Implications of the CDF t\bar{t} Forward-Backward Asymmetry for Boosted Top Physics

TL;DR

This paper investigates how new physics at high energy scales could influence top quark observables, particularly the forward-backward asymmetry, and discusses the limitations of current models in explaining boosted top jet enhancements.

Contribution

It analyzes the impact of effective four-quark operators on top quark asymmetries and cross sections, highlighting potential explanations and limitations of recent experimental anomalies.

Findings

Effective operators can modify top asymmetry and cross sections.

Boosted jet cross section enhancement is limited to 60%.

Recent anomalies may be due to QCD effects or higher-order new physics.

Abstract

New physics at a high scale Lambda can affect top-related observables at O(1/Lambda^2) via the interference of effective four quark operators with the SM amplitude. The (\bar{u} gamma_mu gamma^5 T^a u)(\bar{t} gamma^mu gamma^5 T^a t) operator modifies the large M_{t\bar{t}} forward-backward asymmetry, and can account for the recent CDF measurement. The (\bar{u} gamma_mu T^a u)(\bar{t} gamma^mu T^a t) operator modifies the differential cross section, but cannot enhance the cross section of ultra-massive boosted jets by more than 60%. The hint for a larger enhancement from a recent CDF measurement may not persist future experimental improvements, or may be a QCD effect that is not accounted for by leading order and matched Monte Carlo tools or naive factorization. If it comes from new physics, it may stem from new light states or an O(1/Lambda^4) new physics effect.