My understanding was that a meson, being made of a quark and an antiquark (spin 1/2) could only have spin 1 or 0, by addition of angular momentum states. I just saw an article announcing the discovery of a spin 3 excited state of a meson. How can an excited state of a meson have spin greater than 1?
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The total angular momentum of a meson is the sum of the spins of the two quarks and their orbital angular momentum. Excited states can have $L>0$ and therefore $J>1$.
answered Oct 14, 2014 at 7:01
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2$\begingroup$ But this doesn't seem to just be a meson with total angular momentum J=3; the article specifically says it has spin-3. Clarify? $\endgroup$– nkmCommented Oct 15, 2014 at 13:47
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2$\begingroup$ Language barrier. "Spin a" for a meson is a synonym for J*=*a. The above answer is unimpeachable, and you may flesh it out from elementary meson spectroscopy combination rules, en.wikipedia.org/wiki/… $\endgroup$ Commented Feb 17, 2016 at 22:20
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3$\begingroup$ Your quark antiquark pair may combine into a spin singlet or triplet (spin=1), but when the orbital angular momentum between these two quarks is 3 in the first case, or 2 or 3 in the second, the total *J*=3. You cannot distinguish between integral "spin" or "angular momentum" for a meson. $\endgroup$ Commented Feb 17, 2016 at 22:28