Determination of tanâ¡β from the Higgs boson decay at linear colliders

In the two Higgs doublet models, tanâ¡β is an important parameter, which is defined as the ratio of the vacuum expectation values of the doublets. We study how accurately tanâ¡β can be determined at linear colliders via the precision measurement of the decay branching fraction of the standard model (SM)-like Higgs boson. Since the effective coupling constants of the Higgs boson with the weak gauge bosons are expected to be measured accurately, the branching ratios can be precisely determined. Consequently, tanâ¡β can be determined with a certain amount of accuracy. Comparing the method to those using direct production of the additional Higgs bosons, we find that, depending on the type of Yukawa interactions, the precision measurement of the decay of the SM-like Higgs boson can be the best way to determine tanâ¡β, when the deviations in the coupling constants with the gauge boson from the SM prediction are observed at linear colliders.