Emergent 2HDM in the Low-Skiba-Smith little Higgs model: Musings from flavor and electroweak physics

The low-energy effective theory (similar to TeV) of the little Higgs model with SU(6)/Sp(6), as proposed by Low, Skiba, and Smith (LSS), exhibits a two-Higgs-doublet model (2HDM) structure. The symmetry dictates interesting Yukawa patterns, translating to nontrivial fermion couplings with both of the Higgs doublets. The couplings of the scalars with the fermions can induce flavor-changing neutral currents (FCNC), which get constraints from flavor physics observables such as BR(B -> X-s gamma), B-s - (B) over bar (s) mixing, etc. The precision measurement of the Zb (b) over bar vertex, the top and Higgs masses along with other Higgs coupling measurements at the Large Hadron Collider (LHC) also enforce severe restrictions on the LSS model. Direct LHC search results of beyond-the-Standard-Model (BSM) particles also impose bounds on the masses. We probe the LSS model in view of the above constraints through a random scan in the multidimensional parameter space. We observe, contrary to the general 2HDM scenario, that the emergent 2HDM from the LSS model is less constrained from the flavor data and the Zb (b) over bar measurement but is severely constrained from the electroweak (EW) searches at the LHC. From the flavor data and Zb (b) over bar, we find that the charged Higgs mass is relaxed, with tan beta being restricted to 0.5-5, whereas the charged Higgs mass is pushed to larger than 1 TeV along with tan beta being further restricted to < 3 when the LHC bounds are incorporated.