https://doi.org/10.1051/epjconf/201817506019
Structure of the Nucleon and its Excitations
1
Special Research Centre for the Subatomic Structure of Matter (CSSM), Department of Physics, University of Adelaide, Adelaide, South Australia 5005, Australia
2
School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China
3
ARC Centre of Excellence for Particle Physics at the Terascale (CoEPP), Department of Physics, University of Adelaide, Adelaide, South Australia 5005, Australia
* Speaker, e-mail: derek.leinweber@adelaide.edu.au
Published online: 26 March 2018
The structure of the ground state nucleon and its finite-volume excitations are examined from three different perspectives. Using new techniques to extract the relativistic components of the nucleon wave function, the node structure of both the upper and lower components of the nucleon wave function are illustrated. A non-trivial role for gluonic components is manifest. In the second approach, the parity-expanded variational analysis (PEVA) technique is utilised to isolate states at finite momenta, enabling a novel examination of the electric and magnetic form factors of nucleon excitations. Here the magnetic form factors of low-lying odd-parity nucleons are particularly interesting. Finally, the structure of the nucleon spectrum is examined in a Hamiltonian effective field theory analysis incorporating recent lattice-QCD determinations of low-lying two-particle scattering-state energies in the finite volume. The Roper resonance of Nature is observed to originate from multi-particle coupled-channel interactions while the first radial excitation of the nucleon sits much higher at approximately 1.9 GeV.
This research was undertaken with the assistance of resources at the NCI National Facility in Canberra, the iVEC facilities at the Pawsey Centre and the Phoenix GPU cluster at the University of Adelaide, Australia. These resources were provided through the National Computational Merit Allocation Scheme, supported by the Australian Government, and the University of Adelaide through their support of the NCI Partner Share and the Phoenix GPU cluster. This research was supported by the Australian Research Council through the ARC Centre of Excellence for Particle Physics at the Terascale (CE110001104) and through Grants No. DP151103101 (A.W.T.), DP150103164, LE120100181 and LE160100051 (D.B.L.).
© The Authors, published by EDP Sciences, 2018
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (http://creativecommons.org/licenses/by/4.0/).
