Flavor Flux Correlators, Forward-Backward Asymmetries, and Anomalies

Abstract

Flavor plays a crucial role in the structure of the Standard Model. As such, many important collider physics measurements incorporate the flavor information of detected hadrons. Recent progress in the study of energy correlators has enabled collider physics measurements of energy flux to be reformulated as operator statements. In this Letter, we introduce flavor flux correlators, which measure the angular distribution and correlations of flavor quantum numbers. We emphasize a unique feature of heavy flavor flux correlators as compared to correlators of other charges, namely the $b$ and $c$ flavor quantum numbers are gapped at the heavy quark mass scale, making them a particularly clean perturbative observables, with $\mathcal{O}(Λ_{\text{QCD}}/m_Q)$ suppressed non-perturbative power corrections. As an application, we reformulate the heavy quark forward-backward asymmetry as a macroscopic consequence of a mixed electroweak anomaly of the heavy-quark flavor current. Using the relation to the anomaly, we compute the flavor flux correlator analytically at next-to-next-to-next-to-leading order and verify using parton shower simulations that non-perturbative corrections are suppressed, as expected from the gapped nature of the heavy flavor quantum numbers. Flavor flux correlators can be measured using archival electron-positron collision data, as well as at Belle II and future colliders.