Tevatron top A_(FB) versus LHC top physics

Abstract

We carry out a comprehensive analysis of models for top A_(FB) at CDF in light of new top data arriving from the LHC. We begin with a careful Tevatron analysis, considering in general which sets of effective vertices give rise to a large forward-backward asymmetry while suppressing the contribution to the total tt̄ cross-section. We show on general grounds that scalar models struggle to produce sufficient asymmetries consistent with CDF observations, while vector models can produce a large asymmetry with a less significant tension in the total cross-section and tt̄ invariant mass distribution at the Tevatron. We examine the essential observables of these models for top physics at LHC7 with 1 fb^(−1) of data, including the total cross-section, invariant mass distribution and number of additional jets in tt̄ events. In the case of t-channel mediators, the LHC total cross-section places a strong constraint on light mediators, while the Tevatron invariant mass distributions place strong constraints on heavy mediators that are able to produce the asymmetry. In particular, single mediator production at the LHC can contribute significantly to tt̄ + jets events and lead to a significant increase in the tt̄ cross-section, as well as in the ratio of top pair events with extra jets to events with no extra jets. Heavy axigluons are becoming increasingly squeezed by LHC7 tt̄ and dijet resonance searches. We conclude that LHC7 top analyses are rapidly closing the window for viable models of the CDF top A_(FB).

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