Self-consistent light-front quark model analysis of B →dν transition form factors

We investigate the transition form factors f+(q2) and f-(q2) [or f0(q2)] for the exclusive semileptonic B→Dν (=e, μ, τ) decays in the standard light-front quark model based on the light-front quantization. The common belief is that while f+(q2) can be obtained without involving any treacherous contributions such as the zero mode and the instantaneous contribution, f-(q2) receives those treacherous contributions since it involves at least two components of the current, e.g., (J+,J-) or (J+,J). Contrary to the common belief, we show in the Drell-Yan (q+=0) frame that f-(q2) obtained from (J+,J-) gives identical result to f-(q2) obtained from (J+,J) without involving such treacherous contributions in the standard light-front quark model. In our numerical calculations, we obtain the form factors and branching ratios for B→Dν (=e, μ, τ) and compare with the experimental data as well as other theoretical model predictions. Our results for Br(B→Dν) show reasonable agreement with the experimental data except for the semitauonic B0→D-τντ decay. The ratio (D)=Br(B→Dτντ)Br(B→D′ν′) (′=e, μ) is also estimated and compared with the experimental data as well as other theoretical predictions.