While solving numericals from the Concept of Physics by HC Verma , I noticed that he never mentioned the term kinetic energy of a neutrino. There were some questions asking about the maximum kinetic energy possessed by the beta particles in a beta emission and there were others where we were asked to find energy of a neutrino if the kinetic energy of the beta particle was given and the daughter nuclei was assumed to be at rest.

I don't know if there is something relevant here but I don't know why he didn't mention the term Kinetic energy of a neutron.

Isn't it "emitted" in a beta decay process like the beta particles ? More specifically, in which form does that energy appear ?


1 Answer 1


There is a problem answering your question - the neutrino's mass, which is not known. This means that what kinetic energy it has is difficult to say. For a long time neutrinos were thought to be massless

Kinetic energy is defined as energy beyond rest mass due to motion, so using :

$$E^2 = p^2c^2 + m^2c^4$$


$$E_{kinetic} = E - mc^2$$

You see that whether a particle has mass and what that rest mass is changes the kinetic energy you can attribute to it for given momentum and energy values.

The problem is that as we do not know that mass (or masses as there could be multiple "flavors" of each neutrino with different masses for each flavor), we cannot effectively break the energy down into kinetic and rest mass without picking a theory as a basis, something your book won't want to get into and some of which would not have been known when it was printed (1999 ?).

So when textbooks talk about neutrinos in Beta decay they are limited by not being able to make definitive statements. They can stil talk about momentum and energy conservation as that is not affected, but kinetic energy is a problem.


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