Abstract:
We report measurements of the ratios of branching fractions for B→Dˉ(∗)πℓ+νℓB→Dˉ(∗)πℓ+νℓ and B→Dˉ(∗)π+π−ℓ+νℓB→Dˉ(∗)π+π−ℓ+νℓ relative to B→Dˉ∗ℓ+νℓB→Dˉ∗ℓ+νℓ decays with ℓ=e,μℓ=e,μ. These results are obtained from a data sample that contains 772×106BBˉ772×106BBˉ pairs collected near the Υ(4S)Υ(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e−e+e− collider. Fully reconstructing both BB mesons in the event, we obtain \begin{align*} \frac{B(B^0 \to \bar{D}^0\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (7.24\pm0.36\pm0.12)\%\ ,\\ \frac{B(B^+ \to D^-\pi^+\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (6.78\pm0.24\pm0.15)\%\ ,\\ \frac{B(B^0 \to \bar{D}^{*0}\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (11.10\pm0.48\pm0.20)\%\ ,\\ \frac{B(B^+ \to D^{*-}\pi^+\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (9.50\pm0.33\pm0.27)\%\ ,\\ \frac{B(B^0 \to D^-\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (2.91\pm0.37\pm0.25)\%\ ,\\ \frac{B(B^+ \to \bar{D}^0\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (3.10\pm0.26\pm0.21)\%\ ,\\ \frac{B(B^0 \to D^{*-}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (1.03\pm0.43\pm0.18)\%\ ,\\ \frac{B(B^+ \to \bar{D}^{*0}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (1.25\pm0.27\pm0.15)\%\ , \end{align*} where the uncertainties are statistical and systematic, respectively. The invariant mass spectra of the DπDπ, D∗πD∗π, and DππDππ systems are studied. Branching fraction products are extracted, among them the first observations of B(B0→D1−ℓ+νℓ)×B(D1−→D−π+π−)=(0.102±0.013±0.009)%B(B0→D1−ℓ+νℓ)×B(D1−→D−π+π−)=(0.102±0.013±0.009)% and B(B+→Dˉ10ℓ+νℓ)×B(Dˉ10→Dˉ0π+π−)=(0.105±0.011±0.008)%B(B+→Dˉ10ℓ+νℓ)×B(Dˉ10→Dˉ0π+π−)=(0.105±0.011±0.008)%.
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