First measurement of Γ(D*+) and precision measurement of mD*+-mD0

We present the first measurement of the D^*+ width using 9/fb of e⁺e^- data collected near the Υ(4S) resonance by the CLEO II.V detector. Our method uses advanced tracking techniques and a reconstruction method that takes advantage of the small vertical size of the CESR beam spot to measure the energy release distribution from the D^*+-->D⁰π⁺ decay. We find Γ(D^*+)=96+/-4 (statistical)+/-22 (systematic) keV. We also measure the energy release in the decay and compute Δm≡m_D^*+-m_D⁰=145.412+/-0.002 (statistical)+/-0.012 (systematic) MeV/c².