# Does two Higgs doublet model predicts two Higgs bosons?

Does 2HDM predict two higgs boson? Why two doublets are needed? I need a simplified answer as i am new to BSM

• It predicts 5 higgs bosons including the usual one. Usually called h (light scalar), H (heavy scalar), A (pseudo-scalar), H+ (charged positive Higgs boson) and H- (charged negative Higgs boson). I'd answer but don't have time to look up a citation. Not entirely obvious in 2HD models if the SM Higgs is h or H. – ohwilleke Feb 9 at 20:49

You may guess it by counting the number of degrees of freedom. One doublet corresponds to 4 real degrees of freedom. However the Higgs breaks $$U(1)\times SU(2)$$ gauge symmetry to $$U(1)$$. This requires the appearance of three Goldstone modes - one neutral and two charged ones conjugated to each other. Those 3 Goldstones are not physical and instead neutral $$Z$$ and charged $$W^\pm$$ bosons get longitudinal polarizations. This leaves us with only one neutral Higgs boson in the physical sector.