Quark flavour-violating Higgs decays at the ILC

Flavour-violating Higgs interactions are suppressed in the Standard Model such that their observation would be a clear sign of new physics. We investigate the prospects for detecting quark flavour-violating Higgs decays in the clean ILC environment. Concentrating on the decay to a bottom and a light quark j, we identify the dominant Standard Model background channels as coming from hadronic Standard Model Higgs decays with mis-identified jets. Therefore, good flavour tagging capabilities are essential to keep the background rate under control. Through a simple cut-based analysis, we find that the most promising search channel is the two-jet plus missing energy signature e⁺e⁻→bj+Ɇ_T. At 500 GeV, the expected 95 % CL upper limit on B(h→bj) is of order 10⁻³. Correspondingly, a 5 σ discovery is expected to be possible for branching ratios as low as a few 10⁻³.