Strong constraints on the b ā sĪ³ photon polarisation from B 0 ā K *0 e + e ā decays
Published version
Peer-reviewed
Repository URI
Repository DOI
Change log
Authors
Abstract
Abstract: An angular analysis of the B0 ā K0e+eā decay is performed using a data sample corresponding to an integrated luminosity of 9 fbā1 of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared (q2) interval between 0.0008 and 0.257 GeV2, where the rate is dominated by the B0 ā K0Ī³ transition with a virtual photon. The fraction of longitudinal polarisation of the K*0 meson, FL, is measured to be FL = (4.4 Ā± 2.6 Ā± 1.4)%, where the first uncertainty is statistical and the second systematic. The ATRe observable, which is related to the lepton forward-backward asymmetry, is measured to be ATRe = ā0.06 Ā± 0.08 Ā± 0.02. The AT2 and ATIm transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be AT2 = 0.11 Ā± 0.10 Ā± 0.02 and ATIm = 0.02 Ā± 0.10 Ā± 0.01. The results are consistent with Standard Model predictions and provide the worldās best constraint on the b ā sĪ³ photon polarisation.