Nucleon resonances in AdS/QCD

Abstract

We describe the electroproduction of the N(1440) Roper resonance in soft-wall AdS/QCD. The Roper resonance is identified as the first radially excited state of the nucleon, where higher-Fock states in addition to the three-quark component are included. The main conclusion is that the leading 3q component plays the dominant role in the description of electroproduction properties of this resonance: form factors, helicity amplitudes and charge densities. The obtained results are in good agreement with the recent results of the CLAS Collaboration at JLab.Comment: 20 pages. arXiv admin note: text overlap with arXiv:1204.661

Parameters of scalar resonances from the combined analysis of data on processesππ→ππ,KK¯Surovtsev1, Bydžovský2, Kamiński3 et al. 2014Phys. Rev. DSelf Cite84110View full textAdd to dashboardCite

“…This prediction is also in agreement with a refined analysis using the large-N c consistency conditions between the unitarization and resonance saturation which suggests m ρ − m σ = O(N −1 c ) [29]. In addition, in the soft-wall anti-de Sitter/QCD approach [30] -the approach based on gauge/gravity duality -the predicted mass of the lowest f 0 meson, 721 MeV, practically coincides with the value obtained in our work. The above discussion concerns solution B, which is prefered by the analysis presented in this paper.…”

Baryons as relativistic three-quark bound states

“…They exhibit a strong Q 2 dependence of the transverse helicity amplitude A 1/2 including a zero crossing, which also translates into a zero of the corresponding Pauli form factor F 2 (Q 2 ). Such a behavior is typically expected for radial excitations and it has been recovered by a number of approaches, from constituent [23] and light-front constituent-quark models [24] to Dyson-Schwinger calculations [25], effective field theory [26], lattice QCD [27] and AdS/QCD [28]. Although none of them has yet achieved pointwise agreement with the data they all predict the correct signs and orders of magnitude of the amplitude.…”

“…2, are in striking contrast to the ratio obtained via LT or Rosenbluth separations, showing an approximately linear decrease of R with Q 2 which is in strong violation of the Q 2 scaling behavior (see also Refs. [1,2,28,29]). The discrepancy between the LT and PT measurements of G E /G M has stimulated considerable activity, both theoretically and experimentally, over the past decade.…”

Electroproduction of lightest nucleon resonances up to Q*2=12 GeV*2 in quark models at light front

“…Light-front quark wave functions were successfully used by many authors for description of nucleon form factors and transition amplitudes as before appearance of the polarized electron data [3][4][5] as well as after these (taking into account new high-quality data) [6][7][8][9]. However these works used the data up to Q 2 3-4 GeV 2 which were only available.…”