Determining tanβ with neutral and charged Higgs bosons at a future e+e− linear collider

The ratio of neutral Higgs field vacuum expectation values, tanβ, is one of the most important parameters to determine in either the minimal supersymmetric standard model (MSSM) or a general type-II two-Higgs doublet model (2HDM). Assuming an energy and integrated luminosity of s=500 GeV and L=2000 fb−1 at a future linear collider (LC), we show that a very accurate determination of tanβ will be possible for low and high tanβ values by measuring the production rates of Higgs bosons and reconstructing Higgs boson decays. In particular, based on a TESLA simulation, and assuming no other light Higgs bosons and 100⩽mA⩽200 GeV, we find that the rate for the process e+e−→bb̄A→bb̄bb̄ provides a good determination of tanβ at high tanβ. In the MSSM Higgs sector, in the sample case of mA=200 GeV, we find that the rates for e+e−→bb̄A+bb̄H→bb̄bb̄ and for e+e−→HA→bb̄bb̄ provide a good determination of tanβ at high and low tanβ, respectively. We also show that the direct measurement of the average total widths of the H and A in e+e−→HA→bb̄bb̄ events provides an excellent determination of tanβ at large values. In addition, the charged Higgs boson process e+e−→H+H−→tb̄t̄b has been studied. The sensitivity to tanβ at the LHC obtained directly from heavy Higgs boson production is briefly compared to the LC results.