Analyzing power in pion-proton bremsstrahlung, and the Delta ++(1232) magnetic moment

Magnetic moment of the delta(1232) resonance in chiral effective-field theory

We perform a relativistic chiral effective-field theory calculation of the radiative pion photoproduction (gammap--> pi(0)pgamma(')) in the Delta-resonance region, to next-to-leading order in the "delta expansion." This work is aimed at a model-independent extraction of the Delta(+) magnetic moment from new precise measurements of this reaction. It also predicts the chiral behavior of Delta's magnetic moment, which can be used to extrapolate the recent lattice QCD results to the physical point.

The reaction gammap-->pi0gamma'p and the magnetic dipole moment of the Delta+ 1232 resonance

The reaction gammap-->pi(0)gamma'p has been measured with the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI for energies between sqrt[s]=1221-1331 MeV. The cross section's differential in angle and energy have been determined for the photon gamma' in three bins of the excitation energy. This reaction channel provides access to the magnetic dipole moment of the Delta(+)(1232) resonance and, for the first time, a value of mu(Delta(+))=[2.7(+1.0)(-1.3)(stat)+/-1.5(syst)+/-3(theor)]mu(N) has been extracted.