Test of lepton universality with B[superscript 0] → K[superscript *0] ℓ[superscript +] ℓ[superscript −] decays

Abstract

A test of lepton universality, performed by measuring the ratio of the branching fractions of the B[superscript 0] → K[superscript *0] μ[superscript +] μ[superscript −] and B[superscript 0] → K[superscript *0] e[superscript +] e[superscript −] decays, R[subscript K[superscript *0]], is presented. The K [superscript *0] meson is reconstructed in the final state K[superscript +] π[superscript −], which is required to have an invariant mass within 100 MeV/c[superscript 2] of the known K[superscript *](892)[superscript 0] mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of about 3 fb[superscript −1], collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ratio is measured in two regions of the dilepton invariant mass squared, q[superscript 2], to be (Formula presented.) The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94] . The results, which represent the most precise measurements of RK*0 to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q[superscript 2] regions, respectively.[Figure not available: see fulltext.].The corresponding 95.4% confidence level intervals are [0.52, 0.89] and [0.53, 0.94]. The results, which represent the most precise measurements of R[subscript K[superscript ∗0]] to date, are compatible with the Standard Model expectations at the level of 2.1–2.3 and 2.4–2.5 standard deviations in the two q[superscript 2] regions, respectively.