Light charged Higgs bosons decaying to charm and bottom quarks in models with two or more Higgs doublets

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Searches for light charged Higgs bosons (H±) in the decay of top quarks, t -> H± b, are being carried out at the LHC and at the Tevatron. It is assumed that the dominant decay channels for such an H± state are either H± -> τνor H± -> cs, and separate searches are performed with comparable sensitivity to the parameters mₕ± and tanbeta of the scalar potential. The branching ratio for the decay H± -> cb can be as large as 80% in the Aligned Two Higgs Doublet Model and in models with three or more Higgs doublets with natural flavour conservation, while satisfying the constraint from b -> s gamma for mₕ± < mₜ. Although the current search strategy for H± -> cs is also sensitive to H± -> cb, a considerable gain in sensitivity could be obtained by tagging the b quark from the decay H± -> cb. Such an analysis, which could be readily performed at the Tevatron and in the 7 TeV and 8 TeV runs of the LHC, would probe a parameter space of the fermionic couplings of H± in the above models which at present cannot be probed by experimental observables in flavour physics.