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A tale of $Z$+jet: SMEFT effects and the Lam-Tung relation

Rhorry Gauld, Ulrich Haisch, Joachim Weiss

SciPost Phys. 18, 148 (2025) · published 6 May 2025

Abstract

We derive constraints on dimension-six light-quark dipole operators within the Standard Model (SM) effective field theory, based on measurements of $Z$ production at SLC and LEP, as well as $Z$+jet production at the LHC. Our new constraints exclude the parameter space that could potentially explain the observed discrepancy between theoretical predictions and experimental data for the Lam-Tung relation. With these updated limits, we model-independently determine the maximum possible influence that beyond-SM contributions could have on the angular coefficients $A_0$ and $A_2$, which enter the Lam-Tung relation.


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