Measurement of Z Forward-backward Asymmetry

Authors: Jedong Lee, Gilles De Lentdecker, Kevin McFarland
Last Updated: May 14th, 2006

Abstract

We present a measurement of the Z boson forward-backward asymmetry of the process ppbar -> &gamma*/Z + X -> e+e- + X, in the region where the dielectron invariant mass is larger than 50 GeV/c^2. The measurement uses 364/pb of CDF Run II data. The method of matrix inversion is used to correct for the distortion in the measurement caused by the detector resolution and photon radiation in the final state.

Event Selection

Variable Central Plug
Fiducial Fid = 1 or 2 1.18 < |eta| < 3.0
ET > 25 GeV > 25 GeV
|Track Z0| <= 60 cm N/A
PT > 15 GeV (ET < 100 GeV),
> 25 GeV (ET > 100 GeV)
N/A
Ehad/Eem <= 0.055 + 0.00045 * E <= 0.05 + 0.026 * log(E/100)
Isolation(GeV) <= 3 + 0.02 ET <= 1.6 + 0.02 ET
E/p <= 2.5 + 0.015 ET (ET < 100 GeV) N/A
|delta X| < 3 cm N/A
|delta Z| < 5 cm N/A
Lshr < 0.2 N/A
PEM chi2 3x3 N/A 25
Charge Opposite charge for CC events.
For the CP events, plug electron charge is assumed to be the opposite
to the central electron.
Mee > 50 GeV

Tables and Plots

Dielectron invariant mass distribution
of data and MC.
Energy scale correction is applied. 50-120 GeV. .gif
Dielectron invariant mass distribution
of data and MC.
Energy scale correction is applied. 120-600 GeV. .gif
Dielectron invariant mass distribution
of data and MC.
Energy scale correction is applied. 500-120 GeV, in ratio. .gif
Dielectron invariant mass distribution
of data and MC.
Energy scale correction is applied. 120-600 GeV, in ratio. .gif
Response matrix .gif
Unfolded AFB.
Agreement with the LO SM calculation is
chi2/ndof = 10.9/12. .gif
Unfolded AFB.
Residual.
.gif
Unfolded AFB.
Zoomed into the Z pole.
.gif
Unfolded AFB.
Zoomed into the Z pole.
Residual.
.gif
Background estimation. .gif
Raw and unfolded AFB in 12 bins. .gif
Summary of uncertainties. .gif

 

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