Improved Estimate of the Scalar-Glueball Mass

We present results for the $0^{++}$ glueball mass ($m_G$) and the string tension ($\sigma$) in pure gauge lattice QCD with a four-parameter improved action. We suggest and confirm that previous estimates for $\frac{m_G}{\sqrt{\sigma }}$ have been too low because of the influence of the unphysical and nonuniversal phase structure in the fundamental-adjoint coupling plane. We find that $m_G\approx 1200-1400$ MeV using $\sqrt{\sigma }=420\mathrm{}$ MeV.