Methods for optical calibration of the BigBite hadron spectrometer

The techniques for the optical calibration of Jefferson Lab's large-acceptance magnetic hadron spectrometer, BigBite, have been examined. The most consistent and stable results were obtained using a method based on singular value decomposition. In spite of the complexity of the optics, the particles' positions and momenta at the target have been precisely reconstructed from the coordinates measured in the detectors by means of a single back-tracing matrix. The technique is applicable to any similar magnetic spectrometer and any particle type. For 0.55 GeV/c protons, we have established a vertex resolution of 1.2 cm, angular resolutions of 7 mrad and 13 mrad (in-plane and out-of-plane, respectively), and a relative momentum resolution of 1.6%.