Particle Physics course follow up

I am just following up on my OpenLearn particle phyiscs course review follow up.

As part of this I had to work out the charge spectrum on groups of 3 quarks.

This short article explains (or tries to) how to do this. Firstly thank to the course creators, Open Learn and the Open University without whom the course would not have been possible. Thank you also to users on the physics irc channel who gave me some help with doing this.

So if we take a Proton as an example, this has 3 quarks


so firstly I had to write down all the possible combinations

uuu uud udu udd duu dud ddu ddd

There are repeated combiations here so by removing these we get

uuu ddd duu ddu

From here we then need to list the charges associated with each, and calculate totals

uud = 2/3 + 2/3 + 2/3 = +2e ddd = -1/3 + -1/3 + -1/3 = -1e duu = -1/3 + 2/3 + 2/3 = 1e ddu = -1/3 + -1/3 + 2/3 = 0

Now list the totals

+2e -1e 1e 0

if we put them in some sort of order

-1e 0 1e +2e

We get the charge spectrum

The activity had a sort of frurt machine that would come up with combinations of all the 6 quarks

u d s c t b

Details of where they fit in to the standard model and associated charges can be found on the standard model table.

This may sound complex, which is perfectly fine, once it was explained to be, and someone worked through it, it was much clearer, I decided to write it all down, and then type up here, as this helps to reinforce learning.

Given there are 6 quarks, the number of different combinations of 3 quarks is huge. Then think there would be anti baryons, so the same combination but with antiquarks

Mesons have combinations of 1 quark and 1 antiquark.