Measurement of the mass difference m(D(s)(+))-m(D(+)) at CDF II

We present a measurement of the mass difference m(D(s)(+))-m(D(+)), where both the D(s)(+) and D(+) are reconstructed in the phipi(+) decay channel. This measurement uses 11.6 pb(-1) of data collected by CDF II using the new displaced-track trigger. The mass difference is found to be m(D(s)(+))-m(D(+))=99.41+/-0.38(stat)+/-0.21(syst) MeV/c(2).