Measuring $A_\text{FB}^b$ and $R_b$ with exclusive $b$-hadron decays at the FCC-ee
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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915458720989184 |
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| author | Röhrig, Lars Kröninger, Kevin Madar, Romain Monteil, Stéphane Palla, Fabrizio Perez, Emmanuel |
| author_facet | Röhrig, Lars Kröninger, Kevin Madar, Romain Monteil, Stéphane Palla, Fabrizio Perez, Emmanuel |
| contents | This paper presents a novel tagging technique to measure the beauty-quark partial decay-width ratio $R_b$ and its forward-backward asymmetry $A_\text{FB}^b$ at the FCC-ee, using $\mathcal{O}(10^{12})$ $Z$-boson decays. The method is based on the exclusive reconstruction of a selected list of $b$-hadron decay modes in $Z\to b\bar{b}$ events at the $Z$ pole, which can provide the flavour and possibly the charge of the hemisphere. This approach effectively eliminates the contamination from light-quark physics events and reduces the leading systematic uncertainties arising from background contamination, tagging-efficiency correlations, and gluon-radiation corrections by exploiting the geometric and kinematic properties of beauty hadrons. This results in a total relative uncertainty of the order of $0.01\,\%$ for both observables. Furthermore, this precision allows to obtain a commensurate precision on the weak mixing angle $\sin^2(θ_W^\text{eff})$ compared to the muon forward-backward asymmetry on the order of $0.002\,\%$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2502_17281 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Measuring $A_\text{FB}^b$ and $R_b$ with exclusive $b$-hadron decays at the FCC-ee Röhrig, Lars Kröninger, Kevin Madar, Romain Monteil, Stéphane Palla, Fabrizio Perez, Emmanuel High Energy Physics - Experiment High Energy Physics - Phenomenology This paper presents a novel tagging technique to measure the beauty-quark partial decay-width ratio $R_b$ and its forward-backward asymmetry $A_\text{FB}^b$ at the FCC-ee, using $\mathcal{O}(10^{12})$ $Z$-boson decays. The method is based on the exclusive reconstruction of a selected list of $b$-hadron decay modes in $Z\to b\bar{b}$ events at the $Z$ pole, which can provide the flavour and possibly the charge of the hemisphere. This approach effectively eliminates the contamination from light-quark physics events and reduces the leading systematic uncertainties arising from background contamination, tagging-efficiency correlations, and gluon-radiation corrections by exploiting the geometric and kinematic properties of beauty hadrons. This results in a total relative uncertainty of the order of $0.01\,\%$ for both observables. Furthermore, this precision allows to obtain a commensurate precision on the weak mixing angle $\sin^2(θ_W^\text{eff})$ compared to the muon forward-backward asymmetry on the order of $0.002\,\%$. |
| title | Measuring $A_\text{FB}^b$ and $R_b$ with exclusive $b$-hadron decays at the FCC-ee |
| topic | High Energy Physics - Experiment High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2502.17281 |