and Antineutrinos Questions

Identify HL neutrinos and antineutrinos in beta decay, using charge, particle type and Feynman-diagram evidence.

Exam points

Analyse Feynman diagrams for beta-plus and beta-minus decay.
Identify electron neutrinos and antineutrinos and explain their production.
Demonstrate lepton-number conservation and energy transfer in beta interactions.

[Maximum number: 1]

Magnesium-27 nuclei $\left({ }_{12}^{27} \mathrm{Mg}\right)$ decay by beta-minus $\left(\beta^{-}\right)$ decay to form nuclei of aluminium-27 (Al).

A Magnesium-27 nucleus can decay by one of two routes:

Route 1: 70\% of the beta particles are emitted with a maximum kinetic energy of 1.76656 MeV , accompanied by a gamma photon of energy 0.84376 MeV .

Route 2: 30 % of the beta particles have a maximum kinetic energy of 1.59587 MeV with a gamma photon of energy 1.01445 MeV .

The final state of the aluminium-27 nucleus is the same for both routes.

Calculate the difference between the magnitudes of the total energy transfers in parts (a) and (b).
(ii) Explain how the difference in part (b)(ii) arises.

$\text { Difference }=2.6175-(1.76656+0.84376)=2.6175-2.61032=0.007195 \text { «MeV» }$

OR

Difference =2.6175-(1.59587+1.01445)=2.61032=0.007195 «MeV»

9.

b

iii

Another particle/«anti» neutrino is emitted «that accounts for this mass / energy»

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IB Physics HL E 3 9 Neutrinos and Antineutrinos Questions question 1