CDF Logo Z γ Limits on Neutral Anomalous Coupling in 5/fb of ppbar Collisions at √s=1.96 TeV CDF Logo

Contents

Abstract

We have measured (Z → l+l-)+γ production with central photons using electronic and muonicZ decays. We have also studied invisible (Z →νν )+γ using photons and missing transverse energy. A study of potential anomalous couplings between Z's and photons is performed. Limits are placed on the four CP-conserving couplings (h3Z,h3γ,h4Z,h4γ) using 5 fb-1 of data. This is the first measurement of its kind in Z → llγ events at CDF since an analysis performed using 1 fb-1 of electron candidate data and 2 fb-1 of muon candidate data; improvement is witnessed as this is a statistics-limited measurement.

Summary of Results

Limits on ATGC using 5/fb of (Z → l+l-)+γ and (Z →νν )+γ data.

Limits, (Λ = 1.2 TeV):

Observed Expected
h3Z [-0.018,0.020] +/- 0.024
|h4Z| < 0.0009 < 0.0011
h3γ [-0.022,0.021] +/- 0.023
h4γ [-0.0009 , 0.0010] +/- 0.0011
Limits, (Λ = 1.5 TeV):
Observed Expected
h3Z [-0.017, 0.016 ] +/- 0.018
h4Z [-0.0006, 0.0005] +/- 0.00065
h3γ [-0.017, 0.016 ] +/- 0.018
|h4γ| < 0.0006 < 0.00065

Neutrino AGC Limit Results

blessedPlots/Znunu_controlreg_comp Znunu_controlreg_comp

Photon Et distribution, data vs. our prediction, control region.

pdf
blessedPlots/Znunu_signal_comp Znunu_signal_comp

Photon Et distribution, neutrino data vs. our prediction, signal region.

pdf eps
blessedPlots/SM_expectation SM_expectation

Expected photon Et distributions for SM Z + γ (yellow). Expected background is shown as stacked histograms on top of signal.

pdf eps

Electron + Muon Combined AGC Limit Results

Limits (Λ = 1.2 TeV):
Observed Expected
h3Z [-0.034,0.033] < 0.036
h4Z [-0.0015, 0.0016] < 0.0017
h3γ [-0.034,0.033] < 0.036
h4γ [-0.0017, 0.0016] < 0.0017
blessedPlots/data_vs_pred_lowpt data_vs_pred

Photon Et distribution, data vs. our prediction, control region.

pdf
blessedPlots/data_vs_pred_v2 data_vs_pred_v2

Photon Et distribution, data vs. our prediction, signal region.

pdf eps
figures/templates templates

Expected photon Et distributions for SM (black) and for anomalous couplings (red and blue). Expected background is shown as solid histograms.

pdf eps
figures/templates_incl_data templates_incl_data

Expected and measured photon Et distributions for SM (black) and for anomalous couplings (red and blue). Expected background is shown as solid histograms.

pdf eps
combined_leptons combined_leptons

Invariant mass distribution for combined electronic and muonic decays of Z bosons.

eps
blessedPlots/MllVsMllg MllVsMllg

llγ vs. ll invariant mass distribution for combined electronic and muonic decays of Z bosons.

pdf eps

Electron + Muon + Neutrino Combined Results

Limits, (Λ = 1.2 TeV):
Observed Expected
h3Z [-0.018,0.020] +/- 0.024
|h4Z| < 0.0009 < 0.0011
h3γ [-0.022,0.021] +/- 0.023
h4γ [-0.0009 , 0.0010] +/- 0.0011
Limits, (Λ = 1.5 TeV):
Observed Expected
h3Z [-0.017, 0.016 ] +/- 0.018
h4Z [-0.0006, 0.0005] +/- 0.00065
h3γ [-0.017, 0.016 ] +/- 0.018
|h4γ| < 0.0006 < 0.00065
blessedPlots/logli_combo_1200 logli_combo_1200

One-dimensional log-likelihood limit plots showing limits, combination.

pdf eps
blessedPlots/data_2d_1200_combo_Zgg data_2d_1200_combo_Zgg

Two-dimensional limit plot, combination.

pdf eps
blessedPlots/data_2d_1200_combo_ZZg data_2d_1200_combo_ZZg

Two-dimensional limit plot, combination.

pdf eps
blessedPlots/logli_combo_1500 logli_combo_1500

One-dimensional log-likelihood limit plots showing limits, combination.

pdf eps
blessedPlots/data_2d_1500_combo_Zgg data_2d_1500_combo_Zgg

Two-dimensional limit plot, combination.

pdf eps
blessedPlots/data_2d_1500_combo_ZZg data_2d_1500_combo_ZZg

Two-dimensional limit plot, combination.

pdf eps

Contact, Legal Notices, and Fermilab Policy on Computing