New insights into the spin structure of the nucleon

We analyze the low-energy spin structure of the nucleon in a covariant effective field theory with explicit spin-3/2 degrees of freedom to third order in the small scale expansion. Using the available data on the strong and electromagnetic width of the Delta resonance, we give parameter-free predictions for various spin polarizabilities and moments of spin structure functions. We find an improved description of the nucleon spin structure at finite photon virtualities for some observables and point out the necessity of a fourth-order calculation. DOI: 10.1103/PhysRevD.87.054032