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Measurement of the Forward-Backward Charge Asymmetry from W --> e nu Production in p anti-p Collisions at s**(1/2) = 1.96 TeV

D. Acosta, The CDF Collaboration

TL;DR

This study measures the forward-backward charge asymmetry in W -> e nu production in pbar-p collisions at sqrt(s) = 1.96 TeV using 170 pb^-1 of data from the CDF II detector. By constructing A(eta_e) and separating events into two electron ET regions, the analysis mitigates neutrino kinematic ambiguities and enhances sensitivity to the u/d quark PDF ratio at x > 0.3. The observed asymmetry is corrected for charge misidentification and backgrounds, and the results are compared to NLO RESBOS predictions with contemporary PDFs, providing constraints for future global PDF fits and improving PDF-related systematic uncertainties in precision measurements. The findings contribute to a more accurate mapping of parton momentum distributions, with implications for cross-section calculations and W mass determinations at hadron colliders.

Abstract

We report a measurement of the forward-backward charge asymmetry of electrons from W boson decays in p anti-p collisions at s**(1/2) = 1.96 TeV using a data sample of 170 pb-1 collected by the Collider Detector at Fermilab. The asymmetry is measured as a function of electron rapidity and transverse energy and provides new input on the momentum fraction dependence of the u and d quark parton distribution within the proton.

Measurement of the Forward-Backward Charge Asymmetry from W --> e nu Production in p anti-p Collisions at s**(1/2) = 1.96 TeV

TL;DR

This study measures the forward-backward charge asymmetry in W -> e nu production in pbar-p collisions at sqrt(s) = 1.96 TeV using 170 pb^-1 of data from the CDF II detector. By constructing A(eta_e) and separating events into two electron ET regions, the analysis mitigates neutrino kinematic ambiguities and enhances sensitivity to the u/d quark PDF ratio at x > 0.3. The observed asymmetry is corrected for charge misidentification and backgrounds, and the results are compared to NLO RESBOS predictions with contemporary PDFs, providing constraints for future global PDF fits and improving PDF-related systematic uncertainties in precision measurements. The findings contribute to a more accurate mapping of parton momentum distributions, with implications for cross-section calculations and W mass determinations at hadron colliders.

Abstract

We report a measurement of the forward-backward charge asymmetry of electrons from W boson decays in p anti-p collisions at s**(1/2) = 1.96 TeV using a data sample of 170 pb-1 collected by the Collider Detector at Fermilab. The asymmetry is measured as a function of electron rapidity and transverse energy and provides new input on the momentum fraction dependence of the u and d quark parton distribution within the proton.

Paper Structure

This paper contains 9 sections, 2 equations, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Detector Description
  3. Data Sets and Selection
  4. Measurement of the Charge Asymmetry
  5. Charge Misidentification
  6. Background Corrections
  7. $E_T$ dependence
  8. Systematic uncertainties
  9. Results

Figures (5)

  • Figure 1: The raw, uncorrected, charge asymmetry is plotted as a function of electron $\eta$.
  • Figure 2: The charge misidentification probability is plotted as a function of electron $\eta$.
  • Figure 3: The difference in charge misidentification probability of $e^+$ and $e^-$, $f_+(\eta) - f_-(\eta)$, is plotted as a function of electron $\eta$.
  • Figure 4: The fully corrected charge asymmetry is plotted as a function of electron $\eta$. Both statistical and total (statistical+systematic) uncertainties are shown.
  • Figure 5: The measured asymmetry, $A(|\eta_e|)$, is plotted and predictions from the CTEQ6.1M (solid) and MRST02 (dashed) PDFs are compared using a NLO RESBOS calculation. Both statistical and total (statistical+systematic) uncertainties are shown. The upper plot is for $25<E_T<35$ GeV. The lower plot is for $35<E_T<45$ GeV.