Abstract
The R(D^{(*)}) anomalies observed in Brightarrow D^{(*)}tau nu decays have attracted much attention in recent years. In this paper, we study the Brightarrow D^{(*)}tau nu , Lambda _brightarrow Lambda _ctau nu , B_crightarrow (J/psi ,,eta _c)tau nu , Brightarrow X_ctau nu , and B_crightarrow tau nu decays, all being mediated by the same quark-level brightarrow ctau nu transition, in the Standard Model Effective Field Theory. The most relevant dimension-six operators for these processes are Q_{lq}^{(3)}, Q_{ledq}, Q^{(1)}_{lequ}, and Q^{(3)}_{lequ} in the Warsaw basis. Evolution of the corresponding Wilson coefficients from the new physics scale Lambda =1 TeV down to the characteristic scale mu _bsimeq m_b is performed at three-loop in QCD and one-loop in EW/QED. It is found that, after taking into account the constraint {{mathcal {B}}}(B_crightarrow tau nu )lesssim 10%, a single left[ C_{lq}^{(3)}right] _{3323}(Lambda ) or left[ C^{(3)}_{lequ}right] _{3332}(Lambda ) can still be used to resolve the R(D^{(*)}) anomalies at 1sigma , while a single left[ C^{(1)}_{lequ}right] _{3332}(Lambda ) is already ruled out by the measured R(D^{(*)}) at more than 3sigma . By minimizing the chi ^2(C_i) function constructed based on the current data on R(D), R(D^*), P_tau (D^*), R(J/psi ), and R(X_c), we obtain eleven most trustworthy scenarios, each of which can provide a good explanation of the R(D^{(*)}) anomalies at 1sigma . To further discriminate these different scenarios, we predict thirty-one observables associated with the processes considered under each NP scenario. It is found that most of the scenarios can be differentiated from each other by using these observables and their correlations.
Highlights
R ( D (∗) ) = B(B B(B → → D(∗)τ D(∗) ν) ν) (1.1)have been measured by the BaBar [4,5] and Belle [6,7,8,9] collaborations with = e, μ, as well as the LHCb [10,11,12] experiment with = μ
In this paper, following this procedure and motivated by the R(D(∗)) anomalies, we shall study the B → D(∗)τ ν, b → cτ ν, Bc → (J/ψ, ηc)τ ν, B → Xcτ ν, as well as Bc → τ ν decays, all being mediated by the same quark-level b → cτ ν transition, in the Standard Model Effective Field Theory (SMEFT) formalism
We have discussed the B → D(∗)τ ν, b → cτ ν, Bc → (J/ψ, ηc)τ ν, B → Xcτ ν, and Bc → τ ν decays, all being mediated by the same quark-level b → cτ ν transition, in the SMEFT framework
Summary
One can see that the difference between experiment and theory is at about 3.78σ corresponding to 99.98% confidence level (C.L.), implying intriguing hints of leptonflavour universality violating new physics (NP) beyond the SM To understand these anomalies, many studies have been done; see for instance Ref. The resulting EFT includes only the QCD and QED gauge interactions coupled to all the six leptons and the five lightest quarks, plus a full set of dimension-six local operators built with these matter fields as well as the gluon and photon field-strength tensors, and is conventionally called the weak effective theory (WET) [75,76,77]. A complete and non-redundant set of dimension-six operators relevant for B physics, together with the complete one-loop anomalous dimensions in QCD and QED, can be found in Refs. Explicit expressions of the helicity amplitudes for b → cτ ν decay are collected in the “Appendix”
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