Mesons: Questions and Antiquestions

       
Project Home - Prior Knowledge - Project Context - Resources



Is that glint in the Meson Kelpie's eye just a reflection of the Australian sun or the satisfaction of sharing a name with a whole class of subatomic particles? Does the mirror image of the Kelpies tell us something about mesons?

In fact, mesons are hadrons composed of quark-antiquark pairs. Look at the chart below and see if you can correctly predict the charges of several mesons.


Quark Flavor Mass (GeV) Electric Charge
up (u) 0.003 2/3
down (d) 0.006 -1/3
charm (c) 1.3 2/3
strange (s) 0.1 -1/3
top (t) 175 2/3
bottom (b) 4.3 -1/3


Find the charge of each meson:

  1. PI + (up-antidown) _______

  2. K - (strange-antiup)_______

  3. RHO + (up-antidown)_______

  4. ETA-C (charm-anticharm)_______

  5. UPSILON (bottom-antibottom)________

  6. D + (charm-antidown)________

Check Your
Answers Here!

Now, try finding the mass of each meson above by adding the masses of its constituent quarks.

The Meson Table checks and analyzes your results.


After you have examined and analyzed the data, consider these questions . . .


  1. How, if at all, does the sum of the quark masses in a meson indicate what the meson mass will be?

  2. Is there some sort of proportionality between net quark mass mq and meson mass Mm?

  3. Can you write an empirical mathematical equation relating net quark mass mq and meson mass Mm?

  4. What is the significance of the realtionship you found between mq and Mm?

  5. How do you explain this relationship in terms of the physics involved in binding a quark and an antiquark to make a meson?