Top Quark Mass at CDF

1
Top Quark Mass at CDF
Wojciech Fedorko, University of Chicago on behalf
of the CDF collaboration
Why measure the top quark mass
Jet energy uncertainty
Top quark mass constrains Standard Model Higgs
mass

• Important but difficult measurement
• Complicated events
• Many measured objects to figure out with correct
  assignments
• Different backgrounds

Jet Energy Scale is one of the main challenges
Lepton Jets channel
Matrix Element Method
Template Method
mt template

• Use the Standard Model (matrix element) for each
  event to determine the most likely values of Mtop
  and the jet energy scale.
• All combinations are used.

In the detector

• Compare reconstructed top mass and W mass shapes
  from Monte Carlo to shapes in data

At the collision point
b
q
t
q
q
W-
b
t
q
e,µ
W
?
Mtop 174.1 2.9 GeV
The single best top quark mass measurement in the
world!
e, µ

• Good signal to
• background ratio
• One fully reconstructed top (Golden Channel)

missing energy
We can calibrate jet energy shifts in-situ using
hadronic W peak
Mtop 173.4 2.8 GeV
Dilepton channel Matrix Element Method
In the detector
At the collision point

• Excellent purity
• Poor statistics
• Only one missing energy for two neutrinos

• Determine the most likely value of top mass
  weighted by the matrix element for given measured
  quantities

e, µ
Mtop 164.5 5.5 GeV
e, µ
missing energy
Impact of CDF measurements
Summer 05
Spring 06
Summer 04
MtopCDF 172.4 2.6 GeV
MtopWorld 172.5 2.3 GeV
First Run II in All Hadronic !
Dramatic improvement to the constraint on the
Higgs mass
Single Best !!