Measurement of the W Boson Mass with 2.2/fb of Data at CDF II

 
Bodhitha Jayatilaka, Ashutosh Kotwal, Ravi Shekhar, Siyuan Sun, Yu Zeng
Duke University
Oliver Stelzer-Chilton
TRIUMF
Larry Nodulman
Argonne National Laboratory
Daniel Beecher, Ilija Bizjak, Mark Lancaster, Sarah Malik, Tom Riddick, David Waters
University College London
Christopher Hays, Peter Renton
University of Oxford
Contact authors


MW = 80387 ± 19 MeV/c2
Phys. Rev. Lett. 108, 151803 (2012)
 
  • Abstract
  • Measurement Technique
  • Momentum Scale Calibration
  • Energy Scale Calibration
  • Recoil Calibration
  • Backgrounds
  • W Mass Fits
  • Uncertainty Tables
  • Future Projection
  • New MW vs Mtop Plots

  • Winter 2012 Conference Note


  •  

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     Abstract

    We present a measurement of the W boson mass using 2.2 fb-1 of CDF Run II data. With 470,126 W→eν candidates and 624,708 W→μν candidates, we measure MW = 80387 ± 19 MeV/c2. This represents the most precise measurement of the W boson mass 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

    • J/Ψ→μμ scale vs <1/pT(μ)> fit:
    • Υ(1S)→μμ (non beam-constrained tracks) scale fit:
    • Υ(1S)→μμ (beam-constrained tracks) scale fit:
    • Z→μμ mass fit:
    • Momentum scale summary:
     
     
     Energy Scale Calibration

    • Energy scale tuning from E/p spectrum from W electrons:
    • Radiative material tuning from E/p spectrum from W electrons:
    • Energy scale tuning from E/p spectrum from Z electrons:
    • Radiative material tuning from E/p spectrum from Z electrons:
    • Z→ee mass fit:
     
     
     Recoil Calibration

    Z recoil tuning (16,134 Z→ee and 59,738 Z→μμ Events)

    Mean of η balance vs ZpT: Z→ee:
    Mean of η balance vs ZpT: Z→μμ:

    RMS of η balance vs ZpT: Z→ee:
    RMS of η balance vs ZpT: Z→μμ:

    RMS of ξ balance vs ZpT: Z→ee:
    RMS of ξ balance vs ZpT: Z→μμ:

    Z recoil validation

    Hadronic recoil uT: Z→ee:
    Hadronic recoil uT: Z→μμ:

    W recoil validation

    u||: W→eν:
    u||: W→μν:
  • u: W→eν:
  • u: W→μν:
    Hadronic recoil pT (uT): W→eν:
    Hadronic recoil pT W→μν:

     
     
     Backgrounds

    Muons


    Electrons

     
     
     W Mass Fits

    Transverse Mass Fits (muons)

    (electrons)

    Charged Lepton Fits (muons)

    (electrons)

    Neutrino Fits (muons)

    (electrons)
     
     
     Uncertainty Tables

    Transverse Mass


    Transverse Momentum


    Transverse Missing Energy

     
     
     Future Projection
     
     
     New MW vs Mtop Plots (Summer 2011 + New CDF W Mass)

    • Pete Renton (LEP EWKWG): (eps) Constraint on the mass of the higgs boson: MH = 90+29-23 GeV/c2, MH < 145 GeV/c2 @95% CL
      (previously: MH = 92+34-26 GeV/c2, MH < 161 GeV/c2 @95% CL)
      The LEP Electroweak Working Group
    • Comparisons of MW. New world average of MW = 80390 ± 16 MeV