Probing unknown nonperturbative effects in $b \to s \ell\ell$ with inclusive and exclusive observables
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| Natura: | Preprint |
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2026
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| _version_ | 1866911658231726080 |
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| author | Alvarez-Cartelle, P. Capdevila, B. Lunghi, E. Matias, J. |
| author_facet | Alvarez-Cartelle, P. Capdevila, B. Lunghi, E. Matias, J. |
| contents | In this paper we revisit, from a different perspective, a long-standing question: ``Is the systematic deficit observed in all branching ratios mediated by a $b\to s μμ$ transition due to New Physics, or to a hypothetical constant unknown universal hadronic contribution that mimics New Physics?'' The key observation that allows us to distinguish between these two possibilities is that non-perturbative contributions associated with $c\bar c$ loops affect inclusive $B\to X_s \ell\ell$ and exclusive $B\to K^{(*)}\ell\ell$ modes differently. In inclusive decays, factorizable contributions are exactly determined from data on $e^+e^-\to \mathrm{hadrons}$, while non-factorizable corrections are described by resolved-photon contributions at low $q^2$ and by local power corrections at high $q^2$. In exclusive decays, by contrast, hypothetical charming-penguin effects, beyond those already included in current uncertainty estimates, could appear, in a worst-case scenario, as a constant, universal contribution that it seems, in principle, indistinguishable from genuine New Physics. We identify two observables, constructed from ratios of exclusive to inclusive modes, that can discriminate between a New Physics contribution and a constant hadronic contribution. Moreover, these ratios can be measured directly by LHCb, as they do not require any normalisation to $J/ψK^{(*)}$ branching fractions from B factories. A preliminary evaluation of these observables with present data shows some preference for the New Physics interpretation. In a complementary test, a comparison between inclusive measurements and the corresponding sum of exclusive modes at high $q^2$ similarly disfavours an explanation based on a constant hadronic contribution. Finally, we provide projections for the new observables based on expected LHCb and Belle II measurements in the near future. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_06567 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Probing unknown nonperturbative effects in $b \to s \ell\ell$ with inclusive and exclusive observables Alvarez-Cartelle, P. Capdevila, B. Lunghi, E. Matias, J. High Energy Physics - Phenomenology High Energy Physics - Experiment In this paper we revisit, from a different perspective, a long-standing question: ``Is the systematic deficit observed in all branching ratios mediated by a $b\to s μμ$ transition due to New Physics, or to a hypothetical constant unknown universal hadronic contribution that mimics New Physics?'' The key observation that allows us to distinguish between these two possibilities is that non-perturbative contributions associated with $c\bar c$ loops affect inclusive $B\to X_s \ell\ell$ and exclusive $B\to K^{(*)}\ell\ell$ modes differently. In inclusive decays, factorizable contributions are exactly determined from data on $e^+e^-\to \mathrm{hadrons}$, while non-factorizable corrections are described by resolved-photon contributions at low $q^2$ and by local power corrections at high $q^2$. In exclusive decays, by contrast, hypothetical charming-penguin effects, beyond those already included in current uncertainty estimates, could appear, in a worst-case scenario, as a constant, universal contribution that it seems, in principle, indistinguishable from genuine New Physics. We identify two observables, constructed from ratios of exclusive to inclusive modes, that can discriminate between a New Physics contribution and a constant hadronic contribution. Moreover, these ratios can be measured directly by LHCb, as they do not require any normalisation to $J/ψK^{(*)}$ branching fractions from B factories. A preliminary evaluation of these observables with present data shows some preference for the New Physics interpretation. In a complementary test, a comparison between inclusive measurements and the corresponding sum of exclusive modes at high $q^2$ similarly disfavours an explanation based on a constant hadronic contribution. Finally, we provide projections for the new observables based on expected LHCb and Belle II measurements in the near future. |
| title | Probing unknown nonperturbative effects in $b \to s \ell\ell$ with inclusive and exclusive observables |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2605.06567 |