Probing the Higgs with angular observables at future e⁺e^- colliders

I summarize our recent works on using differential observables to explore the physics potential of future e⁺e^- colliders in the framework of Higgs effective field theory. This proceeding is based upon Refs. 1 and 2. We study angular observables in the e⁺e^- → ZHl⁺l^-bb channel at future circular e⁺e^- colliders such as CEPC and FCC-ee. Taking into account the impact of realistic cut acceptance and detector effects, we forecast the precision of six angular asymmetries at CEPC (FCC-ee) with center-of-mass energy s = 240 GeV and 5 (30) ab-1 integrated luminosity. We then determine the projected sensitivity to a range of operators relevant for the Higgsstrahlung process in the dimension-6 Higgs EFT. Our results show that angular observables provide complementary sensitivity to rate measurements when constraining various tensor structures arising from new physics. We further find that angular asymmetries provide a novel means of constraining the "blind spot" in indirect limits on supersymmetric scalar top partners. We also discuss the possibility of using ZZ-fusion at e⁺e^- machines at different energies to probe new operators.