# The antineutrino in Beta decay

I understand the physical changes in beta decay that eventually lead to the virtual particle, a W- boson being formed. However I do not understand the physical changes that take place, which eventually lead to an antineutrino being emitted. What changes take place in the W- boson, that make it decay into an antineutrino and electron?

I would also be glad if someone could explain why the physical changes take place?

Related High Energy, Nuclear, Particle Physics News on Phys.org
Staff Emeritus
2019 Award
I understand the physical changes in beta decay that eventually lead to the virtual particle, a W- boson being formed.
I'm not sure that I understand what you mean. Also, you do understand that "a virtual particle being formed" is sort of a contradiction. The particle is virtual, not real. It's not formed.

I'm not sure that I understand what you mean. Also, you do understand that "a virtual particle being formed" is sort of a contradiction. The particle is virtual, not real. It's not formed.
By this do you mean that the antineutrino isn't really there after beta decay?
If the production of an antineutrino is virtual, then would you be able to explain how?

Simply, I would like to understand why we have an antineutrino involved ,regardless of it being real or virtual.

Thanks for attempting the answer the question.

Staff Emeritus
2019 Award
There is an antineutrino around to conserve spin (and other quantum numbers, like lepton number). If I have the decay $$n \rightarrow p + e^- + \overline{\nu}$$, I have a spin-1/2 object on the left hand side and without the neutrino, I have either a spin-0 or spin-1 ensemble on the right. I also have L = 0 on the left and L = 1 on the right. Finally, the energy spectrum of the electron is characteristic of three-body decays, not two body decays. For all of these reasons, one expects an additional particle produced, the antineutrino.

Of course, today those (anti-)neutrinos have been measured.

There is an antineutrino around to conserve spin (and other quantum numbers, like lepton number). If I have the decay $$n \rightarrow p + e^- + \overline{\nu}$$, I have a spin-1/2 object on the left hand side and without the neutrino, I have either a spin-0 or spin-1 ensemble on the right. I also have L = 0 on the left and L = 1 on the right. Finally, the energy spectrum of the electron is characteristic of three-body decays, not two body decays. For all of these reasons, one expects an additional particle produced, the antineutrino.

Of course, today those (anti-)neutrinos have been measured.
This has made me understand why it is necessary to produce an anti-neutrino in beta decay. So what are the spin and lepton values for the neutrino which help to create a balances on both sides of the decay?