First Measurement of the W Boson Mass with CDF in Run II

Chris Hays(b,c), Ashutosh Kotwal(b), Larry Nodulman(a), Oliver Stelzer-Chilton(c,d), William Trischuk(d), Ian Vollrath(d)
(a)Argonne National Laboratory, (b)Duke University, (c)University of Oxford, (d)University of Toronto

MW = 80413 48 MeV/c2
(the world's most precise single measurement)
Transverse Mass Fits

  • Abstract
  • Measurement Technique
  • Momentum Scale Calibration
  • Energy Scale Calibration
  • Recoil Calibration
  • Production and Decay Model
  • Additional W Mass Fits
  • Uncertainty Tables
  • New MW vs Mtop Plots

  • Winter 2007 Conference Note
  • Fermilab W&C Talk January 5th, 2007


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    We present a first measurement of the W boson mass using ≈200 pb-1 of CDF Run II data. With 63,964 W→eν candidates and 51,128 W→μν candidates, we measure MW = 80413 34 (stat) 34 (syst) MeV/c2. With a total uncertainty of 48 MeV/c2, this represents the single most precise MW measurement to date.
     Measurement Technique

    The W boson mass is extracted from a template fit to the transverse mass, transverse momentum and transverse missing energy distribution. We use a fast Monte Carlo simulation to predict the lineshape of the template distribution. These lineshape predictions depend on a number of physics and detector effects which we constrain from control samples or simulation. Important detector effects include external bremsstrahlung and ionization energy loss in the detector material, tracker momentum scale, calorimeter energy scale and resolutions of both detectors. Important physics effects include internal QED radiation, the intrinsic W boson transverse momentum and the proton parton distribution functions.

     Momentum Scale Calibration

     Energy Scale Calibration

     Recoil Calibration

     Production and Decay Model

     Additional W Mass Fits

    Charged Lepton Fits
    Neutrino Fits
     Uncertainty Tables

    Transverse Mass

    Transverse Momentum

    Transverse Missing Energy

     New MW vs Mtop Plots (Summer 2006 + New CDF W Mass)