A more subtle improvement in mass resolution is obtained by using the direction vectors obtained from the candidate vertexing algorithm () described above. The standard (or TRACCE) direction vectors for linked tracks are determined solely from the downstream microstrip stations. Using the direction vectors allows us to incorporate Target Silicon information into the direction vectors. This improves the mass resolution by about 1%. A comparison between 's reconstructed with the TRACCE vectors and the vectors is shown in select:dvert_comp.