Feynmann diagram for beta decay, direction of arrows confusion

UniPhysics90
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For beta minus decay, I know the reaction is given by neutron -> proton+electron+anti(electron)neutrino.

This is an image of the Feynman diagram for the reaction:

[URL]http://tmp.kiwix.org:4201/I/280px_Beta_Negative_Decay_svg.png[/URL]

I get that the neutron changes to a proton releasing a w- boson. I think this decays into the electron and anti neutrino. Why then in this diagram is the direction of the arrow of the antineutrino 'backwards' so going back in time?

Thanks
 
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UniPhysics90 said:
I get that the neutron changes to a proton releasing a w- boson. I think this decays into the electron and anti neutrino. Why then in this diagram is the direction of the arrow of the antineutrino 'backwards' so going back in time?

Thanks

It's just a convention due to Feynman. Particles are drawn with forward arrows, while antiparticles are drawn with backward arrows. The physical motivation for this is that the antiparticle can be obtain by acting on the particle with the CPT operator. So in a sense, the antiparticle is a particle "traveling backwards in time".
 
fzero said:
It's just a convention due to Feynman. Particles are drawn with forward arrows, while antiparticles are drawn with backward arrows. The physical motivation for this is that the antiparticle can be obtain by acting on the particle with the CPT operator. So in a sense, the antiparticle is a particle "traveling backwards in time".

Thanks, if it's just a convention, I'm happy enough with what it shows :)
 

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