The "time-track complementarity" approach in the EAS-TOP experiment.

The combined use of muon production height along the shower axis evaluated from muon direction and from muon arrival time selects high energy muons ne ither significantly scattered in the atmosphere nor deviated in the geomagn etic field. This allows the reconstruction of Extensive Air Shower (EAS) lo ngitudinal development in the knee energy region, which provides informatio ns about the nature of primary particle and its interaction with the air nu clei. We describe the possibility to reconstruct the muon height of product ion by the combination of tracking and timing measurements as provided by a large area tracking and timing telescope now available in the EAS-TOP expe riment. 40 m(2) of bakelite RPCs have been installed under the existing muo n-hadron detector in order to obtain accurate measurement of muon arrival t ime with respect to the arrival of the shower core.