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Anti-matter and matter

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
Reply 1
Avatar for TajwarC
TajwarC
17
Yes I believe so. Energy and momentum must be conserved. In order for pair production to happen the gamma ray photon must have enough energy to produce the rest mass of both particles produced, if only one was produced energy wouldn't be conserved
Reply 2
Avatar for EuanF
EuanF
2
Original post by jsmith6131
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


Lepton and baryon numbers must be conserved. If you create a baryon (e.g anti-proton) you have to create an opposite baryon (proton).
Original post by EuanF
Lepton and baryon numbers must be conserved. If you create a baryon (e.g anti-proton) you have to create an opposite baryon (proton).


I am talking about beta decay as an example.
p -> e+ and neutron and neutrino

so I am wondering why the neutrino is NOT an anti particle. I figured it must have to do with an antiparticle law...but no proton is producede
Reply 4
Avatar for EuanF
EuanF
2
Original post by jsmith6131
I am talking about beta decay as an example.
p -> e+ and neutron and neutrino

so I am wondering why the neutrino is NOT an anti particle. I figured it must have to do with an antiparticle law...but no proton is producede


Beta decay emits an electron and antineutrino.

Antineutrino conserves the lepton number.

P(1B) = N(1B) + e(1L) + Antineutrino(-1L)
At the beginning, there is just a proton, so the lepton number is 0. A positron is produced, which is an antilepton, so the lepton number becomes -1. You need a lepton to be produced as well, so that the lepton number becomes 0 overall after the decay, like it was before.
Original post by EuanF
Beta decay emits an electron and antineutrino.

Antineutrino conserves the lepton number.

P(1B) = N(1B) + e(1L) + Antineutrino(-1L)


That's beta minus decay, beta plus decay emits a neutron, positron, and a neutrino
Reply 7
Avatar for EuanF
EuanF
2
Original post by lukethedonkey
That's beta minus decay, beta plus decay emits a neutron, positron, and a neutrino


Ah, thanks

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