Constraints from the 1 / N c Expansion on Properties of Exotic Tetraquark Mesons
D. Melikhov*, W. Lucha and H. Sazdjian
Pre-published on:
February 19, 2018
Published on:
March 20, 2018
Abstract
Scrutinizing the scattering of ordinarymesons in the limiting case of the number of colour degrees of freedomNc of quantumchromodynamics approaching infinity, we formulate Feynman-diagram selection criteria and from these deduce rigorous self-consistency conditions for the manifestation of a tetraquark, a two-quark–two-antiquark bound state, as a pole in the corresponding amplitudes. Our constraints bear rather far-reaching consequences: In particular, all flavour-exotic tetraquarks, composed of four (anti)quarks of disparate flavour, must come in, at least, two variants differing in (and thus readily identifiable by) the large-Nc behaviour of their couplings to two ordinary mesons. Quite generally, irrespective of their flavour composition, all tetraquarks prove to be narrow. Their decay rates behave, for large Nc, like 1/N2c and thus decrease faster than those of ordinary mesons.
DOI: https://doi.org/10.22323/1.310.0233
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