Tracking

The performance of a tracking system may be quantified in terms of its resolution in momentum, angle, impact parameter, and vertexing. The present CLEO II tracking system has demonstrated that it meets all the requirements in these variables to study the physics we anticipate at high luminosity. We have therefore defined this as the minimum goal for the CLEO III tracking system. This is challenging since the tracking length in CLEO III will be shorter than in CLEO II. Consider the charged particle momentum resolution which is given by:

where is the magnetic field strength (Tesla), is the number of measurements along the track, is the projected track length onto the bending plane (m), is the radiation length of the scattering medium (m), is the average space point resolution (m), is v/c, and is the dip angle. The first term in the resolution formula is due to tracking variables, namely resolution, track length and number of measurements. The second term is the contribution due to multiple scattering. Thus, to maintain a fixed momentum resolution as is reduced requires that must be increased correspondingly. Similar arguments hold for other parameters. Therefore, the general philosophy of the CLEO III design is to reduce the tracking length of the drift chamber to provide space for particle identification while maintaining the performance by simultaneously reducing the amount of material in that tracking length.