Exclusive Window onto Higgs Yukawa Couplings

We show that both flavor-conserving and flavor-violating Yukawa couplings of the Higgs boson to first- and second-generation quarks can be probed by measuring rare decays of the form $h\to MV$, where $M$ denotes a vector meson and $V$ indicates either $\gamma$, $W$ or $Z$. We calculate the branching ratios for these processes in both the standard model and its possible extensions. We discuss the experimental prospects for their observation. The possibility of accessing these Higgs couplings appears to be unique to the high-luminosity LHC and future hadron colliders, providing further motivation for those machines.

Figure 1

Direct-amplitude diagram (left) and indirect-amplitude diagram (right) contributing to $h\to \varphi \gamma$.

Figure 2

The expected deviation in the branching ratio $h\to \varphi \gamma$ relative to its SM value as a function of ${\kappa }_{\gamma }$ and ${\overline{\kappa }}_s$.