QCD Calculations of Heavy Quarkonium States

Recent results on the QCD analysis of bound states of heavy $\bar{q}q$ quarks are reviewed, paying attention to what can be derived from the theory with a reasonable degree of rigour. We report a calculation of $\bar{b}c$ bound states; a very precise evaluation of $b, c$ quark masses from quarkonium spectrum; the NNLO evaluation of $Υ\to e^+e^-$; and a discussion of power corrections. For the $b$ quark {\sl pole} mass we get, including $O(m_c^2/m_b^2)$ and $O(α_s^5\log α_s)$ corrections, $m_b=5.020\pm0.058 GeV$; and for the $\bar{MS}$ mass the result, correct to $O(α_s^3)$, $O(m_c^2/m_b^2)$, $\bar{m}_b(\bar{m}_b)=4.286\pm0.036 GeV$. For the decay $Υ\to e^+e^-$, higher corrections are too large to permit a reliable calculation, but we can predict a toponium width of $13\pm1 keV$.

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