arXiv subjects
Publications and source records attributed to H. Hogaasen.
Hadronic spectroscopy can be introduced to students and developed rather far without requiring SU(N) flavour symmetry. In such a "minimalist" presentation, we are naturally led to comment and clarify the concept of the "generalized" Pauli principle.
The chromomagnetic interaction, with proper account for flavour-symmetry breaking, is shown to explain the mass and coupling properties of the X(3872) resonance as a $J^{PC}$ = 1$^{++}$ state consisting of a heavy quark-antiquark pair and a light one. It is crucial to introduce all the spin-colour configurations compatible with these quantum numbers and diagonalise the chromomagnetic interaction in this basis. This approach thus differs from the molecular picture $D\bar {D}*$ and from the diquark-antidiquark picture.
We study the properties of coloured three particle s-wave quark clusters when flavour symmetry is broken. The relevance of such clusters for models of pentaquarks is shortly mentioned.
We study the properties of the colour triplet qqqbar quark cluster when flavour symmetry is broken. The relevance of such a cluster for some models of pentaquarks is then examined in the light of recent experimental signals.
The simple independent quark models have difficulties explaining simultaneously the totality of the known hyperon magnetic moments and hyperon semi-leptonic decay rates. We show that both the Goldstone boson loop contributions and the two-quark effective exchange currents are essential in explaining these observables.
We discuss a model for heavy mesons where the light quark (u or d) moves in the colour electric field from a heavy quark (c or b) placed in the center of the bag. We calculate energy spectra for pionic and photonic transitions from excited states. The transition amplitudes and the branching ratios between electromagnetic and pionic transitions compares favorable with the limited amount of known experimental data.
We explore the influence on the Isgur-Wise function of the colour electric potential between heavy and light quarks in mesons. It is shown that in bag models, its inclusion tends to restore light quark flavour symmetry relative to the MIT bag predictions, and that relative to this model it flattens the Isgur-Wise function. Results compare very well with observations.