Shedding light on the tt¯ asymmetry: the photon handle

Abstract

We investigate a charge asymmetry in tt¯γtt¯γ production at the LHC that provides complementary information to the measured asymmetries in tt¯tt¯ production. We estimate the experimental uncertainty in its measurement at the LHC with 8 TeV and 14 TeV. We argue that, for new physics models that simultaneously reproduce the asymmetry excess in tt¯tt¯ production at the Tevatron and the SM-like asymmetry at the LHC, the measurement in tt¯γtt¯γ production at the LHC is likely to deviate from the SM prediction. In two new physics models studied in detail we find that the deviations could be significant and observable at the 14 TeV run.