# Antiparticle production rule?

• B
If I produce an anti-particle (e.g: positron) in a reaction MUST I produce a non-anti particle too (e.g: neutrino)...is this a rule?
thanks

Garlic
Gold Member
If I produce an anti-particle (e.g: positron) in a reaction MUST I produce a non-anti particle too (e.g: neutrino)...is this a rule?
thanks
There are some basic rules to see if a reaction is allowed or not.
1] The total charge of a system cannot change, that means (for example) if you are creating an electron (from a neutral particle), you must also create a plus charged particle to equal their charges to zero.
A0 -> B+ + C- [0=1+(-1)]

2] The total lepton number of a system cannot change. Only leptons carry a lepton number other than zero. Electrons, electron neutrinos, muons, muon neutrinos, taus and tau neutrinos have a lepton number of +1, whereas their corresponding antiparticles have -1.
That is the reason why beta decays have neutrinos in them. In beta minus, a neutron (lepton number or in short L =0) is converted into a proton (L=0) and an electron (L=1) that means we need to have a particle that has a -1 lepton number, which is in this case an electron antineutrino.

3] The flavours cannot change, unless it is a weak reaction. Quarks and leptons carry their own flavours (like electronness, muonness (muons), strangeness (strange quarks) etc.) and their corresponding anti particles have also their own flavours, but negative. For example, electrons have electron flavour =+1 and positrons have electron flavour=-1.
This is the reason why the muon decay looks like this;
μ− → e− + anti electron neutrino + muon neutrino
This conserves both charge, lepton number and flavour of each particles.

So, to sum it up, two sides of the reaction equation must be equal in those aspects.

• BobP
There are some basic rules to see if a reaction is allowed or not.
1] The total charge of a system cannot change, that means (for example) if you are creating an electron (from a neutral particle), you must also create a plus charged particle to equal their charges to zero.
A0 -> B+ + C- [0=1+(-1)]

2] The total lepton number of a system cannot change. Only leptons carry a lepton number other than zero. Electrons, electron neutrinos, muons, muon neutrinos, taus and tau neutrinos have a lepton number of +1, whereas their corresponding antiparticles have -1.
That is the reason why beta decays have neutrinos in them. In beta minus, a neutron (lepton number or in short L =0) is converted into a proton (L=0) and an electron (L=1) that means we need to have a particle that has a -1 lepton number, which is in this case an electron antineutrino.

3] The flavours cannot change, unless it is a weak reaction. Quarks and leptons carry their own flavours (like electronness, muonness (muons), strangeness (strange quarks) etc.) and their corresponding anti particles have also their own flavours, but negative. For example, electrons have electron flavour =+1 and positrons have electron flavour=-1.
This is the reason why the muon decay looks like this;
μ− → e− + anti electron neutrino + muon neutrino
This conserves both charge, lepton number and flavour of each particles.

So, to sum it up, two sides of the reaction equation must be equal in those aspects.
Thank you. very detailed answer. very grateful

• Garlic
Garlic
Gold Member
Thank you. very detailed answer. very grateful