$${b\rightarrow c\tau \nu }$$ b → c τ ν transitions in the standard model effective field theory

Abstract

The R(D (*)) anomalies observed in B → D (*) τ ν decays have attracted much attention in recent years. In this paper, we study the B → D (*) τ ν, b → c τ ν, B c → (J/ψ, η c)τ ν, B → X c τ ν, and B c → τ ν decays, all being mediated by the same quark-level b → cτ ν transition, in the Standard Model Effective Field Theory. The most relevant dimension-six operators for these processes are Q (3) lq , Q ledq , Q (1) lequ , and Q (3) lequ in the Warsaw basis. Evolution of the corresponding Wilson coefficients from the new physics scale = 1 TeV down to the characteristic scale μ b 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 B(B c → τ ν) 10%, a single C (3) lq 3323 () or C (3) lequ 3332 () can still be used to resolve the R(D (*)) anomalies at 1σ , while a single C (1) lequ 3332 () is already ruled out by the measured R(D (*)) at more than 3σ. By minimizing the χ 2 (C i) function constructed based on the current data on R(D), R(D *), P τ (D *), R(J/ψ), and R(X c), we obtain eleven most trustworthy scenarios, each of which can provide a good explanation of the R(D (*)) anomalies at 1σ. 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.

Global fit to b → cτν transitions

“…Finally, one has to consider the running from Λ EW to Λ NP [60,[117][118][119][120]. The corresponding equations can be solved numerically, but also analytically to very good approximation [121].…”

“…As an illustration of the effect of the running, we show the relation between the WET Wilson coefficients at µ b ≈ 5 GeV and the SMEFT Wilson coefficients at an hypothetical NP scale of Λ = 1 TeV, calculated in Ref. [60,120], which can be trivially inverted:…”

Explaining b→sℓ+ℓ− data by sneutrinos in the R -parity violating MSSM

“…For example, the authors in Ref. [38] attempt to explain b → sμ þ μ − anomaly via one-loop contributions involving right-handed down type squarksd R , which can help solve RðD Ã Þ anomaly at tree level [38,42,[44][45][46][47][48]. However, they note that it is difficult to find a viable explanation due to the severe constraints from the upper limit on the branching fraction of B → K ðÃÞ νν decays.…”

Implication of RD(*) anomalies on semileptonic decays of Σb and Rajeev1, Dutta2, Kumbhakar3 2019Phys. Rev. D15080View full textAdd to dashboardCite

“…SM predictions World averages Deviation RD = B(B → Dτ ν)/B(B → Dlν) 0.299 ± 0.003 [4][5][6][7] 0.340 ± 0.027 ± 0.013 [13][14][15][16] 1.4σ RD * = B(B → D * τ ν)/B(B → D * lν) 0.258 ± 0.005 [8][9][10][11] 0.295 ± 0.011 ± 0.008 [13][14][15][16][17][18][19][20][21][22] 2.5σ The clear disagreements between the SM predictions and the experimental measurements strongly indicate towards possible new physics. Several new physics scenarios are being investigated within model dependent and model independent frameworks [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Similarly, implications of R D ( * ) anomalies on similar decay modes have been studied as well.…”