# Quark-antiquark creation in strong interactions

1. May 14, 2013

### sunrah

(please note this is similar to a homework question I have posted but it is not the same and here I am just trying to understand a concept)

In a book I was reading it said

$\Delta^{+} \longrightarrow n + \pi^{+}$

is a viable process via the strong force because all that is needed is a down antidown quark pair, which can be provided via the strong force. My question is why? If $\Delta^{+}$ is uud and $\Delta^{+}\pi^{+}$ is udd + $u\bar{d}$ we can see that the right hand side only has one antidown quark therefore there has only been one quark-antiquark pair created. Converting one quark into two only creates one extra particle effectively so I see a deficit on the left hand side.

Last edited: May 14, 2013
2. May 14, 2013

### Bill_K

Δ+ → n + π0

What you have written does not conserve charge.

3. May 14, 2013

### sunrah

You're right. I've changed it now it. My question really is about how a 3 quark particle can become two particles with a total of 5 quarks

we don't do this stuff in lectures

4. May 14, 2013

### Hepth

The process would be

d -> d + g -> d + (q qbar)

A gluon gets emitted that then decays. You're thinking its one d decaying to two, when its really 1 to 3

5. May 14, 2013

### sunrah

oh I see. does the q-qbar-pair have to be the same type? If I understand it right in this case the gluon must become an up and an antidown pair.

6. May 14, 2013

### Hepth

The q can be anything, but not mixed. A pi0 is not u dbar. It is u ubar and d dbar.

7. May 14, 2013

### sunrah

sorry my question was wrong. it should have been pi+

does this mean this process is forbidden?

8. May 14, 2013

### Hepth

I'll write ubar as u~

You have
uud > udd + ud~
So quark content is fine.

Draw it out, the gluon makes a d d~ but the d goes to the neutron, the d~ to the pion.

9. May 14, 2013

### sunrah

I think it just went click.
The Delta+ decays into two parts (e.g. ud and u) thereby producing a gluon which becomes dd~ pair except the d is taken up by ud to form a neutron and d~ joins with u to form a pi+.

Is that more or less right?

10. May 14, 2013

### Hepth

Yes that is correct.