Magnetic moments of decuplet baryons in an independent particle potential model

Magnetic moments of decuplet baryons have been calculated in a relativistic independent quark model with a phenomenological potential in equally mixed scalar-vector harmonic form. Such a model has been successful in describing wide ranging hadronic phenomena in mesonic and baryonic sectors. Using the solutions of the constituent quark orbitals with the model parameters taken from its earlier applications, the magnetic moments of decuplet baryons Δ⁺⁺ and Ω⁻ have been obtained which are in good agreement with the available experimental data. However, the agreement is found to be much better when the magnetic moment ratios such as μ_δ++/μ _p and μ_Ω-/μ_Λ are considered. Model predictions for the magnetic moments of other decuplet baryons together with the charge radii have also been calculated which may be verified in future experiments.     

Electric quadrupole and magnetic octupole moments of the light decuplet baryons within light cone QCD sum rules

The electric quadrupole and magnetic octupole moments of the light decuplet baryons are calculated in the framework of the light cone QCD sum rules. The obtained non-vanishing values for the electric quadrupole and magnetic octupole moments of these baryons show nonspherical charge distribution. The sign of electric quadrupole moment is positive for Ω⁻, Ξ^*−, Σ^*− and negative for Σ^*+, which correspond to the prolate and oblate charge distributions, respectively. A comparison of the obtained results with the predictions of non-covariant quark model which shows a good consistency between two approaches is also presented. Comparison of the obtained results on the multipole moments of the decuplet baryons containing strange quark with those of Δ baryons shows a large SU(3) flavor symmetry breaking.     

Quadrupole moments of hadrons

We study an Abelian Higgs model in three, four and five dimensions using the mean field perturbation expansion with covariant gauge fixing. In four and five dimensions the mean field analysis shows three phases; a confined phase, a Coulomb phase with massless spin waves, and a Higgs phase in which the spin waves aquire a mass. The Higgs and confined phases are shown to be connected. In three dimensions we find a single phase.     

Magnetic moments of excited baryons

The explanation of the nucleon’s resonance spectrum is a long standing challenge. Magnetic moments of resonances are a valuable testing ground for baryon structure calculations. We have shown in a former experiment that the extraction of the Δ⁺(1232) magnetic dipole moment is feasible via the measurement and analysis of the reaction γp→π⁰γ^′p, in which the photon γ^′ carries the desired information. Such an experiment has been repeated with high precision using the Crystal Ball and TAPS detectors at the MAMI accelerator facility. Preliminary results will be presented. Furthermore, the perspectives for accessing the magnetic moment of the S₁₁(1535) resonance in radiative η photoproduction γp→ηγ^′p will be discussed.     

Charge radii of octet and decuplet baryons in chiral constituent quark model

The charge radii of the spin- $\frac{1}{2}^+$ octet and spin- $\frac{3}{2}^+$ decuplet baryons have been calculated in the framework of chiral constituent quark model (χCQM) using a general parametrization method (GPM). Our results are not only comparable with the latest experimental studies but also agree with other phenomenological models. The effects of SU(3) symmetry breaking pertaining to the strangeness contribution and GPM parameters pertaining to the one-, two- and three-quark contributions have also been investigated in detail and are found to be the key parameters in understanding the non-zero values for the neutral octet (n, Σ⁰, Ξ⁰, Λ) and decuplet (Δ⁰, Σ^*0, Ξ^*0) baryons.     

Quadrupole moments in the cadmium isotopes

Contrary to theoretical predictions and previous experimental results, a new systematic study of the static quadrupole moments Q₂₊ in the even-mass cadmium isotopes using the re-orientation effect shows no evidence of significant variation in Q₂₊ with mass number. For ¹¹⁶Cd, B(E2: 0⁺ → 2⁺) is found to be 20% lower than the previously adopted value.     

Color octet contribution in exclusive P-wave charmonium decay into octet and decuplet baryons

In the last years, the need for the color octet state in inclusive P-wave charmonium decay has been firmly established. However, the implications of this in the corresponding exclusive reactions have not been fully recognized. We argue for the necessity of the color octet in P- and higher-wave quarkonium decay. Using a set of phenomenologically constructed baryon wave functions, we consider the decay into an octet and decuplet baryon–antibaryon pair. By doing so, we subject the wave functions to a test of applicability. We show that the color singlet component alone is insufficient to account for the experimental measurements, and only by including the color octet contribution can the partial theoretical decay widths be brought into the range of the data. By the present and earlier applications of the set of wave functions, these show themselves to be reasonable model wave functions at around the scale –20 GeV. Received: 1 March 1999 / Published online: 18 May 2000     

Magnetic moments of the strange baryons in the bag model

We break SU(3) symmetry in the bag model by giving the singlet quark a mass m. The magnetic moment ratios of the strange baryons are calculated and compared with exact SU(6) predictions and with experiment.     

One-gluon exchange corrections to magnetic moments of baryons

One-gluon exchange (OGE) corrections to the magnetic moments of the octet baryons are studied in the bag model. It is clarified that OGE resolves a problem of μ(Λ) and μ(Ξ^?) in previous quark model calculations and also improves an overall agreement between theory and experiment.