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. [The LHCb collaboration]

Measurement of the branching fraction ratio RK at large dilepton invariant mass / R. Aaij, A.S.W.A.. - In: JOURNAL OF HIGH ENERGY PHYSICS. - ISSN 1029-8479. - 2025:7(2025 Jul 17), pp. 198.1-198.36. [10.1007/jhep07(2025)198]

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

S. Cesare;C. Mancuso;D. Marangotto;N. Neri;G. Tonani;T. Tork;Z. Wang;
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. [The LHCb collaboration]
B Physics; Flavour Changing Neutral Currents; Flavour Physics; Hadron-Hadron Scattering;
Settore PHYS-01/A - Fisica sperimentale delle interazioni fondamentali e applicazioni
   European Particle physics Latin American NETwork
   EPLANET
   European Commission
   SEVENTH FRAMEWORK PROGRAMME - SP3-People - Marie-Curie Actions
   246806
17-lug-2025
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/1251376
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