Magnetic dipole moment of the S11(1535) from the \gamma p \to \gamma   \eta p reaction
  The \gamma p \to \gamma \eta p reaction in the S11(1535) resonance region is investigated as a method to access the S11(1535) magnetic dipole moment. To study the feasibility, we perform calculations of the \gamma p \to \gamma \eta p process within an effective Lagrangian approach containing both the S11 resonant mechanism and a background of non-resonant contributions. Predictions are made for the forthcoming experiments. In particular, we focus on the sensitivity of cross sections and photon asymmetries to the S11(1535) magnetic dipole moment. 
Wen-Tai Chiang, Shin Nan Yang, Marc Vanderhaeghen, Dieter Drechsel