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Homework Help: Quark content of particles

  1. Apr 3, 2014 #1
    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 [itex]u\bar{s}[/itex]

    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 [itex]\bar{u}\bar{u}\bar{u}[/itex]

    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 [itex]\bar{d}\bar{d}\bar{d}[/itex]."

    This is just a typo at the end, right?
    Last edited: Apr 3, 2014
  2. jcsd
  3. Apr 4, 2014 #2


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    Homework Helper

    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).
  4. Apr 4, 2014 #3
    Thanks. I just wanted to make sure as this stuff is new to me.
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