Tetraquarks, Pentaquarks and Dibaryons in the large NN QCD

We study the multiquark hadrons in large $N$ QCD under the 't-Hooft limit, extending Witten's picture of the baryons. We explore the decay widths of tetraquarks, pentaquarks and dibaryons. Based on the decay behaviors, we point out in the $N\to \infty$ limit decay widths of tetraquarks stay constant, while those of pentaquarks and dibaryons above certain thresholds can diverge. In the large $N$ limit, we find that the ground states of the three spectroscopic series are stable or narrow and that the excited states of pentaquarks and dibaryons above the indicated thresholds are not observables. We compare our results with those obtained in a different large $N$ generalization of tetraquarks.Comment: 9 pages, 6 figures; v2: discussions on phase space added in the appendi

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

Diquarks are found to have the right degrees of freedom to describe the tetraquark poles in hidden-charm to open-charm meson-meson amplitudes. Compact tetraquarks result as intermediate states in non-planar diagrams of the 1/N expansion and the corresponding resonances are narrower than what estimated before. The proximity of tetraquarks to meson-thresholds has an apparent role in this analysis and, in the language of meson molecules, an halving rule in the counting of states is obtained

Diquark-antidiquark states with hidden or open charm

Some features and predictions of a recently proposed model based on diquark-antidiquark bound states are illustrated. Its ability in accomodating newly discovered charmed resonances around 4 GeV is discussed.Comment: To appear in the proceedings of the HEP2005 International Europhysics Conference on High Energy Physics, July 21st-27th 2005, Lisboa, Portuga

Doubly Heavy Tetraquarks in the Born-Oppenheimer approximation

Tetraquarks Q Q qbar qbar are found to be described remarkably well with the Quantum Chromodynamics version of the Hydrogen bond, as treated with the Born-Oppenheimer approximation. We show the robustness of the method by computing the mass of the observed T_cc tetraquark following two different paths. Relying on this, we provide a prediction for the mass of the expected T_bb particle.Comment: 8 pages, 1 figur

Probing minimal supersymmetry at the LHC with the Higgs boson masses

The ATLAS and CMS collaborations report indications of a Higgs boson at Mh ~ 125 GeV. In addition, CMS data show a tenuous bump in the Z Z channel, at about 320 GeV. We make the bold assumption that it might be the indication of a secondary line corresponding to the heaviest scalar Higgs boson of minimal supersymmetry, H, and discuss the viability of this hypothesis. We discuss also the case of a heavier H. The relevance of the bb* decay channel is underlined

The pentaquark spectrum from Fermi statistics

We study compact hidden charm pentaquarks in the Born–Oppenheimer approximation, previously introduced for tetraquarks, assuming the heavy pair to be in a color octet. We show that Fermi statistics applied to the complex of the three light quarks, also in color octet, requires S-wave pentaquark ground states to consist of three octets of flavour-SU(3)$$_f$$, two with spin 1/2 and one with spin 3/2, in line with the observed, strangeness $$S=0,-1$$, spectrum. Additional lines corresponding to decays into $$J/\psi +\Sigma$$ and $$J/\psi +\Xi$$ are predicted. In the language of non-relativistic SU(6), ground state pentaquarks form either a {\varvec{56}} or a {\varvec{20}} representation, distinguished by presence or absence of pentaquarks decaying in the spin 3/2 decuplet, e.g. in $$J/\psi +\Delta ^{++}$$. Observation of a strangeness $$S=-2$$ or isospin $$I=3/2$$ pentaquarks would be a clear signature of compact, QCD bound pentaquarks