$B$ anomalies and the tauphilic leptoquark model

Abstract

We suggest three scalar leptoquarks, $S_1$, ${\tilde R}_2$, and $S_3$ which couple exclusively to the 3rd generation of leptons to explain the $B$ anomalies. The scalar singlet $S_1$ can explain $R(D^{(*)})$, while the doublet ${\tilde R}_2$ is needed to fit the branching ratio ${\rm Br}(B\to K^{(*)}\nu{\bar\nu})$ via the right-handed Wilson coefficients $C_R^\nu$. A strong constraint from $\Delta m_{B_s}$ requires triplet $S_3$ where the mixing term between $S_1$ and $S_3$ is important. Our analysis suggests subdominant $C_{V_L}<0$ and dominant $C_{S_L} >0$ and lepton-flavor universality violating $C_9^{\rm LQ} \approx +1$. The masses are expected to be $M_{S_1}\sim M_{{\tilde R}_2} < M_{S_3} \lesssim 3$ TeV, which can be probed in future colliders.