Probing unknown nonperturbative effects in b → s ℓℓ with inclusive and exclusive observables

@misc{alvarezcartelle2026probing,
  title = {{Probing unknown nonperturbative effects in $b \to s \ell\ell$ with inclusive and exclusive observables}},
  author = {P. Alvarez-Cartelle and B. Capdevila and E. Lunghi and J. Matias},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2605.06567},
  eprint = {2605.06567},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2605.06567},
}

TY  - UNPB
TI  - Probing unknown nonperturbative effects in b → s ℓℓ with inclusive and exclusive observables
AU  - P. Alvarez-Cartelle
AU  - B. Capdevila
AU  - E. Lunghi
AU  - J. Matias
PY  - 2026
DA  - 2026/09/09
PB  - arXiv
DO  - 10.48550/arxiv.2605.06567
UR  - https://arxiv.org/abs/2605.06567
AB  - 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→ 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 cc̅ loops affect inclusive B→ X_s ℓℓ and exclusive B→ K^(*)ℓℓ modes differently. In inclusive decays, factorizable contributions are exactly determined from data on e^+e^-→ 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.
ER  -