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

We study angular observables in the $$ {e}^{+}{e}^{-}to zhto {ell}^{+}{ell}^{-}boverline{b} $$ 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 $$ sqrt{s}=240 $$ 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.