Determination of $\tan \beta$ at a Future $e^{+}{e}^{-}$ Linear Collider

It is widely stated that the ratio of neutral Higgs field vacuum expectation values, $\text{tanb}$, is one of the most difficult 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 $\text{rts}=500\text{gev}$ and $\text{call}=2000\text{fbi}$, we show that a very accurate determination of $\text{tanb}$ will often be possible using Higgs production rates and/or Higgs decays. Based on a TESLA simulation, and assuming no other light Higgs bosons and $100\le m_A\le 200\text{gev}$, we find that the rate for the process $\epem\to b\anti b A \to b\anti b b\anti b$providesanexcellentdeterminationof$\tanb$athigh$\tanb$\mathrm{.}IntheMSSMHiggssector,theratefor$\epem\to b\anti b A+ b\anti b H \to b\anti b b\anti b$($\epem\to HA \to b\anti b b\anti b$)providesagooddeterminationof$\tanb$athigh(low)$\tanb$, respectively, at moderate $m_A$ values. We also show that direct measurement of the average total width of the $H$ and $A$ in $\epem\to HA \to b\anti b b\anti b$eventsprovidesanexcellentdeterminationof$\tanb$atlarge$\tanb$.