title: Completing the Picture of the Roper Resonance.
abstract: We employ a continuum approach to the three valence-quark bound-state problem in relativistic quantum field theory to predict a range of properties of the proton's radial excitation and thereby unify them with those of numerous other hadrons. Our analysis indicates that the nucleon's first radial excitation is the Roper resonance. It consists of a core of three dressed quarks, which expresses its valence-quark content and whose charge radius is 80% larger than the proton analogue. That core is complemented by a meson cloud, which reduces the observed Roper mass by roughly 20%. The meson cloud materially affects long-wavelength characteristics of the Roper electroproduction amplitudes but the quark core is revealed to probes with Q(2)≳3m(N)(2).
authors.affiliation: Grupo de Física Nuclear and Instituto Universitario de Física Fundamental y Matemáticas (IUFFyM), Universidad de Salamanca, E-37008 Salamanca, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Segovia
authors.affiliation: Laboratório de Física Teórica e Computacional, Universidade Cruzeiro do Sul, 01506-000 São Paulo, SP, Brazil.|Instituto de Física Teórica, Universidade Estadual Paulista, 01140-070 São Paulo, SP, Brazil.
authors.forename: Bruno
authors.initials: B
authors.lastname: El-Bennich
authors.affiliation: Laboratório de Física Teórica e Computacional, Universidade Cruzeiro do Sul, 01506-000 São Paulo, SP, Brazil.|Instituto de Física, Universidad de Antioquia, Calle 70 No. 52-21, Medellín, Colombia.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Rojas
authors.affiliation: Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Ian C
authors.initials: IC
authors.lastname: Cloët
authors.affiliation: Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Craig D
authors.initials: CD
authors.lastname: Roberts
authors.affiliation: Department of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Shu-Sheng
authors.initials: SS
authors.lastname: Xu
authors.affiliation: Department of Physics, Nanjing University, Nanjing 210093, China.
authors.forename: Hong-Shi
authors.initials: HS
authors.lastname: Zong