Angular analysis of the B⁰ → K^*0e⁺e⁻ decay in the low-q² region

Abstract: An angular analysis of the B⁰ → K^*0e⁺e⁻ decay is performed using a data sample, corresponding to an integrated luminosity of 3.0 fb⁻¹, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV during 2011 and 2012. For the first time several observables are measured in the dielectron mass squared (q²) interval between 0.002 and 1.120 GeV²/c⁴. The angular observables F_L and A_T ^Re which are related to the K^*0 polarisation and to the lepton forward-backward asymmetry, are measured to be F_L = 0.16 ± 0.06 ± 0.03 and A_T ^Re = 0.10 ± 0.18 ± 0.05, where the first uncertainty is statistical and the second systematic. The angular observables A_T ⁽²⁾ and A_T ^Im which are sensitive to the photon polarisation in this q² range, are found to be A_T ⁽²⁾ = − 0.23 ± 0.23 ± 0.05 and A_T ^Im = 0.14 ± 0.22 ± 0.05. The results are consistent with Standard Model predictions.[Figure not available: see fulltext.]