Hadronic Mass Spectrum Analysis of D+ into K- pi+ mu+ nu Decay and   Measurement of the K*(892)^0 Mass and Width
  We present a Kpi mass spectrum analysis of the four-body semileptonic charm decay D+ into K- pi+ mu+ nu in the range of 0.65 GeV < mKpi < 1.5 GeV. We observe a non-resonant contribution of 5.30 +- 0.74 +0.99 -0.51 % with respect to the total D+ into K- pi+ mu+ nu decay. For the K*(892)^0 resonance, we obtain a mass of 895.41 +- 0.32 +0.35 -0.36 MeV, a width of 47.79 +- 0.86 +1.3 -1.1 MeV, and a Blatt-Weisskopf damping factor parameter of 3.96 +- 0.54 +0.72 -0.90 GeV^(-1). We also report 90 % CL upper limits of 4 % and 0.64 % for the branching ratios of D+ into K*(1680)^0 mu+ nu with respect to D+ into K- pi+ mu+ nu and D+ into K*(1430)^0 mu+ nu with respect to D+ into K- pi+ mu+ nu, respectively. 
FOCUS Collaboration: J. M. Link, et al