The $e^{+}{e}^{-}\to ZH$ Process in the SMEFT Beyond Leading Order

Abstract

We systematically study potential effects of Beyond the Standard Model physics in the $e^{+}{e}^{-}\to ZH$ process. To this end, we include all relevant dimension-6 Standard Model Effective Field Theory operators and work to next-to-leading order (NLO) accuracy in the electroweak coupling. We consider both polarized and unpolarized electron and positron beams and present results for $\sqrt{s}=240,365$ and $500\mathrm{GeV}$, emphasizing contributions where the NLO predictions differ significantly from the leading order results. At NLO, a sensitivity arises to operators that do not contribute at tree level, such as the Higgs tri-linear coupling, CP-violating operators, and dimension-6 operators involving the top quark, among many others. We compare the prospects of future $e^{+}{e}^{-}$ colliders to explore these new physics effects with existing measurements from the LHC, electron EDMs (for CP violating operators), and Z pole measurements.

45 pages, 22 figures, 8 tables (v2: version accepted for publication in JHEP, v3: numbers in paper harmonized with git repository which will always have the most up-to-date results)