General broken lines as advanced track fitting method

In HEP experiments the description of the trajectory of a charged particle is obtained from a fit to measurements in tracking detectors. The parametrization of the trajectory has to account for bending in the magnetic field, energy loss and multiple scattering in the detector material. General broken lines implement a track model with proper description of multiple scattering leading to linear equations with a special structure of the corresponding matrix allowing for a fast solution with the computing time depending linearly on the number of measurements. The calculation of the full covariance matrix along the trajectory enables the application to track based alignment and calibration of large detectors with global methods. (orig.)