Andy Chisholm

The Standard Model (SM) Higgs boson is expected to decay to a charm quark pair in around 3% of cases. While this number seems small, the success of the LHC Higgs boson measurement programme is such that this contribution represents one of the largest expected contributions to the total Higgs boson decay width for which we have no experimental evidence. Furthermore, all experimental evidence for Yukawa couplings is limited to the third generation fermions and the smallness of the SM charm quark Yukawa coupling makes it particularly sensitive to modifications from potential physics beyond the SM. I will describe a novel charm jet tagging algorithm recently commissioned by the ATLAS experiment and discuss how it can be employed to perform the first direct search for Higgs boson decays to charm quark pairs with the ATLAS experiment (Phys. Rev. Lett. 120 (2018) 211802, arXiv:1802.04329). Looking beyond this LHC Run 2 result, the prospects and projected sensitivity for this channel at the HL-LHC will also be discussed.