Such a model can be described in terms of six physical parameters: four Higgs masses ( m h , m H , m A , m H ± ± ), the ratio of the two vacuum expectation values ( tan ⁡ ⁡ β β ) and the mixing angle ( α α ) which diagonalizes the mass matrix of the neutral CP even Higgses. The SM uses only 2 parameters: the mass of the Higgs and its vacuum expectation value.