Constraining dimension-6 SMEFT with higher-order predictions for $p p \to t W$

Abstract

We study single-top production in association with a $W$ boson at the LHC as a probe of dimension-6 Standard Model Effective Field Theory (SMEFT) at leading order, next-to-leading order, and approximate next-to-next-to-leading order accuracy in QCD. The process is sensitive to operators that modify the top-quark weak and chromomagnetic dipole interactions, and we perform three-parameter linear and quadratic SMEFT fits using doubly differential top-quark distributions in transverse momentum and rapidity for the Run II and Run III configurations at the LHC. We provide a detailed account of the uncertainties and quantify the impact of the different uncertainty components across bins and perturbative orders. We find that effective scales up to 2 TeV can be probed in nonmarginalized fits, while in marginalized fits the corresponding scales are around 0.5 and 1.5 TeV for linear and quadratic fits, respectively.

Figures (28)

• Figure 1: The Feynman diagrams for the partonic process contributing to $p p \to t W^-$ at leading order.
• Figure 2: The relevant SMEFT Feynman rules for the partonic process of interest, adopted from Degrande:2020evl.
• Figure 3: The top-quark distributions in $tW^-$ production in the SM across the assumed bins at LO (left), NLO (center), and aNNLO (right) at 13 TeV.
• Figure 4: Comparison of LO, NLO, and aNNLO SM distributions (left) at 13 TeV, together with the corresponding $k$ factors (right) across the assumed bins.
• Figure 5: Linear SMEFT corrections to the top distributions characterized by $C_{tG}$, $C_{tW}$, and $C_p$ relative to the SM in percent at LO (left), NLO (center), and aNNLO (right) at 13 TeV.