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| Main Authors: | , , |
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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2503.22635 |
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| _version_ | 1866917109102018560 |
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| author | Bordone, Marzia Cornella, Claudia Davighi, Joe |
| author_facet | Bordone, Marzia Cornella, Claudia Davighi, Joe |
| contents | The rare semi-leptonic decays $B\to K^\ast \ell^+\ell^-$, with $\ell=e, μ$, are highly sensitive to new physics (NP) due to their suppression in the Standard Model (SM). Current LHCb measurements in the muon channel exhibit a significant tension with state-of-the-art SM theory predictions. The proposed tera-$Z$ run at FCC-ee provides a unique opportunity to untangle the origin of this tension by producing a very large sample of $B$-mesons in a clean $e^+e^-$ environment. We explore the expected precision of $B\to K^\ast \ell^+\ell^-$ ($\ell=e, μ$) measurements at FCC-ee, complementing existing studies with $τ^+τ^-$ in the final state, and compare with HL-LHC projections. For the case of muons in the final state, we show that HL-LHC and FCC-ee are expected to deliver a similar number of events, while the latter performs much better in the case of final state electrons. Regardless of the lepton flavour, we expect the FCC-ee environment to be much cleaner than at HL-LHC, with subleading systematics. We also find that a significant reduction in theory uncertainties on the SM predictions is required to capitalize on the advantage going from HL-LHC to FCC-ee. We demonstrate the power of such measurements at FCC-ee to extract information on the long-distance contribution to these decays, and to reveal evidence for new physics even if no deviations are seen in electroweak precision tests. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_22635 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Precision Tests in $b\to s\ell^+\ell^-$ ($\ell=e,μ$) at FCC-ee Bordone, Marzia Cornella, Claudia Davighi, Joe High Energy Physics - Phenomenology The rare semi-leptonic decays $B\to K^\ast \ell^+\ell^-$, with $\ell=e, μ$, are highly sensitive to new physics (NP) due to their suppression in the Standard Model (SM). Current LHCb measurements in the muon channel exhibit a significant tension with state-of-the-art SM theory predictions. The proposed tera-$Z$ run at FCC-ee provides a unique opportunity to untangle the origin of this tension by producing a very large sample of $B$-mesons in a clean $e^+e^-$ environment. We explore the expected precision of $B\to K^\ast \ell^+\ell^-$ ($\ell=e, μ$) measurements at FCC-ee, complementing existing studies with $τ^+τ^-$ in the final state, and compare with HL-LHC projections. For the case of muons in the final state, we show that HL-LHC and FCC-ee are expected to deliver a similar number of events, while the latter performs much better in the case of final state electrons. Regardless of the lepton flavour, we expect the FCC-ee environment to be much cleaner than at HL-LHC, with subleading systematics. We also find that a significant reduction in theory uncertainties on the SM predictions is required to capitalize on the advantage going from HL-LHC to FCC-ee. We demonstrate the power of such measurements at FCC-ee to extract information on the long-distance contribution to these decays, and to reveal evidence for new physics even if no deviations are seen in electroweak precision tests. |
| title | Precision Tests in $b\to s\ell^+\ell^-$ ($\ell=e,μ$) at FCC-ee |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2503.22635 |