Confronting top A_(FB) with parity violation constraints

Abstract

We consider the implications of low-energy precision tests of parity violation on t-channel mediator models explaining the top A_(FB) excess measured by the CDF and D0 Collaborations. Flavor-violating u−t or d−t couplings of new scalar or vector mediators generate at one-loop an anomalous contribution to the nuclear weak charge. As a result, atomic parity violation constraints disfavor at ≳ 3σ t-channel models that give rise to a greater than 20% A_(FB) at the parton level for M_(tt̄) > 450 GeV while not producing too large a tt̄ cross section. Even stronger constraints are expected through future measurements of the proton weak charge by the Qweak experiment.

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