First Measurement of $Γ(D*+)$

Abstract

We present the first measurement of the D*+ width using 9/fb of e+e- data collected near the Upsilon(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*+ -> D0 pi+ decay. We find the D*+ width equals 96+/-4(Statistical)+/-22(Systematic) keV. We also measure the energy release in the decay and compute m(D*+)-m(D0) = 145.412+/-0.002(Statistical)+/-0.012(Systematic) MeV/c**2.