Electroproduction of the Roper resonance and the constituent quark model

Abstract

A parameter-free evaluation of the $N - P_{11}(1440)$ electromagnetic transition form factors is performed within a light-front constituent quark model, using for the first time the eigenfunctions of a mass operator which generates a large amount of configuration mixing in baryon wave functions. A one-body electromagnetic current, which includes the phenomenological constituent quark form factors already determined from an analysis of pion and nucleon experimental data, is adopted. For $Q^2$ up to few $(GeV/c)^2$, at variance with the enhancement found in the elastic channel, the effect of configuration mixing results in a significant suppression of the calculated helicity amplitudes with respect to both relativistic and non-relativistic calculations, based on a simple gaussian-like ansatz for the baryon wave functions.Comment: revised version to appear in Phys. Lett.

Electron- and neutrino-nucleus scattering from the quasielastic to the resonance region

“…However, the present experimental status does not allow any conclusions on the strange transition form factors, thus, we neglect them in this work and set F s i and F s A to zero. Several studies have addressed the properties of the P 11 (1440) as well as its electromagnetic and weak production [40,41,42,43,44,45,46,47]. In the works of Refs.…”

Electromagnetic transition form factors of the Roper resonance in a phenomenological field theory

“…Even though the empirical data for the transverse and scalar (longitudinal) helicity amplitudes can be described fairly well for larger values of the squared momentum transfer in the framework of relativistic quark models as well as in lattice QCD, neither of the two approaches predicts the behavior in the low-Q 2 region correctly [9,12,29,33,37,39,40]. The aim of this article is to investigate the electromagnetic nucleon-to-Roper-resonance transition form factors in the framework of low-energy effective field theory (EFT) which is based on chiral perturbation theory [41,42] (see, e.g., Refs.…”

Valence quark contributions for theγN→P11(1440)form factors

“…The γN → P 11 (1440) transition amplitudes have been studied in several ways: treating the Roper as a quarkgluon system [12], a pure valence quark system [4,[13][14][15][16][17][18], and a valence quark system dressed by qq pairs [19][20][21][22][23]. Relativity has proven to be very important, not only for a large Q 2 , but also for the region Q 2 ∼ 0.…”