This paper presents single lepton and dilepton
kinematic distributions measured in dileptonic tt
¯ events produced
in 20.2 fb−1 of √s = 8 TeV pp collisions recorded
by the ATLAS experiment at the LHC. Both absolute and
normalised differential cross-sections are measured, using
events with an opposite-charge eμ pair and one or two btagged
jets. The cross-sections are measured in a fiducial
region corresponding to the detector acceptance for leptons,
and are compared to the predictions from a variety of
Monte Carlo event generators, as well as fixed-order QCD
calculations, exploring the sensitivity of the cross-sections
to the gluon parton distribution function. Some of the distributions
are also sensitive to the top quark pole mass;
a combined fit of NLO fixed-order predictions to all the
measured distributions yields a top quark mass value of
mpole
t = 173.2±0.9±0.8±1.2 GeV, where the three uncertainties
arise from data statistics, experimental systematics,
and theoretical sources.