Test of lepton flavour universality with B⁰→ K^*0ℓ⁺ℓ^- decays at large dilepton invariant mass

2026/04/09 by LHCb collaboration, R. Aaij, M. Abdelfatah +1115 · 2 voices
Physics and Astronomy · #hep-ex

paper · pdf · doi:10.1103/vzv9-hcks

published as Phys. Rev. Lett. 137 (2026) 051803 · All figures and tables, along with any supplementary material and additional information, are available at https://lhcb-glance.cern.ch/alcm/public/analysis/full-details/5670 (LHCb public pages)

arxiv published 2026/04/09 · arxiv created 2026/07/31 · arxiv updated 2026/07/31

Abstract

Muon-electron universality is tested in B⁰ → K^*0 ℓ⁺ ℓ^- decays, in the dilepton-invariant-mass region above the ψ(2S) resonance. The analysis uses beauty mesons produced in proton-proton collisions recorded by the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb^-1. The ratio of branching fractions between the muon and electron channels R_K^*0 is measured to be 1.08 ^+0.14_-0.12(stat) ± 0.07(syst) for a dilepton-invariant-mass squared above 14.0 GeV²/c⁴, consistent with the standard model prediction. This result represents the most precise measurement of R_K^*0 in this region and the first such measurement performed at a hadron collider.

Citations

• The LHCb Stripping Project: Sustainable Legacy Data Processing for High-Energy Physics
• Measurement of the branching fraction ratio R_K at large dilepton invariant mass
• Test of Lepton Flavor Universality with B + → K + π + π − ℓ + ℓ − Decays
• LHC di-lepton searches for Z^′ bosons which explain measurements of b → s l⁺l^- transitions
• Tests of lepton universality using B⁰→ K⁰_S ℓ⁺ ℓ^- and B⁺→ K^*+ ℓ⁺ ℓ^- decays
• Test of lepton universality in beauty-quark decays
• Electroweak Measurements in Electron-Positron Collisions at W-Boson-Pair Energies at LEP
• Geant4 developments and applications
• Precision Electroweak Measurements on the Z Resonance
• Review of Particle Physics

Discussions

• #LHCbpaper: Test of lepton flavour universality with B⁰ → K*⁰ℓ⁺ℓ⁻ decays at large dilepton invariant mass (arXiv:2604.08631) https://arxiv.org/abs/2604.08631 [bsky, 2 points, 0 comments]
• Test of lepton flavour universality with B⁰→ K*⁰ℓ⁺ℓ⁻ decays at large dilepton invariant mass - The ratio of branching fractions between the muon and electron channels is measured to be 1.08+0.14−0.12( [bsky, 0 points, 0 comments]

Related

• Measurement of the branching fraction ratio R_K at large dilepton invariant mass
• Test of Lepton Flavor Universality with B + → K + π + π − ℓ + ℓ − Decays
• Tests of lepton universality using B⁰→ K⁰_S ℓ⁺ ℓ^- and B⁺→ K^*+ ℓ⁺ ℓ^- decays
• Test of lepton flavour universality in b→ sℓ⁺ℓ^- decays
• Test of Lepton Flavor Universality with B s 0 → ϕ ℓ + ℓ − Decays