Z + γ in 5/fb at CDF

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

Authors:
Blessed: February 11, 2010 July 15, 2010 June 23, 2011
Data: Run II, 5/fb (ee, μμ )

Introduction
Summary of Results

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 (h₃^Z,h₃^γ,h₄^Z,h₄^γ) 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
h₃^Z	[-0.024,0.027]	< 0.029
\|h₄^Z\|	< 0.0013	< 0.0015
h₃^γ	< 0.026	< 0.029
h₄^γ	[-0.0012 , 0.0013]	< 0.0016

Limits, (Λ = 1.5 TeV):

	Observed	Expected
h₃^Z	[-0.020, 0.021 ]	< 0.023
h₄^Z	< 0.0009	< 0.0010
h₃^γ	[-0.022, 0.020 ]	< 0.023
\|h₄^γ\|	< 0.0008	< 0.0010

Neutrino AGC Limit Results

	Znunu_controlreg_comp
	Photon Et distribution, data vs. our prediction, control region.
	pdf
	Znunu_signal_comp
	Photon Et distribution, neutrino data vs. our prediction, signal region.
	pdf eps
	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
h₃^Z	[-0.034,0.033]	< 0.036
h₄^Z	[-0.0015, 0.0016]	< 0.0017
h₃^γ	[-0.034,0.033]	< 0.036
h₄^γ	[-0.0017, 0.0016]	< 0.0017

	data_vs_pred
	Photon Et distribution, data vs. our prediction, control region.
	pdf
	data_vs_pred_v2
	Photon Et distribution, data vs. our prediction, signal region.
	pdf eps
	templates
	Expected photon Et distributions for SM (black) and for anomalous couplings (red and blue). Expected background is shown as solid histograms.
	pdf eps
	template_w_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
	Invariant mass distribution for combined electronic and muonic decays of Z bosons.
	eps
	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
h₃^Z	[-0.024,0.027]	< 0.029
\|h₄^Z\|	< 0.0013	< 0.0015
h₃^γ	< 0.026	< 0.029
h₄^γ	[-0.0012 , 0.0013]	+/- 0.0016

Limits, (Λ = 1.5 TeV):

	Observed	Expected
h₃^Z	[-0.020, 0.021 ]	< 0.007
h₄^Z	< 0.0009	< 0.0010
h₃^γ	[-0.022, 0.020 ]	< 0.023
\|h₄^γ\|	< 0.0008	< 0.0010

	logli_combo_1200
	One-dimensional log-likelihood limit plots showing limits, combination.
	pdf eps
	data_2d_1200_combo_Zgg
	Two-dimensional limit plot, combination.
	pdf eps
	data_2d_1200_combo_ZZg
	Two-dimensional limit plot, combination.
	pdf eps
	logli_combo_1500
	One-dimensional log-likelihood limit plots showing limits, combination.
	pdf eps
	data_2d_1500_combo_Zgg
	Two-dimensional limit plot, combination.
	pdf eps
	data_2d_1500_combo_ZZg
	Two-dimensional limit plot, combination.
	pdf eps