In short: charge is not the only thing that defines a particle.
Although the charge of the neutrinos is zero their spin differs.
A longer form of this answer is here. The answers go a bit more into detail on why “zero charge” isn’t precisely correct either but I’m not sure if that goes too deep for what you’re interested in!
On further thought, this is really strange.
I can visualize a negatively charged electron and a positively charged positron making contact and annihilating, how the minus and the plus cancel each other.
But what is it about neutrinos and antineutrinos that make them cancel out when they come into contact? What is it about their positive and negative characteristics that can make them go “poof!” in a burst of photons?
A visualization you could try (this obviously isn’t going to match the physical reality necessarily) is what would happen if you had two vortex phenomena (like tornadoes or whirlpools) spinning in opposite directions and they collided?
I’m going to copy-paste the exact relevant bit here:
For each neutrino, there also exists a corresponding antiparticle, called an antineutrino, which also has no electric charge and half-integer spin. They are distinguished from the neutrinos by having opposite signs of lepton number and chirality. As of 2016, no evidence has been found for any other difference.
I knew about the chirality difference, that there are no right-handed neutrinos nor left-handed antineutrinos (or something along those lines, breaking what was thought to be a fundamental parity or symmetry), but what puzzled me was that I thought the charge difference was the one big fundamental difference between matter and antimatter, and suddenly tonight the neutrino question popped into my head. At the very least I knew that it’s not a mass/negative mass type of difference.
Now as for that bit that says “opposite signs of lepton number”… I’d never even heard of this concept or characteristic, until right now.
Lepton number is an observationally conserved quantity. As far as I know there’s no fundamental reason for it to be conserved (and indeed there are searches for physics beyond the standard model that would violate it) but it’s been found to generally be conserved in reactions so far. Lepton particles have a lepton number of +1, lepton antiparticles have -1.
There’s a similar conserved quantity known as the baryon number, with a similar definition. Protons and neutrons (baryons) have values of +1, anti-protons and anti-neutrons are -1.
An example: consider the beta- decay of a neutron, baryon number +1 and lepton number 0. It emits a proton (baryon number +1), an electron (lepton +1), and an electron anti-neutrino (lepton -1). Total lepton number of the decay products is 1-1=0, so the value is conserved.
In short: charge is not the only thing that defines a particle. Although the charge of the neutrinos is zero their spin differs.
A longer form of this answer is here. The answers go a bit more into detail on why “zero charge” isn’t precisely correct either but I’m not sure if that goes too deep for what you’re interested in!
https://physics.stackexchange.com/questions/338917/what-is-the-difference-between-a-neutrino-and-an-antineutrino#338924
On further thought, this is really strange.
I can visualize a negatively charged electron and a positively charged positron making contact and annihilating, how the minus and the plus cancel each other.
But what is it about neutrinos and antineutrinos that make them cancel out when they come into contact? What is it about their positive and negative characteristics that can make them go “poof!” in a burst of photons?
A visualization you could try (this obviously isn’t going to match the physical reality necessarily) is what would happen if you had two vortex phenomena (like tornadoes or whirlpools) spinning in opposite directions and they collided?
I’m going to copy-paste the exact relevant bit here:
I knew about the chirality difference, that there are no right-handed neutrinos nor left-handed antineutrinos (or something along those lines, breaking what was thought to be a fundamental parity or symmetry), but what puzzled me was that I thought the charge difference was the one big fundamental difference between matter and antimatter, and suddenly tonight the neutrino question popped into my head. At the very least I knew that it’s not a mass/negative mass type of difference.
Now as for that bit that says “opposite signs of lepton number”… I’d never even heard of this concept or characteristic, until right now.
Lepton number is an observationally conserved quantity. As far as I know there’s no fundamental reason for it to be conserved (and indeed there are searches for physics beyond the standard model that would violate it) but it’s been found to generally be conserved in reactions so far. Lepton particles have a lepton number of +1, lepton antiparticles have -1.
There’s a similar conserved quantity known as the baryon number, with a similar definition. Protons and neutrons (baryons) have values of +1, anti-protons and anti-neutrons are -1.
An example: consider the beta- decay of a neutron, baryon number +1 and lepton number 0. It emits a proton (baryon number +1), an electron (lepton +1), and an electron anti-neutrino (lepton -1). Total lepton number of the decay products is 1-1=0, so the value is conserved.