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Test of lepton universality with ∧0bpK-+- decays

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Original languageEnglish
Article number40
JournalJournal of High Energy Physics
Publication statusPublished - 11 May 2020


The ratio of branching fractions of the decays $ {\Lambda}_b^0 $ → pK$^{−}$e$^{+}$e$^{−}$ and $ {\Lambda}_b^0 $ → pK$^{−}$μ$^{+}$μ$^{−}$,$ {R}_{pK}^{-1} $, is measured for the first time using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb$^{−1}$ recorded with the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV. In the dilepton mass-squared range 0.1 < q$^{2}$< 6.0 GeV$^{2}$/c$^{4}$ and the pK$^{−}$ mass range m(pK$^{−}$) < 2600 MeV/c$^{2}$, the ratio of branching fractions is measured to be $ {R}_{pK}^{-1}={1.17}_{-0.16}^{+0.18}\pm 0.07 $, where the first uncertainty is statistical and the second systematic. This is the first test of lepton universality with b baryons and the first observation of the decay $ {\Lambda}_b^0 $ → pK$^{−}$e$^{+}$e$^{−}$.[graphic not available: see fulltext]

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