Joint LHCb--Belle II Prospects to Constrain New Physics in $B\to D^{(*)}τν$
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| Format: | Preprint |
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2026
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| _version_ | 1866912995189194752 |
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| author | Albrecht, Johannes Bernlochner, Florian Colonna, Marco Gärtner, Lorenz Mathad, Abhijit Mitreska, Biljana Prim, Markus Tsaklidis, Ilias |
| author_facet | Albrecht, Johannes Bernlochner, Florian Colonna, Marco Gärtner, Lorenz Mathad, Abhijit Mitreska, Biljana Prim, Markus Tsaklidis, Ilias |
| contents | Semileptonic $b\to cτ\barν_τ$ decays are powerful probes of non-Standard-Model effects within an effective-field-theory (EFT) framework, but fully exploiting them in current and future data demands combinations that maximise sensitivity while controlling biases from Standard-Model-based modelling and from theory inputs that are shared, and therefore correlated, across analyses in different experiments. We present a first sensitivity study of a combined extraction of Wilson coefficients in $\bar{B}\to D^{(*)}τ\barν_τ$ decays using LHCb- and Belle~II-like analysis configurations. Detector simulations for signal and backgrounds are typically generated under Standard Model assumptions; if non-SM contributions are present, this can bias the fitted Wilson coefficients. In addition, hadronic inputs such as form-factor parameters of signal and background components are common across analyses, requiring a consistent treatment of fully correlated effects in combinations. To avoid repeating large-scale detector simulation for each EFT hypothesis, we use event-by-event reweighting to map simulated samples to arbitrary combinations of Wilson coefficients. We then compare a simultaneous fit across multiple $\bar{B}\to D^{(*)}τ\barν_τ$ channels and datasets with a combination based on post-fit averages. Sharing Wilson coefficients and common form-factor parameters in the simultaneous fit reduces model-induced biases and improves sensitivity relative to independent fits, providing a robust and scalable strategy for precision EFT constraints in $b\to cτ\barν_τ$ transitions using forthcoming LHCb and Belle~II datasets. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2604_00735 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Joint LHCb--Belle II Prospects to Constrain New Physics in $B\to D^{(*)}τν$ Albrecht, Johannes Bernlochner, Florian Colonna, Marco Gärtner, Lorenz Mathad, Abhijit Mitreska, Biljana Prim, Markus Tsaklidis, Ilias High Energy Physics - Experiment Semileptonic $b\to cτ\barν_τ$ decays are powerful probes of non-Standard-Model effects within an effective-field-theory (EFT) framework, but fully exploiting them in current and future data demands combinations that maximise sensitivity while controlling biases from Standard-Model-based modelling and from theory inputs that are shared, and therefore correlated, across analyses in different experiments. We present a first sensitivity study of a combined extraction of Wilson coefficients in $\bar{B}\to D^{(*)}τ\barν_τ$ decays using LHCb- and Belle~II-like analysis configurations. Detector simulations for signal and backgrounds are typically generated under Standard Model assumptions; if non-SM contributions are present, this can bias the fitted Wilson coefficients. In addition, hadronic inputs such as form-factor parameters of signal and background components are common across analyses, requiring a consistent treatment of fully correlated effects in combinations. To avoid repeating large-scale detector simulation for each EFT hypothesis, we use event-by-event reweighting to map simulated samples to arbitrary combinations of Wilson coefficients. We then compare a simultaneous fit across multiple $\bar{B}\to D^{(*)}τ\barν_τ$ channels and datasets with a combination based on post-fit averages. Sharing Wilson coefficients and common form-factor parameters in the simultaneous fit reduces model-induced biases and improves sensitivity relative to independent fits, providing a robust and scalable strategy for precision EFT constraints in $b\to cτ\barν_τ$ transitions using forthcoming LHCb and Belle~II datasets. |
| title | Joint LHCb--Belle II Prospects to Constrain New Physics in $B\to D^{(*)}τν$ |
| topic | High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2604.00735 |