The first test of lepton flavor universality between muons and electrons using 𝐵+→𝐾+𝜋+𝜋−ℓ+ℓ− (ℓ =𝑒, 𝜇) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment 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 𝐵+→𝐾+𝜋+𝜋−𝑒+𝑒− and 𝐵+→𝐾+𝜋+𝜋−𝜇+𝜇− decays is measured in the dilepton invariant-mass-squared range 1.1<𝑞2<7.0 GeV2/𝑐4 and is found to be 𝑅−1𝐾𝜋𝜋=1.31+0.18−0.17(stat) +0.12−0.09(syst), in agreement with the standard model prediction. The first observation of the 𝐵+ →𝐾+𝜋+𝜋−𝑒+𝑒− decay is also reported.
Test of Lepton Flavor Universality with B+ -> K+ pi + pi -\ell+ \ell- Decays
Bassi G.Membro del Collaboration Group
;Kleijne N.Membro del Collaboration Group
;Morello M. J.Membro del Collaboration Group
;Passaro D.Membro del Collaboration Group
;Pica L.Membro del Collaboration Group
;Riccardi D.Membro del Collaboration Group
;
2025
Abstract
The first test of lepton flavor universality between muons and electrons using 𝐵+→𝐾+𝜋+𝜋−ℓ+ℓ− (ℓ =𝑒, 𝜇) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment 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 𝐵+→𝐾+𝜋+𝜋−𝑒+𝑒− and 𝐵+→𝐾+𝜋+𝜋−𝜇+𝜇− decays is measured in the dilepton invariant-mass-squared range 1.1<𝑞2<7.0 GeV2/𝑐4 and is found to be 𝑅−1𝐾𝜋𝜋=1.31+0.18−0.17(stat) +0.12−0.09(syst), in agreement with the standard model prediction. The first observation of the 𝐵+ →𝐾+𝜋+𝜋−𝑒+𝑒− decay is also reported.| File | Dimensione | Formato | |
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PhysRevLett.134.181803.pdf
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