Paper detail

Measurement of the Ratio of the Vector to Pseudoscalar Charm Semileptonic Decay Rate Γ(D+ > ANTI-K*0 mu+ nu)/Γ(D+ > ANTI-K0 mu+ nu)

Using a high statistics sample of photo-produced charm particles from the FOCUS experiment at Fermilab, we report on the measurement of the ratio of semileptonic rates Γ(D+ > ANTI-K pi mu+ nu)/Γ(D+ > ANTI-K0 mu+ nu)= 0.625 +/- 0.045 +/- 0.034. Allowing for the K pi S-wave interference measured previously by FOCUS, we extract the vector to pseudoscalar ratio Γ(D+ > ANTI-K*0 mu+ nu)/Γ(D+ > ANTI-K0 mu+ nu)= 0.594 +/- 0.043 +/- 0.033 and the ratio Γ(D+ > ANTI-K0 mu+ nu)/Γ(D+ > K- pi+ pi+)= 1.019 +/- 0.076 +/- 0.065. Our results show a lower ratio for Γ(D > K* \ell nu})/Γ(D > K \ell nu) than has been reported recently and indicate the current world average branching fractions for the decays D+ >ANTI-K0(mu+, e+) nu are low. Using the PDG world average for B(D+ > K- pi+ pi+) we extract B(D+ > ANIT-K0 mu+ nu)=(9.27 +/- 0.69 +/- 0.59 +/- 0.61)%.