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# What does the neutral pion look like? watch

1. Right, so I imagine a proton to look abit like this:

But then, the neutral pion is

What the feck does a root twoth of an up quark look like? What does "adding" quarks mean in terms of a single particle? Basically, I don't really know what this formula for a pion means.

Likewise with the gluons

and

Thanks.
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2. Right, so I imagine a proton to look abit like this:

But then, the neutral pion is

What the feck does a root twoth of an up quark look like? What does "adding" quarks mean in terms of a single particle? Basically, I don't really know what this formula for a pion means.

Likewise with the gluons

Thanks.
Good question. The expression

means that the neutral pion is actually expressed as a linear superposition of two possible states, these being and . The factor is there to normalise the expression, so that the total probability of the neutral pion being in either the or state doesn't exceed 1. It doesn't mean that of a quark is present!

Physically this means that when the pion is interacted with, the wavefunction describing it collapses into one of these flavour states. The one it is forced into is the one which would conserve flavour etc. For an example, look at the feynmann diagram for decay (found here http://teachers.web.cern.ch/teachers...n/exampl31.gif

See that the neutral pion is here considered to be This is because this quark combination is required to allow the d quark to be produced by the boson: if the neutral pion was the combination instead then charge conservation would be violated.

What does "adding" quarks mean in terms of a single particle?
With respect to this question, adding quarks like this really means that when the particle is freely propagating (i.e. interacting only with the Higgs field) it does not have a well defined flavour eigenstate. Put more simply, without interacting with it in such a way that determines its flavour, the observer can't tell if it is or simply from properties like its charge, mass etc. The Higgs field won't differentiate between the two combinations, as the u and d are pretty much degenerate in terms of mass (i.e. mass of mass of . For verification of this, compare the mass of a proton (uud) to that of a neutron (udd)) and so look the same in terms of mass measurements.

A similar principle applies with gluons - quote me if you want to know more.

I hope this makes at least some sense - not sure exactly what level of answer you're looking for here!

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