# Strong or weak force?

1. Mar 10, 2012

### R0CC0

Strong or weak force??

1. The problem statement, all variables and given/known data
So all I want to know is how you tell if it is a strong or weak force interaction.
e.g. K^+ = pi^0 + pi^0 + pi^+ (all mesons)

So i determined that the energy was concerved:
493.7-135-135-139.6=84.1MeV

baryon and Lepton numbers are also conserved
(0)=(0)

Now having determined that the interaction is possible, how do I tell if it is via strong or weak force.

2. Mar 12, 2012

### gomboc

Re: Strong or weak force??

The key here is to look at the quark content of the reactants and products. A positive kaon has an up and an anti-strange quark. Yet none of the pions contain a strange/anti-strange quark.

What is the only interaction capable of changing the flavour of quarks?

3. Mar 12, 2012

### R0CC0

Re: Strong or weak force??

So in this case weak force?

4. Mar 12, 2012

### gomboc

Re: Strong or weak force??

The weak force is the only interaction that can change the flavour of a quark. The strong force can't.

5. Mar 12, 2012

### R0CC0

Re: Strong or weak force??

Righto Got it now. Thanks!