A sum rule among LFU ratios R^{mu e} for c to d l nu decays holds within 1% under current NP bounds, yielding a prediction for the unmeasured R_n^{mu e} in Lambda_c to n l nu.
$b \to c$ semileptonic sum rule: orbitally excited hadrons
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abstract
We study semileptonic sum rules for $b \to c \tau \overline{\nu}$ transitions involving orbitally excited charm hadrons. Starting from the amplitude-level relation implied by the heavy quark symmetry, we construct sum rules relating these decays. We then examine deviations from the small-velocity limit. Our numerical analysis shows that the deviations generally increase once excited hadrons are involved, with tensor contributions often inducing sizable effects. At present, however, the relevant form factors are not yet sufficiently constrained. Further improvements in the hadronic inputs are essential for these sum rules to yield robust predictions for the corresponding lepton-universality ratios.
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hep-ph 2years
2026 2verdicts
UNVERDICTED 2roles
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The SU(3) flavor symmetry violation in the extended b to c semileptonic sum rule is smaller than expected future experimental uncertainties, supporting new physics-agnostic consistency checks.
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Semileptonic sum rules in heavy-to-light charm decays
A sum rule among LFU ratios R^{mu e} for c to d l nu decays holds within 1% under current NP bounds, yielding a prediction for the unmeasured R_n^{mu e} in Lambda_c to n l nu.
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$b \to c$ semileptonic sum rule: SU(3)$_{\rm{F}}$ symmetry violation
The SU(3) flavor symmetry violation in the extended b to c semileptonic sum rule is smaller than expected future experimental uncertainties, supporting new physics-agnostic consistency checks.