Beyond Higgs couplings: probing the Higgs with angular observables at future e+e− colliders

A bstractWe study angular observables in the e+e−→ZH→ℓ+ℓ−bb¯$$ {e}^{+}{e}^{-}\to ZH\to {\ell}^{+}{\ell}^{-}b\overline{b} $$ 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$$ \sqrt{s}=240 $$ GeV and 5 (30) ab−1 integrated luminosity. We then determine the projected sensitivity to a range of operators relevant for he Higgs-strahlung 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 both probing BSM corrections to the HZγ coupling and constraining the “blind spot” in indirect limits on supersymmetric scalar top partners.

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