Testing the Standard Model in B → D τ ν decay with minimal theory input

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Recent experimental results for the ratio of the branching fractions of B → D⁽*⁾τντ and B→ D⁽*⁾ μνμ decays came as a surprise and lead to a discussion of possibility to constraining new physics through these modes. Here we focus on Br(B → D τντ)/Br(B → D μνμ) and argue that the result is consistent with the Standard Model within 2σ and that the test of compatibility of this ratio with the Standard Model can be done experimentally with a minimal theory input. We also show that these two decay channels can provide us with quite good constraints of the new physics couplings.