The electroproduction of the Δ(1232) in the chiral quark–soliton model

Abstract

We calculate the ratios E2/M1 and C2/M1 for the electroproduction of the ∆ (1232) in the region of photon virtuality 0 <−q 2 < 1 GeV 2 . The magnetic dipole amplitude M1 is also presented. The theory used is the chiral quark-soliton model, which is based on the instanton vacuum of the QCD. The calculations are performed in flavours SU(2) and SU(3) taking rotational (1/N c ) corrections into account. The results for the ratios agree qualitatively with the available data, although the magnitude of both ratios seems to underestimate the latest experimental results.

Electromagnetic properties of theΔ(1232)and decuplet baryons in the self-consistentSU(3)chiral quark-soliton model

“…The whole G χ E2 form factor originates from the rotational corrections and therefore scales as 1/N c and vanishes in the large N c limit. The same density also occures in the χQSM expression for the N − ∆ transition form factor ratios [38]. The final results of that χQSM SU (3) analysis are E2/M 1 = −1.4% and C2/M 1 ≈ −1.8% for which we can write…”

“…by using the formulae presented in [38]. Inserting the density I 1E2 (r) of this work reproduces the 0.78.…”

Signatures of chiral dynamics in the nucleon to Delta transition⋆

“…[39,41] are unfortunately at too large pion-masses to be relevant for the chiral extrapolation functions presented here. However-independent of this (present) limitation of 15 We note again that all chiral extrapolation functions shown in this work implicitly assume that all accompanying mass factors in the definition of the N ∆-transition current are held at their physical values. The behaviour of the chiral extrapolation functions changes significantly for mπ > 200 MeV when the effects of the quark-mass dependence of these masses are also included [27].…”

Measurement of the LT-asymmetry in πelectroproduction at the energy of the Δ(1232)-resonance

“…Within constituent quark models those components originate from tensor forces generated by a color hyperfine interaction [1,2,3,4]. Larger quadrupole strengths are expected from models emphasizing the particular role of pions via exchange currents [5] or the 'pion cloud' [6,7,8,9,10], and also in first quenched Lattice QCD calculations [14]. Dynamical approaches [11,12,13] enable a decomposition into the "bare" contributions, as described in quark models, and the "dressing" by the pion cloud.…”