Place your bets on Higgs mass

The grey bands show the remaining allowed regions for the Higgs boson mass, after exclusions obtained at LEP, the Tevatron and the LHC.

The curve represents the mass fit for the W boson.

In quantum mechanics, the W boson is the carrier of the weak nuclear force. The weak force is responsible for beta-decay in radioactivity and for nuclear reactions in the burning of the sun. But the W boson has another important responsibility. From the precise measurement of the W boson’s mass and the measurements of other particles in the Standard Model, we can deduce the mass of the Higgs boson. Currently, the uncertainty on W boson’s mass is the limiting factor in our ability to predict the mass of the Higgs.

Measuring the W boson’s mass requires a detailed modeling of detector response to a level unprecedented at CDF. CDF scientists performed independent measurements of the Z boson mass by examining both the electron and muon decay channels, validating the detector model. These are the most precise Z boson mass measurements performed at a hadron collider, and they are in excellent agreement with the high-precision measurements made at the LEP experiments at CERN.

Using 2.2 inverse femtobarns of data, CDF has measured the mass of the W boson to be 80387 ± 12 (stat) &plusmn: 15 (syst) = 80387 ± 19 MeV/c2. This is the most precise measurement of W boson’s mass to date, exceeding the precision of all previous measurements combined. Theoretical calculations including this new W mass measurement with the previous world average predict the mass of the Higgs boson to be less than 145 GeV/c2 with high confidence. This range is also favored by direct Higgs searches at the Tevatron and the LHC.

If the Higgs boson shows up in this mass range, it will be a spectacular confirmation of the Standard Model. If it does not, it will be an even more spectacular demonstration of new physics awaiting discovery. It’s time to place your bets.

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—Edited by Andy Beretvas

These physicists were responsible for this analysis. Top row from left: Daniel Beecher, University College, London; Ilija Bizjak, University College, London; Chris Hays, Oxford University. Second row: Bodhitha Jayatilaka, Duke; Ashutosh Kotwal, Duke University; Sarah Malik, University College, London. Third row: Tom Riddick, University College, London; Ravi Shekhar, Duke University; Oliver Stelzer-Chilton, TRIUMF. Fourth row: Siyuan Sun, Duke University; Dave Waters, University College, London; Yu Zeng, Duke University.