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An Improved W Boson Mass Analysis with CDF Run II Data 

Dan Beecher ^{(c)},
Ilija Bizjak ^{(c)},
Chris Hays ^{(d)},
Bo Jayatilaka ^{(b)},
Ashutosh Kotwal ^{(b)},
Mark Lancaster ^{(c)},
Sarah Malik ^{(c)},
Emily Nurse ^{(c)},
Larry Nodulman ^{(a)},
Peter Renton ^{(d)},
Tom Riddick ^{(c)},
Ravi Shekar ^{(b)},
Oliver StelzerChilton ^{(d)},
Dave Waters ^{(c)},
Yu Zeng ^{(b)}

^{(a)}Argonne National Laboratory,
^{(b)}Duke University,
^{(c)}University College London,
^{(d)}University of Oxford

The CDF collaboration has previously
measured the mass of the W boson on 200 pb^{1} of the
Tevatron Run II data. The plots presented here are preliminary
comparisons of the data and simulation using 2.3 fb^{1} of
the Tevatron Run II data for high p_{T} muon and 2.4
fb^{1} for high p_{T} electron channels.
All the Z and W mass fits are blinded by a preselected
unknown offset in the range of [75MeV, 75MeV], which is different
for Z and W bosons. The fit ranges are marked by arrows pointing to
the lower and upper edges of the fit range. The fit plots quote the
statistical uncertainty and the χ^{2} value of the fit.

Instantaneous luminosity
Instantaneous Luminosity profile 
∑E_{T} 


Left:
The comparison of the instantaneous luminosity distributions in
Z→e^{+}e^{+} decays for the sample used in
the published result and the 2.4 fb^{1} data. The average
instantaneous luminosity in the 2.4 fb^{1} data is 70 x
10^{30} s^{1} cm^{2}.

Right:
The comparison between the distributions of
∑E_{T}, the sum of the E_{T} deposits in the
calorimeter, in data and simulation: the distributions are compared
separately for events with instantaneous luminosity larger and lower
than the average instantaneous luminosity, showing that the
simulation captures the luminosity dependence of the distribution.

Z→μ^{+}μ^{} invariant mass distribution
Left:
The Z mass fit to the invariant mass of Z→μ^{+}μ^{} decays.

Right:
The comparison of the statistical uncertainties of the fitted Z
mass: the statistical uncertainty for the published result (200
pb^{1}), the expected statistical uncertainty obtained by
scaling the published result by the square root of the ratio of
integrated luminosites, and the statistical uncertainty obtained
from the presented preliminary fit. The fit uncertainties show that
the muon momentum resolution in the 2.3 fb^{1} dataset is
comparable to that of the data used in the published result.

Z→e^{+}e^{} invariant mass distribution
Left:
The Z mass fit to the invariant mass of Z→e^{+}e^{} decays.

Right:
The comparison of the statistical uncertainties of the fitted Z mass:
the statistical uncertainty for the published result (200
pb^{1}), the expected statistical uncertainty obtained by
scaling the published result by the square root of the ratio of
integrated luminosites, and the statistical uncertainty obtained
from the presented preliminary fit. The fit uncertainties show that
the electron energy resolution in the 2.4 fb^{1} dataset is
comparable to that of the data used in the published result.

Z→e^{+}e^{} invariant mass plot using track information only
Left:
The Z mass fit to the invariant mass of
Z→e^{+}e^{} decays, using track information
of the electrons only.

Right:
The comparison of the statistical uncertainties of the fitted Z mass:
the statistical uncertainty for the published result (200
pb^{1}), the expected statistical uncertainty obtained by
scaling the published result by the square root of the ratio of
integrated luminosites, and the statistical uncertainty obtained
from the presented preliminary fit. The fit uncertainties show that
the electron tracking resolution in the 2.4 fb^{1} dataset is
comparable to that of the data used in the published result.

W→μν transverse mass distribution
Left:
The W mass fit to the transverse mass of W→μν decays.

Right:
The comparison of the statistical uncertainties of the fitted W
mass: the statistical uncertainty for the published result (200
pb^{1}), the expected statistical uncertainty obtained by
scaling the published result by the square root of the ratio of
integrated luminosites, and the statistical uncertainty obtained
from the presented preliminary fit. The fit uncertainties show that
the degradation of the recoil resolution in the 2.3 fb^{1}
dataset has not significantly degraded the W transverse mass
resolution.

W→eν transverse mass distribution
Left:
The W mass fit to the transverse mass of W→ eν decays.

Right:
The comparison of the statistical uncertainties of the fitted W
mass: the statistical uncertainty for the published result (200
pb^{1}), the expected statistical uncertainty obtained by
scaling the published result by the square root of the ratio of
integrated luminosites, and the statistical uncertainty obtained
from the presented preliminary fit. The fit uncertainties show that
the degradation of the recoil resolution in the 2.4 fb^{1}
dataset has not significantly degraded the W transverse mass
resolution.

W→eν E/pc distribution
Left:
The fit to the E/pc distribution of W→ eν decays
for the absolute scale of the energy measurement.

Right:
The comparison of the W mass uncertainties due to the statistical
uncertainty of the absolute energy scale fit : this uncertainty for
the published result (200 pb^{1}), the expected uncertainty
obtained by scaling the published result by the square root of the
ratio of integrated luminosites, and the uncertainty obtained from
the presented preliminary fit. The fit uncertainties show that the
electron tracking and energy resolutions in the 2.4 fb^{1}
dataset are comparable to that of the data used in the published
result.

J/ψ→μ^{+}μ^{} invariant mass distribution


Left:
The fit to the invariant mass distribution of
J/ψ→μ^{+}μ^{} decays for the
absolute scale of the momentum measurement. The fit is performed in
8 bins of the average inverse muon momentum of the two muons, the
example plot shown is for the highest momentum bin with significant
statistics (0.1 < <1/p_{T}^{μ}> < 0.15
(GeV/c)^{1}, roughly corresponding to average muon momenta
of 6.7 < <p_{T}^{μ}> < 10 GeV/c).

Right:
The comparison of the W mass uncertainties due to the statistical
uncertainty of the absolute momentum scale fit in the highest
momentum bin: this uncertainty for the published result (200
pb^{1}), the expected uncertainty obtained by scaling the
published result by the square root of the ratio of integrated
luminosites, and the uncertainty obtained from the presented
preliminary fit. The fit uncertainties show that the muon momentum
resolution in the 2.3 fb^{1} dataset is comparable to that
of the data used in the published result.

Υ(1S)→μ^{+}μ^{} invariant mass distribution
Left:
The fit to the invariant mass distribution of
Υ(1S)→μ^{+}μ^{} decays for the
absolute scale of the momentum measurement.

Right:
The comparison of the W mass uncertainties due to the statistical
uncertainty of the absolute momentum scale fit: this uncertainty for
the published result (200 pb^{1}), the expected uncertainty
obtained by scaling the published result by the square root of the
ratio of integrated luminosites, and the uncertainty obtained from
the presented preliminary fit. The fit uncertainties show that the
muon momentum resolution in the 2.3 fb^{1} dataset is
comparable to that of the data used in the published result.
