Measurement of the charged and neutral D meson lifetimes

In an exposure of the SLAC Hybrid Facility (SHF) to a backward scattered laser beam, 136 charm events produced in ..gamma..p interactions at 20 GeV have been observed. The SHF 1 m bubble chamber was equipped with a High Resolution Optics camera in order to detect directly the production and decay of charm particles. After imposing rigorous cuts, 48 charged, 50 neutral, and 2 topologically ambiguous decays remain. Using a novel method for estimating the momentum of unconstrained decays, the D meson lifetimes from this sample are measured to be tau/sub D sup +-/ = (8.6 +- 1.3/sub -0.3//sup +0.8/) x 10/sup -13/ sec and tau/sub D/sup 0// = (6.1 +- 0.9 +- 0.3) x 10/sup -13/ sec with a ratio of R = tau/sub D sup +-//tau/sub D/sup 0// = (1.4 +- 0.3/sub -0.1//sup +0.2/). This value of R indicates the Spectator Model charm particle decay mechanism is the dominate piece in the D/sub +-/ and D/sup 0/ decay rates. Limits are placed on additional contributions to the D decay rates from other processes including W-Exchange, Final State Interactions, and Pauli Principle Interference. 34 refs., 41 figs.