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Particle physics question A2

Here are some facts about the decay of potassium-40

a) the decay constant for beta decay is only 1.7 x 10^-17 s^-1

b) beta particles emerge with a wide range of energies

c) the decay product calcium-40 is stable

Which fact provides the best experimental evidence for the emission of an anti-neutrino in the decay?

the answer is b but i'm not too sure why :s-smilie:

anyone care to explain? thanks :smile:

Reply 1

Cerdic

Original post by Mr Tall

anyone care to explain? thanks :smile:

Well in beta decay whether + or -, an extra particle has to be released to conserve energy and momentum as the beta particle itself doesn't account for it. When there are a wide range of energies it shows that the beta particle and the neutrino have different shares of the energy released with both having different velocities after the reaction.

A normal beta decay (beta -) as this is has to release an anti-neutrino to conserve lepton number. An electron (beta particle) has a lepton number of +1 and an anti-neutrino has a lepton number of -1. We started with a lepton number of 0 and ended with 0