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

초록

We investigate the transition form factors f(+)(q(2)) and f(-)(q(2)) [or f(0)(q(2))] for the exclusive semileptonic B -> Dl nu(l) (l = e, mu, tau) decays in the standard light-front quark model based on the light-front quantization. The common belief is that while f(+)(q(2)) can be obtained without involving any treacherous contributions such as the zero mode and the instantaneous contribution, f(-)(q(2)) receives those treacherous contributions since it involves at least two components of the current, e.g., (J(+), J(-)) or (J(+), J(perpendicular to)). Contrary to the common belief, we show in the Drell-Yan (q(+) = 0) frame that f(-)(q(2)) obtained from (J(+), J(perpendicular to)) gives identical result to f(-)(q(2)) obtained from (J(+), J(perpendicular to)) 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 -> Dl nu(l) (l = e, mu, tau) and compare with the experimental data as well as other theoretical model predictions. Our results for Br(B -> Dl nu(l)) show reasonable agreement with the experimental data except for the semitauonic B-0 -> D-tau nu(tau), decay. The ratio R(D) = Br(B -> D tau nu(tau))/Br(B -> Dl'nu(l')) (l' = e, mu) is also estimated and compared with the experimental data as well as other theoretical predictions.

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