Probing New Physics in Higgs Couplings to Fermions using an Angular Analysis

The standard-model Higgs boson couples to quarks through a parity-even scalar $Hq{\bar q}$ coupling. We show that the rare Higgs decay $H\to VZ$, where $V$ is a vector quarkonium state such as $J/\psi$ ($c{\bar c}$) or $\Upsilon(1S)$ ($b{\bar b}$), can be used to search for the presence of a parity-odd pseudoscalar $Hq{\bar q}$ coupling. Since both $V$ and $Z$ can decay to a pair of charged leptons, this presents an experimentally-clean channel that can be observed at the high-luminosity LHC or a future hadron collider. The P-even and P-odd $Hq{\bar q}$ couplings can be measured by analyzing the angular distribution of the final-state leptons.