Unified resolution of the $R(D)$ and $R(D^{*})$ anomalies and the lepton flavor violating decay $h\to \mu \tau$

Taking advantage of the fact that the flavor of the neutrino in semileptonic $B$ decays $B\to D^{(*)}\tau \nu$ is not known, we show how a minimal set of higher-dimensional lepton flavor violating (LFV) operators can explain the $R(D^{(*)})$ anomalies and, as a spin-off, can give rise to the LFV decay of the Higgs boson, $h\to \mu \tau$. We also show how none but the minimal set of operators survive the present data.

Figure 1

Typical contributions to the decay $h\to {\mu }^{+}{\tau }^{-}$ initiated by the new operators. Diagrams for the conjugate process would be analogous.

Figure 2

Current experimental status in the measurements of $R(D)$ and $R(D^{*})$ [27].

Figure 3

The ${\chi }^2$ contours for Model 1 (left) and Model 2 (right). The $1\sigma$ (68.27%), $2\sigma$ (95.45%), and $4\sigma$ (99.99%) confidence levels are shown by red, orange, and blue lines, respectively.

Figure 4

The $1\sigma$ contour in the $R(D)\text{−}R(D^{*})$ plane with the best fit points for Model 2. The current experimental results and the world average are also shown for comparison.