A consistent explanation of the Roper phenomenology

Abstract

We study the electromagnetic transitions of the Roper N(1440) resonance. Our results, when combined with the previously obtained for the mass and the pionic strong decay widths of the Roper, show that within a non-relativistic constituent quark model scheme, a comprehensible understanding of the Roper phenomenology can be achieved. They also seem to support the view of the Roper as a radial excitation of the nucleon, though more experimental data are needed to reach a definitive conclusion.Comment: 14 pages, 4 figures (7 postscript files). Some referencess adde

Electromagnetic structure of the nucleon and the Roper resonance in a light-front quark approach

“…Since direct QCD calculations are difficult in the low-energy regime several models for the electroexcitation of the Roper resonance were proposed during the last three decades [15][16][17][18][19][20][21][22] (see reviews [23,24] for details). Now model predictions can be compared to the new high-quality photo-and electroproduction data [1][2][3].…”

“…In our case we have S ′ = 1 2 (the canonical nucleon spin), but after Melosh rotations of the quark spins this value transforms into two different values, S = 01 in Eq. (6) we obtain the correct basis vectors in the product space (the LF spin S and the LF momentum P ) for the irreducible representation (IR) [21] P S of the permutation group S 3…”

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.…”