Hunting New Physics with Lepton Flavor Universality Violations in B Decays and Asymmetries in Top Pair Production

Present measurements of b→cτν and b→uτν transitions differ from the standard model predictions of lepton flavor universality by almost 4σ. We examine new physics (NP) interpretations of this anomaly. An effective field theory analysis shows that minimal flavor violating models are not preferred as an explanation, but are also not yet excluded. Allowing for general flavor violation, right-right vector and right-left scalar quark currents are identified as viable candidates. We discuss explicit examples of two Higgs doublet models, leptoquarks as well as quark and lepton compositeness. In the second part, we show that the charge asymmetry in tt¯ production at the LHC, AC, and the forward-backward asymmetry at the Tevatron, AFB, are in general not tightly correlated. They can even have opposite signs, if the underlying NP model is general enough. We demonstrate this using an example NP model featuring a light axigluon. The small value of AC measured at the LHC is thus shown not to exclude a NP interpretation of the anomalously large AFB at the Tevatron. We identify two observables where significant NP effects are still expected at the Tevatron and the LHC, the b¯b production forward-backward asymmetry and spin polarizations of the pair-produced tops and anti-tops