New physics effect on B c → J / ψ τ ν ˉ in relation to the R D ( ? ) anomaly

摘要

We study possible new physics (NP) effects on B c → J / ψ τ ν ˉ , which has been recently measured at LHCb as the ratio of R J / ψ = B ( B c → J / ψ τ ν ˉ ) / B ( B c → J / ψ μ ν ˉ ) . Combining it with the long-standing R D ( ? ) measurements, in which the discrepancy with the prediction of the standard model is present, we find possible solutions to the anomaly by several NP types. Then, we see that adding the R J / ψ measurement does not improve NP fit to data, but the NP scenarios still give better χ 2 than the SM. We also investigate indirect NP constraints from the lifetime of B c and NP predictions on the τ longitudinal polarization in B ˉ → D ? τ ν ˉ .