Using data from the FOCUS experiment we analyze the D + π − and D 0 π + invariant mass distributions. We measure the D * 0 2 mass M D * 0 2 = (2464.5 ± 1.1 ± 1.9) MeV/c 2 and width Γ D * 0 2

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Using a large sample of charm semileptonic decays collected by the FOCUS photoproduction experiment at Fermilab, we present evidence for a small, even spinAlthough this interference significantly distorts the D + → K − π + µ + ν decay angular distributions, the new amplitude creates only a very small distortion to the observed kaon pion mass distribution when integrated over the other kinematic variables describing the decay. Our data can be described by K * 0 interference with either a constant amplitude or broad spin zero resonance.

We have performed a search for CPT violation in neutral charm meson oscillations. While flavor mixing in the charm sector is predicted to be small by the Standard Model, it is still possible to investigate CPT violation through a study of the proper time dependence of a CPT asymmetry in right-sign decay rates for D 0 → K − π + and D 0 → K + π − . This asymmetry is related to the CPT violating complex parameter ξ and the mixing parameters x and y: A CP T ∝ Re ξ y − Im ξ x. Our 95% confidence level limit is −0.0068 < Re ξ y − Im ξ x < 0.0234. Within the framework of the Standard Model Extension incorporating general CPT violation, we also find 95% confidence level limits for the expressions involving coefficients of Lorentz violation of (−2.8 < N (x, y, δ)(∆a 0 +0.6 ∆a Z ) < 4.8)×10 −16 GeV, (−7.0 < N (x, y, δ)∆a X < 3.8) × 10 −16 GeV, and (−7.0 < N (x, y, δ)∆a Y < 3.8) × 10 −16 GeV, where N (x, y, δ) is the factor which incorporates mixing parameters x, y and the doubly Cabibbo suppressed to Cabibbo favored relative strong phase δ.