The Beauty of Spin

Abstract

I review recent developments in theoretical spin physics. Topics include pion production in nucleon-nucleon collisions, the implications of heavy quark spin symmetry for heavy hadron molecules, the nucleon electric dipole form factors and ab initio calculations of the width of hadron resonances. A few spin physics high-lights from experiments at the COSY accelerator are also discussed.

Towards the P-wave nucleon-pion scattering amplitude in the $\Delta$ (1232) channel

“…Previous studies of the ∆ coupling to the Nπ channel have used the Michael-McNeile method to determine the coupling [30] as well as the Lüscher method [31,32,33]. None of the previous studies have fully taken into account the partial-wave mixing.…”

Particle-dimer approach for the Roper resonance in a finite volume

“…Finally, we note that no fit to the lattice data and, also, no similar study for the two-particle N π scattering in the ∆ channel (some lattice studies of ∆-resonance can be found in refs. [107][108][109][110][111][112]) are performed in this pioneering study.…”

Jülich-Bonn-Washington model for pion electroproduction multipoles

“…[29] for a recent review. Notably, first calculations of meson-baryon scattering amplitudes in lattice QCD have appeared recently, some of them containing the ∆(1232)3/2 + resonance [30][31][32][33][34]. Complementary to photoproduction reactions, radiative decays of excited baryons, such as measured by CLAS [35], can reveal information about their nature, see, e.g., Refs.…”