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

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...

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Main Authors: Aaij, Roel (Author) , Bachmann, Sebastian (Author) , Carus, Leon (Author) , Caspary, Rowina (Author) , Celani, Sara (Author) , Cocha Toapaxi, Carlos (Author) , De Cian, Michel (Author) , Dittmann, Lucas (Author) , Esen, Sevda (Author) , Glaser, Fabian (Author) , Günther, Paul André (Author) , Han, Xiaoxue (Author) , Hansmann-Menzemer, Stephanie (Author) , Herrero Gascón, Paula (Author) , Langenbruch, Christoph (Author) , Leverington, Blake (Author) , Marks, Jörg (Author) , Morgenthaler, Maurice Pierre (Author) , Roy, Shreya (Author) , Ruiz Diaz, Miguel (Author) , Tat, Martin Duy (Author) , Tuci, Giulia (Author) , Uecker, Lennart Henning (Author) , Unverzagt, Daniel Joachim (Author) , Uwer, Ulrich (Author) , Wang, Chishuai (Author) , Zhao, Ya (Author) , Zhelezov, Alexey (Author)
Corporate Author: LHCb Collaboration (Author)
Format: Article (Journal)
Language:English
Published: 17 July 2025
In: Journal of high energy physics
Year: 2025, Issue: 7, Pages: 1-36
ISSN:1029-8479
DOI:10.1007/JHEP07(2025)198
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.1007/JHEP07(2025)198
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Author Notes:the LHCb collaboration*
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Summary: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 $$ {R}_K=1.0{8}_{-0.09}^{+0.11}{\left(\textrm{stat}\right)}_{-0.04}^{+0.04}\left(\textrm{syst}\right) $$, 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.
Item Description:Veröffentlicht: 17. Juli 2025
*The LHCb collaboration: R. Aaij, S. Bachmann, L. Carus, R. Caspary, S. Celani, C. Cocha Toapaxi, M. De Cian, L. Dittmann, S. Esen, F.C. Glaser, P.A. Günther, X. Han, S. Hansmann-Menzemer, P. Herrero Gascon, C. Langenbruch, B. Leverington, J. Marks, M.P. Morgenthaler, S.R. Roy, M. Ruiz Diaz, M.D. Tat, G. Tuci, L.H. Uecker, D.J. Unverzagt, U. Uwer, C. Wang, Y. Zhao, A. Zhelezov [und sehr viele weitere Personen]
Im Titel ist die Buchstabe "K" tiefgestellt
Gesehen am 02.02.2026
Physical Description:Online Resource
ISSN:1029-8479
DOI:10.1007/JHEP07(2025)198

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