Combination of CDF and DO results on the mass of the top quark using up to 9.7 fb−1^{-1} at the Tevatron

18 pages, 4 figuresWe summarize the current top-quark mass measurements from the CDF and DO experiments at Fermilab. We combine published Run I (1992--1996) results with the most precise published and preliminary Run II (2001--2011) measurements based on data corresponding to up to 9.7 fb$^{-1}$ of $p\bar{p}$ collisions. Taking correlations of uncertainties into account, and combining the statistical and systematic uncertainties, the resulting preliminary Tevatron average mass of the top quark is $M_{top} = 174.34 \pm 0.64 ~GeV/c^2$, corresponding to a relative precision of 0.37%