Measurement of the D[superscript 0] → π[superscript -]e[superscript +]ν[subscript e] differential decay branching fraction as a function of q[superscript 2] and study of form factor parametrizations

Abstract

Based on a sample of 500 million e[superscript +]e[superscript -] → c[bar over c] events recorded by the BABAR detector at c.m. energies of close to 10.6 GeV, we report on a study of the decay D[superscript 0] → π[superscript -]e[superscript +]ν[subscript e]. We measure the ratio of branching fractions, R[subscript D] = B(D[superscript 0] → π[superscript -]e[superscript +]ν[subscript e])/B(D[superscript 0] → K[superscript -]π[superscript +]) = 0.0713 ± 0.0017[subscript stat] ± 0.0024[subscript syst], and use the present world average for B(D[superscript 0] → K[superscript -]π[superscript +] to obtain B(D[superscript 0] → π[superscript -]e[superscript +]ν[subscript e]) = (2.770 ± 0.068[subscript stat] ± 0.092[subscript syst] ± 0.037[subscript ext]) × 10[superscript -3] where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on q[superscript 2], the four-momentum transfer squared between the D and the π meson, is compared to various theoretical predictions for the hadronic form factor, f[π over +,D](q[superscript 2]), and the normalization |V[subscript cd]| × f[π over +,D](q[superscript 2] = 0) = 0.1374 ± 0.0038[subscript stat] ± 0.0022[subscript syst] ± 0.0009[subscript ext] is extracted from a fit to data. Using the most recent LQCD prediction of f[π over +,D](q[superscript 2] = 0) = 0.666 ± 0.029, we obtain |V[subscript cd]| = 0.206 ± 0.007[subscript exp] ± 0.009[subscript LQCD]. Assuming, instead, |V[subscript cd]| = |V[subscript us]| = 0.2252 ± 0.0009, we obtain f[π over +,D](q[superscript 2] = 0) = 0.610 ± 0.020subscript exp] ± 0.005[subscript ext]. The q[superscript 2] dependence of f[π over +,D](q[superscript 2]) is compared to a variety of multipole parametrizations. This information is applied to B[superscript 0] → π[superscript -]e[superscript +]ν[subscript e] decays and, combined with an earlier B[superscript 0] → π[superscript -]e[superscript +]ν[subscript e] measurement by BABAR, is used to derive estimates of |V[subscript ub]|.