Quark flavour-violating Higgs decays at the ILC

Abstract

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 $e^{+}{e}^{-}\to bj+E_T^{\text{miss}}$. At 500 GeV, the expected $95$% CL upper limit on $\mathcal{B}(h\to bj)$ is of order $10^{-3}$. Correspondingly, a $5\sigma$ discovery is expected to be possible for branching ratios as low as a few $10^{-3}$.

Comments: 9 pages, 6 figures, 5 tables. Minor typos fixed with respect to v2