Symmetries of higher-spin fields and the electromagneticN→N*(1680)form factors

Abstract

We study the Q 2 evolution of the form factors (FFs) for the nucleon-to-N * (1680) transition in the framework of effective field theory. To this end, the intrinsic symmetries of the spin-5 2 Rarita-Schwinger (RS) fields are analyzed, and a Lagrangian of the electromagnetic NN * (1680) interactions is constructed. The Lagrangian preserves all the intrinsic symmetries of the spin-5 2 field-point and gauge invariance-and does not involve lower-spin components of the reducible RS field. In addition, the symmetries postulate the definitions of the Lagrangian FFs. These FFs are modeled as dispersionlike expansions in a vector-meson-dominance model. A good agreement with the experimental data is achieved.

Gauge- and point-invariant vertices of nucleon-to-resonance interactions

“…The point-and gauge-invariant interactions were studied earlier for spin- 3 2 and - 5 2 in Refs. [23][24][25][26]. In this work, we generalize the results of Refs.…”

“…In this work, we generalize the results of Refs. [25,26] to the case of arbitrarily high spin of the resonance. An outline of the rest of the paper is given below.…”

Quark-hadron duality in lepton scattering off nuclei

“…Electromagnetic and weak vector form factors were determined in [20] by fitting the electroproduction data on helicity amplitudes in the region Q 2 < 3 GeV 2 . Recently, it was shown [22] that in order to satisfy the asymptotics for helicity amplitudes at Q 2 → ∞, as prescribed by perturbative QCD, the vector form factors should also exhibit a certain asymptotic Q 2 behavior. Therefore, we refitted the form factors according to this prescription.…”

“…, however, the difference between our new fit and the one performed in [20] falls within the accuracy of the experimentally extracted helicity amplitudes. To be on the safe side for higher Q 2 values, further attempts to improve the fits of the form factors (for example, in accordance to upcoming data on helicity amplitudes) will be done within the framework of the arguments presented in [22]. The axial form factors are the ones used in [13] for the "fast" fall-off case.…”

Nucleon-to-resonance transition form factors in a vector-meson-dominance model

“…ΨĀ is a gauge invariant tensor spinor made of the RS field operator and derivatives; V λ 1 σ 1 are field tensors of the vector fields V = γ, ρ(770), ω(785), ρ(1450),...; γ R = 1 for tensor-spinor resonances J P = (3/2) − , (5/2) + ,... and γ R = iγ 5 for pseudotensor-spinor ones J P = (3/2) + , (5/2) − ,... For the lowest spins J = 3/2, 5/2 the Lagrangian (2.2) was constructed in Refs. [6,7].…”