| The precise measurement of the mass of the W boson constitutes an important consistency check of the Standard Model (SM). Especially after the discovery of the 125 GeV Higgs boson at LHC, the SM is now for the first time a complete theoretical framework that provides interconnections among electroweak (EW) parameters such as the W boson mass, top quark mass, SM Higgs boson mass, etc.. Knowing the precisely measured W boson mass and all the other parameters, the SM can predict the SM-like Higgs boson mass. And similarly, the discovery of the Higgs boson with its mass measurement can inversely predict a "predicted" W boson mass. A comparison of the predicted W or Higgs mass with the directly measured values can provide an ultra-precise test of the SM, and has strong discrimination power of various theories beyond SM.
The Tevatron experiements D0 and CDF at Fermilab are currently the leading power in the W boson mass measurement. Last round of results from D0 and CDF published in 2012 improved the world average precision of the W boson mass from 23 MeV to 15 MeV. This is a huge effort took 5 years at CDF and 3 years at D0 of more than 20 people's hard work. It has been said to be the most difficult measurement at hadron colliders. There are still more than half of the D0 and CDF data waiting to be analyzed. In the meanwhile, the LHC efforts are coming, and the ILC and possibly circular Higgs Factory contributions will come in a foreseeable future.
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