Why are neutrino/anti-neutrino released in Beta decay? [closed]








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In positive beta decay neutrino are released whereas in negative beta decay anti neutrino are released. From where did they came? Are they produced during the collision? What s it's purpose? Is it to conserve the linear momentum or angular momentum or energy distribution of positrons?




Neutrinos come from the elementary nuclear reactions:
$$n^0\to p^++e^-+\overline\nu$$
or
$$p^+\to n^0+e^++\nu$$
Not sure what do you mean by collision, since beta decay normally does not include any collision (unless there is an electron capture, of course; but neutrino emission occurs anyway, capture or no capture). As for the purpose, they have none, much like other things in nature. Well, by simply being there and having some energy and other things, they somehow participate in conservation of these things. In fact, before the neutrinos were first detected, they brought about a great deal of confusion among physicists by causing an [apparent *violation*](https://en.wikipedia.org/wiki/Beta_decay#Neutrinos) of energy conservation law (which ultimately led to their discovery).


Some might say that neutrino's "purpose" is to conserve the [lepton number](https://en.wikipedia.org/wiki/Lepton_number), but that's a *post factum* explanation.


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