Forward-backward tt¯ asymmetry from anomalous stop pair production

We analyze a simple Standard Model (SM) extension with only two new light fields: a scalar partner of the top t˜ (with mass above mt) and a light neutral fermion χ0 (with mass of a few GeV), coupled to SM quarks via Yukawa interaction. We show that such model can lead to a significant enhancement of the forward-backward asymmetry in tt¯ production at the Tevatron via the additional tt¯ pairs produced from t˜t˜† decays. The model satisfies existing constraints on new-physics searches both at low and high energies, and could even address the cosmological dark-matter abundance. The implications for future searches at the LHC are briefly outlined.