A test of lepton universality between muons and electrons is performed using B+ → K+ℓ+ℓ− decays (where ℓ = e, μ), in the dilepton invariant-mass-squared region above 14.3 GeV2/c4. The data used for the measurement consists of beauty meson decays produced in proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1, collected by the LHCb experiment between 2011 and 2018. The ratio of branching fractions for B+→ K+μ+μ− and B+→ K+e+e− decays is measured to be RK=1.08−0.09+0.11stat−0.04+0.04syst, which is consistent with the Standard Model prediction of unity. This constitutes the most precise test of lepton flavour universality using B+ → K+ℓ+ℓ− decays with dilepton invariant-mass-squared above the ψ(2S) mass, whilst being the first of its kind at a hadron collider.

Aaij, R., Abdelmotteleb, A., Abellan Beteta, C., Abudinen, F., Ackernley, T., Adefisoye, A., et al. (2025). Measurement of the branching fraction ratio RK at large dilepton invariant mass. JOURNAL OF HIGH ENERGY PHYSICS, 2025(7) [10.1007/JHEP07(2025)198].

Measurement of the branching fraction ratio RK at large dilepton invariant mass

Anelli A.;Borsato M.;Calvi M.;Capelli S.;Carniti P.;Fazzini D.;Garcia Pardinas J.;Kirsebom V. S.;Malentacca L.;Martinazzoli L.;Martinelli M.;Minotti A.;Pizzichemi M.;Salomoni M.;
2025

Abstract

A test of lepton universality between muons and electrons is performed using B+ → K+ℓ+ℓ− decays (where ℓ = e, μ), in the dilepton invariant-mass-squared region above 14.3 GeV2/c4. The data used for the measurement consists of beauty meson decays produced in proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1, collected by the LHCb experiment between 2011 and 2018. The ratio of branching fractions for B+→ K+μ+μ− and B+→ K+e+e− decays is measured to be RK=1.08−0.09+0.11stat−0.04+0.04syst, which is consistent with the Standard Model prediction of unity. This constitutes the most precise test of lepton flavour universality using B+ → K+ℓ+ℓ− decays with dilepton invariant-mass-squared above the ψ(2S) mass, whilst being the first of its kind at a hadron collider.
Articolo in rivista - Articolo scientifico
B Physics; Flavour Changing Neutral Currents; Flavour Physics; Hadron-Hadron Scattering;
English
17-lug-2025
2025
2025
7
198
none
Aaij, R., Abdelmotteleb, A., Abellan Beteta, C., Abudinen, F., Ackernley, T., Adefisoye, A., et al. (2025). Measurement of the branching fraction ratio RK at large dilepton invariant mass. JOURNAL OF HIGH ENERGY PHYSICS, 2025(7) [10.1007/JHEP07(2025)198].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/578791
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