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

Abstract: An angular analysis of the B ⁰ → 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 (q ²) interval between 0.002 and 1.120 GeV ²/c ⁴. 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 q ² 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.]