Analysis of B_c → τν_τ at CEPC
Precise determination of the B_c →τν_τ branching ratio provides an advantageous opportunity for understanding the electroweak structure of the Standard Model, measuring the CKM matrix element |V_(cb)|, and probing new physics models. In this paper, we discuss the potential of measuring the process B_c →τν_τ with τ decaying leptonically at the proposed Circular Electron Positron Collider(CEPC). We conclude that during the Z pole operation, the channel signal can achieve five-σ significance with～10~9 Z decays, and the signal strength accuracies for B_c →τν_τ can reach around 1% level at the nominal CEPC Z pole statistics of one trillion Z decays, assuming the total B_c →τν_τ yield is 3.6 × 10~6. Our theoretical analysis indicates the accuracy could provide a strong constraint on the general effective Hamiltonian for the b → cτν transition. If the total B_c yield can be determined to O(1%)level of accuracy in the future, these results also imply |V_(cb)| could be measured up to O(1%) level of accuracy.