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Pion Plus Decay

Since the charged pions decay into two particles, a muon and a muon neutrino Fractional electric Charge disappeared, why?

The decay proceeds by the weak interaction $W^{+}$ and can be visualized in terms of Feynman diagrams.

my suggestion is that the Fractional electric Charge disappeared because it does not exist at all in the Quarks mechanism.

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Quarks are not directly observed so their fractional charge is more of a theoretical tool (well established though). In practice only pions are observed and they have no fractional charges - exactly like your intuition tells you. If you are consistent thinker you can go even further and question existence of quarks themselfs then you will not have a problem with charge. – Asphir Dom Sep 22 '12 at 15:29
@Asphir Dom this comment must be answer – Neo Sep 22 '12 at 15:35
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No charge disappeared--- you didn't add the fractions correctly--- the sum of the charges is the same before, during, and after. This is a silly question. – Ron Maimon Sep 23 '12 at 6:30
@Ron Maimon phenomenon is the reason that quarks are never directly observed or found in isolation. phenomenon, magic Now, anything, as long as they do not see does not exist that means physics – Neo Sep 23 '12 at 7:44
@muster-mark: It isn't true that the quarks are not directly observed because they have fractional charge, it is a semi-coincidence that the QCD neutral bound states are integer charged--- you could easily make a theory in which this property failed, just add a fractional charged QCD charged scalar field. You can't for quarks because of electroweak interactions, these have an anomaly cancellation constraint that ends up requiring integer charges for the QCD bound states, essentially because instantons allow the proton to decay to leptons, where the charged lepton is a positron. – Ron Maimon Sep 23 '12 at 17:43

1 Answer

up vote 2 down vote accepted

As you say, there exists a Feynman diagram Feynman diagram

for the process, and the real question is: "what happens with the quarks"

The up and antidown quarks manage to "annihilate" into a virtual W+ which decays into the mu+ and nu_mu.

Simple. All annihilations "disappear" some quantum numbers conserving the over all quantities.

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+1: Just to make it absolutely clear to the OP, the +1/3 and +2/3 charges of the u and d(bar) add up to exactly the whole unit charge (+1) of the W+ so no charge disappears. – FrankH Sep 22 '12 at 14:09
@anna v "what happens with the quarks", strong interaction and fractional electric charge – Neo Sep 22 '12 at 14:13
@muster-mark In the instance you have chosen it is a weak interaction. – dmckee♦ Sep 22 '12 at 14:35
quarks have non zero couplings with all four interactions: strong weak electromagnetic and gravitational.The weak is the one responsible for the decays. – anna v Sep 22 '12 at 14:59

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