Study of the decay D+s→K+K−e+νe

Abstract

Using 214 fb − 1 of data recorded by the BABAR detector at the PEPII electron-positron collider, we study the decay D + s → K + K − e + ν e . Except for a small S-wave contribution, the events with K + K − masses in the range 1.01 - 1.03 GeV / c 2 correspond to ϕ mesons. For D + s → ϕ e + ν e decays, we measure the relative normalization of the Lorentz invariant form factors at q 2 = 0 , r V = V ( 0 ) / A 1 ( 0 ) = 1.849 ± 0.060 ± 0.095 , r 2 = A 2 ( 0 ) / A 1 ( 0 ) = 0.763 ± 0.071 ± 0.065 and the pole mass of the axial-vector form factors m A = ( 2.28 + 0.23 − 0.18 ± 0.18 ) GeV / c 2 . Within the same K + K − mass range, we also measure the relative branching fraction B ( D + s → K + K − e + ν e ) / B ( D + s → K + K − π + ) = 0.558 ± 0.007 ± 0.016 , from which we obtain the total branching fraction B ( D + s → ϕ e + ν e ) = ( 2.61 ± 0.03 ± 0.08 ± 0.15 ) × 10 − 2 . By comparing this value with the predicted decay rate, we extract A 1 ( 0 ) = 0.607 ± 0.011 ± 0.019 ± 0.018 . The stated uncertainties are statistical, systematic, and from external inputs.