Forward Tevatron Tops and Backward LHC Tops with Associates
  The anomalous forward-backward asymmetry (A_FB) in t tbar production at the Tevatron is in apparent contradiction with the t tbar charge asymmetry (A_C) measurements at the LHC, which agree well with the standard model predictions. We argue that associated production of a state with [u tbar] flavor quantum numbers can lead to a sizable negative contribution to A_C. Exchange of such a resonance in the t-channel would lead to positive contributions to A_FB and A_C, as has been extensively discussed in the literature. Given the additional negative A_C contribution, both the Tevatron and LHC data can be naturally accommodated within this framework. A simple realization of this setup is the well known example of a Z' with flavor off-diagonal up-top couplings. We provide a detailed study of this model, demonstrating that it indeed reproduces the t tbar asymmetry data, and is compatible with other constraints, e.g. t+jet resonance searches, t tbar inclusive jet multiplicities, and atomic parity violation. 
Jure Drobnak, Alexander L. Kagan, Jernej F. Kamenik, Gilad Perez, and   Jure Zupan
hep-ph hep-ex