| V_{u b} | and B → η^(′) form factors in covariant light-front approach

B → (π, η, η^′) transition form factors are investigated in the covariant light-front approach. With theoretical uncertainties, we find that B → (π, η, η^′) form factors at q² = 0 are f₊^{(π, η, η′)} (0) = (0.245_{- 0.001}^{+ 0.000} ± 0.011, 0.220 ± 0.009 ± 0.009, 0.180 ± 0.008_{- 0.007}^{+ 0.008}) for vector current and f_T^{(π, η, η′)} (0) = (0.239_{- 0.003 - 0.018}^{+ 0.002 + 0.020}, 0.211 ± 0.009_{- 0.015}^{+ 0.017}, 0.173 ± 0.007_{- 0.013}^{+ 0.014}) for tensor current, respectively. With the obtained q²-dependent f₊^π (q²) and observed branching ratio (BR) for over(B, ̄)_d → π⁺ ℓ over(ν, ̄)_ℓ, the V_{u b} is found as | V_{u b} |_{L F} = (3.99 ± 0.13) × 10^{- 3}. As a result, the predicted BRs for over(B, ̄) → (η, η^′) ℓ over(ν, ̄)_ℓ decays with ℓ = e, μ are given by (0.49_{- 0.04 - 0.07}^{+ 0.02 + 0.10}, 0.24_{- 0.02 - 0.03}^{+ 0.01 + 0.04}) × 10^{- 4}, while the BRs for D^- → (η, η^′) ℓ over(ν, ̄)_ℓ are (11.1_{- 0.6 - 0.9}^{+ 0.5 + 0.9}, 1.79_{- 0.08 - 0.12}^{+ 0.07 + 0.12}) × 10^{- 4}. In addition, we also study the integrated lepton angular asymmetries for over(B, ̄) → (π, η, η^′) τ over(ν, ̄)_τ: (0.277_{- 0.001 - 0.007}^{+ 0.001 + 0.005}, 0.290_{- 0.000 - 0.003}^{+ 0.002 + 0.003}, 0.312_{- 0.000 - 0.006}^{+ 0.004 + 0.005}).