Constraining Light-Quark Yukawa Couplings from Higgs Distributions

We propose a novel strategy to constrain the bottom and charm Yukawa couplings by exploiting Large Hadron Collider (LHC) measurements of transverse momentum distributions in Higgs production. Our method does not rely on the reconstruction of exclusive final states or heavy-flavor tagging. Compared to other proposals, it leads to an enhanced sensitivity to the Yukawa couplings due to distortions of the differential Higgs spectra from emissions which either probe quark loops or are associated with quark-initiated production. We derive constraints using data from LHC run I, and we explore the prospects of our method at future LHC runs. Finally, we comment on the possibility of bounding the strange Yukawa coupling.

Figure 1

The normalized $p_{T,h}$ spectrum of inclusive Higgs production at $\sqrt{s}=8\mathrm{TeV}$ divided by the SM prediction for different values of ${\kappa }_c$. Only ${\kappa }_c$ is modified, while the remaining Yukawa couplings are kept at their SM values.

Figure 2

The $\mathrm{\Delta }{\chi }^2=2.3$ and $\mathrm{\Delta }{\chi }^2=5.99$ regions in the ${\kappa }_c-{\kappa }_b$ plane following from the combination of the ATLAS measurements of the normalized $p_{T,h}$ distribution in the $h\to \gamma \gamma$ and $h\to Z{Z}^{*}\to 4\ell$ channels. The SM point is indicated by the black cross.

Figure 3

Projected future constraints in the ${\kappa }_c\text{−}{\kappa }_b$ plane. The SM point is indicated by the black cross. The figure shows our projections for the LHC run II (HL-LHC) with $0.3{\mathrm{ab}}^{-1}$ ($3{\mathrm{ab}}^{-1}$) of integrated luminosity at $\sqrt{s}=13\mathrm{TeV}$. The remaining assumptions entering our future predictions are detailed in the main text.