Are there tetraquarks at largeNcin QCD(F)?

Abstract

Weinberg recently pointed out a flaw in the standard argument that large Nc QCD with colorfundamental quarks [QCD(F)] cannot yield narrow tetraquark states. In particular, he observed that the argument does not rule out narrow tetraquarks associated with the leading-order connected diagrams; such tetraquarks would have a width scaling as N −1 c . It is shown here, however, that while the standard analysis of tetraquarks does not rule them out, a more thorough analysis rules out quantum-number exotic tetraquarks associated with the leading-order connected diagrams. This analysis is based entirely on conventional assumptions used in large Nc physics applied to the analytic properties of meson-meson scattering. Our result implies that one of three possibilities must be true: i) quantum-number exotic tetraquarks do not exist at large Nc; ii) quantum-number exotic tetraquarks exist, but are associated with subleading connected diagrams and have anomalously small widths that scale as N −2 c or smaller; or iii) the conventional assumptions used in large Nc analysis are inadequate.

Tetraquarks in the 1/N expansion and meson-meson resonances

“…In [36] it is shown that the Coleman-Witten lore that no tetraquarks occur at large N is not related to the fact that they did not consider all possible ways of cutting the diagrams. Therefore, tetraquarks can be made the way suggested in [31], but with the concerns discussed in [37].…”

$$Y(4260)\rightarrow \gamma + X(3872)$$ Y ( 4260 ) → γ + X ( 3872 ) in the diquarkonium picture

“…Tetraquarks in large-N QCD have been further studied in [5][6][7]. The recent discovery of two pentaquark states of opposite parity [8] has reinforced the case for a new spectroscopic series of hadrons, in which diquarks (antidiquarks) replace antiquarks (quarks) in the classical scheme [9,10].…”

Theory of baryon resonances at largeNc

“…During the refereeing we have been informed that the complete tables of isoscalar coefficients were presented in [47]. The tables presented here are analogous and differs only method of calculation.…”