Higgs boson to charm quark decay in vector boson fusion plus a photon

Experimentally probing the charm-Yukawa coupling in the LHC experiments is important, but very challenging due to an enormous QCD background. We study a new channel that can be used to search for the Higgs decay $H\to c\overline{c}$, using the vector boson fusion (VBF) mechanism with an associated photon. In addition to suppressing the QCD background, the photon gives an effective trigger handle. We discuss the trigger implications of this final state that can be utilized in ATLAS and CMS. We propose a novel search strategy for $H\to c\overline{c}$ in association with VBF jets and a photon, where we find a projected sensitivity of about 13 times the SM charm-Yukawa coupling at 95% ${\mathrm{CL}}_s$ at High Luminosity LHC (HL-LHC). Our result is comparable and complementary to existing projections at the HL-LHC. We also discuss the implications of increasing the center of mass collision energy to 30 TeV and 100 TeV.

Figure 1

Representative Feynman diagrams of the signal channel (left) and QCD multi-jet background (right).

Figure 2

Distributions of useful observables for signal (blue) and multi-jet background (red) after pre-selections.

Figure 3

Distributions of useful observables for signal (blue) and multi-jet background (red) after pre-selections.

Figure 4

Distribution of the invariant mass of the signal $c$-jet pair after cuts.

Figure 5

The distribution of the BDT score with low, medium and high signal region defined as $-0.07$-0.01, 0.01-0.08 and $>0.08$ respectively (top) and receiver operating characteristic (ROC) curve of the BDT (bottom).

Figure 6

Distribution of the invariant mass of the signal c-jet pair for events in different BDT score intervals, corresponding to the categories: low, medium and high signal.