# Quark content of neutral pion

1. Oct 27, 2013

### websterling

The quark content of the neutral pion is listed as $\frac{u\overline{u}-d\overline{d}}{\sqrt{2}}$ What is the proper way to interpret this?

2. Oct 27, 2013

### fzero

Can you elaborate? Is your question related to the quantum mechanical interpretation of a superposition of states, or is it more directly related to particle physics? If it is about particle physics, then perhaps the more appropriate way to look at this superposition is as a consequence of the approximate isospin symmetry.

3. Oct 27, 2013

### tiny-tim

what is $\frac{u\overline{u}+d\overline{d}}{\sqrt{2}}$ ?

4. Oct 27, 2013

### websterling

That should be a "-" instead of a "+" in the expession- it was correct in my original post.

In, for example, the Wikipedia Pion article, the positive pion's quark composition is listed as $u\overline{d}$, and the neutral pion's composition is listed as $u\overline{u}$ or $d\overline{d}$

Additionally, the neutral pion's quark content is listed as$\frac{u\overline{u}-d\overline{d}}{\sqrt{2}}$

My question is, from a particle physics standpoint, how is $\frac{u\overline{u}-d\overline{d}}{\sqrt{2}}$ related to $u\overline{u}$ or $d\overline{d}$?

5. Oct 27, 2013

### UltrafastPED

It represents a superposition of the two; the sqrt(2) is the normalization factor.