# Homework Help: Quark content of particles

1. Apr 3, 2014

### BOYLANATOR

1. The problem statement, all variables and given/known data

Write down the quark content of the following particles, made of (u; d; s) and their antiquarks:

(a) A meson with strangeness S = 1, and isospin component I3 = 1/2

(b) An antibaryon with strangeness S = 0, and isospin I3 = -3/2

3. The attempt at a solution

a) A meson consists of one quark and one antiquark. The strangeness comes from an anti-strange quark and an up quark satisfies the isospin So we have $u\bar{s}$

b) The antibaryon must have three antiquarks and in this case none can be strange. In order to have isospin of -3/2 we must have three antiup quarks, ie $\bar{u}\bar{u}\bar{u}$

My answer for a) is correct and b) seems ok.

Here is the given solution to b).

"An antibaryon contains three antiquarks. There can be no strange antiquarks if S=0 Also,
isospin component I3 = -3/2 tell us there must be three antiup quarks. So the answer is $\bar{d}\bar{d}\bar{d}$."

This is just a typo at the end, right?

Last edited: Apr 3, 2014
2. Apr 4, 2014

### lightgrav

If they had wanted a (regular) baryon, it would have been ddd , right?
I'll bet the question WAS originally (previous edition) for a baryon with I3 = - 3/2
When they changed the problem (for the new edition), the editor changed the (regular) to anti-,
but didn't notice that he also needed to negate the isospin projection (or change d to u in the solution).

3. Apr 4, 2014

### BOYLANATOR

Thanks. I just wanted to make sure as this stuff is new to me.