  Beam-helicity asymmetries for the gamma+p -> pi+ + pi- + p reaction have been
measured for center-of-mass energies between 1.35 GeV and 2.30 GeV at Jefferson
Lab with the CEBAF Large Acceptance Spectrometer using circularly polarized
tagged photons. The beam-helicity asymmetries vary with kinematics and exhibit
strong sensitivity to the dynamics of the reaction, as demonstrated in the
comparison of the data with results of various phenomenological model
calculations. These models currently do not provide an adequate description of
the data over the entire kinematic range covered in this experiment. Additional
polarization observables are accessible in an upcoming experiment at Jefferson
Lab with polarized beam and target.
