G. Dillon

General QCD parametrization of the charge radii of p , n and Δ+

Abstract Using the general parametrization method we discuss the relation: r 2 ( p )− r 2 ( n )= r 2 ( Δ + ) between the charge radii of p , n and Δ + derived in a recent quark model calculation of Buchmann, Hernandez and Faessler [Phys. Rev. C 55 (1997) 448]. We show that the above relationship is obtained by the general parametrization if one excludes three index and closed loop terms, which are indeed absent in the model quoted above; this checks the correctness of the calculation of Buchmann et al. on this point. However in QCD, where three index terms exist, arising e.g. from two gluon exchanges between three different quark lines, the above relationship is modified; an estimate indicates that this modification should be between 10% and 20%.

Δ photoexcitation in nuclei

Abstract A sum rule for the total nuclear photoabsorption in the Δ region is derived. Due to the NΔ mass difference, the integrated cross section is predicted to be essentially proportional to the nucleon number. A self-consistent model for the Δ propagation in nuclear matter is successfully applied to the description of the cross section as a function of the energy.

Baryon octet magnetic moments to all orders in flavor breaking: An application to the problem of the strangeness in the nucleon

Using the general QCD parametrization (GP) we display the magnetic moments of the octet baryons including all flavor breaking terms to any order. The hierarchy of the GP parameters allows to estimate a parameter

Electron scattering sum rule in the Δ region

g_{0}

On the miracle of the Coleman–Glashow and other baryon mass formulas

related to the quark loops contribution of the proton magnetic moment; its order of magnitude is predicted to be inside a comparatively small interval including the value given recently by Leinweber et al. by a lattice QCD calculation

QCD parametrization of the ργ, ωγ and Φγ couplings: whyfργ:fωγ=3:1 in spite of flavor breaking

Abstract A sum rule is derived for the transverse response function R T measured in (e,e′) in the Δ region. Within “Δ dominance” the energy integrated R T at fixed momentum transfer is shown to be linear with A and, to a large extent, model independent.

Self-consistency in π- and Δ- propagation in nuclear matter

Abstract Due to a new measurement of the Ξ0 mass, the Coleman–Glashow formula for the baryon octet e.m. masses (derived using unbroken flavor SU3) is satisfied to an extraordinary level of precision. The same unexpected precision exists for the Gell Mann–Okubo formula and for its octet-decuplet extension (G. Morpurgo, Phys. Rev. Lett. 68 (1992) 139). We show that the old question “why do they work so well?” is now answered by the general parametrization method.

A relation between the charge radii of π+,K+,K0 derived by the general QCD parametrization

AbstractA quasi no flavor breaking theorem, derived from QCD for a class of hadronic states, is used to show that the ratio of ϱγ to ωγ coupling-for ideal ω-ϕ mixing-is almost (to a part in 102) unaffected by flavor breaking, and, therefore, equal to 3. On the other hand the ratio of ϱγ to ϕγ coupling, (not governed by the theorem) must differ, due to flavor breaking, from the unbrokenSU3 value

Some properties of the magnetic moments of the Δ′s in QCD

(3/\sqrt 2 )