Covariant tetraquark equations in quantum field theory
Abstract
We derive general covariant coupled equations of QCD describing the tetraquark in terms of a mix of four-quark states 2q2 q, and two-quark states q q. The coupling of 2q2 q to q q states is achieved by a simple contraction of a four-quark q q-irreducible Green function down to a two-quark q q Bethe-Salpeter kernel. The resulting tetraquark equations are expressed in an exact field theoretic form, and are in agreement with those obtained previously by consideration of disconnected interactions; however, despite being more general, they have been derived here in a much simpler and more transparent way.
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