Shedding light on the $t \bar t$ asymmetry: the photon handle
  We investigate a charge asymmetry in $t \bar t \gamma$ production at the LHC that provides complementary information to the measured asymmetries in $t \bar t$ production. We estimate the experimental uncertainty in its measurement at the LHC with 8 and 14 TeV. For new physics models that simultaneously reproduce the asymmetry excess in $t \bar t$ at the Tevatron and the SM-like asymmetry at the LHC, the measurement in $t \bar t \gamma$ at the LHC could exhibit significant deviations with respect to the SM prediction. 
J. A. Aguilar-Saavedra, E. Alvarez, A. Juste, F. Rubbo
hep-ph hep-ex