Semileptonic $B_c\to \hat{I}{\cdot }_c,J/\ddot{I}ˆ$ transitions

Abstract

Using a systematic, symmetry-preserving continuum approach to the Standard Model strong-interaction bound-state problem, we deliver parameter-free predictions for all semileptonic $B_c\to \hat{I}{\cdot }_c,J/\ddot{I}ˆ$ transition form factors on the complete domains of empirically accessible momentum transfers. Working with branching fractions calculated therefrom, the following values of the ratios for $\ddot{I}„$ over $\hat{I}¼$ final states are obtained: $R_{\hat{I}{\cdot }_c}=0.313(22)$ and $R_{J/\ddot{I}ˆ}=0.242(47)$. Combined with other recent results, our analysis confirms a $2\ddot{I}ƒ$ discrepancy between the Standard Model prediction for $R_{J/\ddot{I}ˆ}$ and the single available experimental result.

8 pages, 4 figures, 5 tables