Anomalous Higgs couplings in angular asymmetries of H --> Zl+l- and e+e- --> HZ

TL;DR

This paper investigates how anomalous Higgs couplings affect angular asymmetries in specific Higgs decay and production processes, revealing potential signs of physics beyond the Standard Model through detailed analytical expressions.

Contribution

It provides approximate formulas for angular asymmetries sensitive to dimension-six operators, highlighting their ability to uncover hidden BSM effects in Higgs interactions.

Findings

Asymmetries can reach several percent due to BSM couplings.

Certain asymmetries are unaffected by other observables, aiding in BSM detection.

Differences in asymmetries between processes offer complementary search strategies.

Abstract

We study in detail the impact of anomalous Higgs couplings in angular asymmetries of the crossing-symmetric processes H --> Zl+l- and e+e- --> HZ. Beyond Standard Model physics is parametrized in terms of the SU(3)xSU(2)_LxU(1)_Y dimension-six effective Lagrangian. In the light of present bounds on d = 6 interactions we study how angular asymmetries can reveal non-standard CP-even and CP-odd couplings. We provide approximate expressions to all observables of interest making transparent their dominant dependence on anomalous couplings. We show that some asymmetries may reveal BSM effects that are hidden in other observables. In particular, CP-even and CP-odd d = 6 HZgamma couplings as well as (to a lesser extent) HZll contact interactions can generate asymmetries at the several percent level, while having small or no effects on the di-lepton invariant mass spectrum of H --> Zl+l-. Finally, the higher di-lepton invariant mass probed in e+e- --> HZ leads to interesting differences in the asymmetries with respect to those of H --> Zl+l- that may lead to complementary anomalous coupling searches at the LHC and e+e- colliders.