A test of lepton flavour universality with a measurement of $R(D^{(*)})$ using semileptonic B tagging and leptonic $\tau$ decays
| Abstract | We report the measurement of the branching fractions $\mathcal{R}(D^{(*)}) = \frac{\mathcal{B}(\overline{B} \to D^{(*)} \tau \bar{\nu}_\tau)}{\mathcal{B}(\overline{B} \to D^{(*)} \ell \bar{\nu}_\ell)}$ with $\ell$ denoting either an electron or a muon. This measurement tests the universality of the charged-current weak interaction and utilises 364fb$^{-1}$ of integrated luminosity of electron-positron collision data collected with the Belle~II detector. Signal candidates are reconstructed in collision events in which one of the $B$ mesons in the $\Upsilon(4S) \to B\overline B$ decay is fully reconstructed in semileptonic modes, and the $\tau$ is reconstructed using leptonic decays. |
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| Tags | Run 1 |
| Working group | Semileptonic and Missing Energy Decay |
| Principal authors | @ Florian Bernlochner, Jochen Dingfelder, Peter Lewis, Alina Manthei, Markus Prim |
| Reference | published in PRD |
| Document | BELLE2-PUB-DRAFT-2024-014 |
| Links | arXiv:2504.11220, Inspire, |