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Bridging hadronic and vacuum structure by heavy quarkonia

Mar 27, 2024
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Abstract: (arXiv)
We discuss the central and, mostly, spin-dependent potentials in heavy quarkonia bˉb,cˉc\bar b b, \bar c c, with two goals in mind. The first is phenomenological: using the splitting between the 1S and 2S pairs, as well as the 1P and 2P quartet masses, we obtain very accurate values of all matrix elements of the spin-depepdent potentials. The second is theoretical: using standard wave functions, we compute these matrix elements, from perturbative, nonperturbative and ``string" contributions. The model for nonperturbative effects is a ``dense instanton liquid model", in which the QCD vacuum is made of (strongly color correlated) instanton-antiinstanton pairs or "molecules". We calcuate their effect via standard Wilson lines, with or without extra powers of gauge fields. We find that this model provides a reasonable description of all central, spin-spin and spin-orbit forces at distances r=00.7fmr= 0-0.7 \, fm , relevant for bˉb\bar b b and cˉc\bar c c quarkonia.
  • quarkonium: heavy
  • spin: dependence
  • instanton: liquid
  • liquid: model
  • effect: nonperturbative
  • quantum chromodynamics: vacuum state
  • Wilson loop
  • color
  • splitting
  • gauge field theory