Search for Physics Beyond the Standard Model in Z + MET + Jets events at the LHC

Abstract

This paper presents an update of a search for Physics beyond the Standard Model in final states with a Z boson, jets and missing transverse energy. The Jet-Z Balance method is used to estimate the total background expected in the signal region from data control samples. The size of the data corresponds to an integrated luminosity of 2.1 fb−1. In the absence of any significant excess beyond the SM expectation, upper limits are set in the context of simplified models of supersymmetry, taking into account signal contribution to the control samples.

Approved Plots from SUS-11-019 ( click on plot to get .pdf )

Figure	Abbreviated Caption
	Dilepton invariant mass distribution in preselected events, for same-flavour (ee or mumu) pairs in data (points) and in MC simulation (histograms). The dashed vertical lines indicate the signal and side-band regions.
	Dilepton invariant mass distribution in preselected events, for opposite-flavour (emu) pairs in data (points) and in MC simulation (histograms). The dashed vertical lines indicate the signal and side-band regions.
	JZB distribution in ZJets, TTbar and signal MC simulation scaled to 2.1fb-1, after preselection and dilepton invariant mass requirement. The signal distribution corresponds to the SUSY LM4 scenario. Events in the tail are affected by the pile-up reweighting of MC simulation.
	Data versus MC comparison of the JZB distribution for the same flavor (ee or mumu) di-leptons consistent with mZ mass.
	Data versus MC comparison of the JZB distribution for the opposite flavor (emu) di-leptons consistent with mZ mass.
	Data versus MC comparison of the JZB distribution for the same flavor (ee or mumu) di-leptons in the mZ mass sidebands.
	Data versus MC comparison of the JZB distribution for the opposite flavor (emu) di-leptons in the mZ mass sidebands.
	Comparison of the JZB distributions in the signal region and the control regions in TTbar MC simulation.
	Ratio between the JZB distribution in each control region and that in the signal region. The assigned systematic error is also shown.
	MC expected observed event yield, compared with the estimated background event yield (MC closure test) in a SM only null hypothesis.
	Ratio between observed and predicted JZB distributions in MC, in the SM only null hypothesis. The errors reflect the statistical uncertainty of the corresponding MC samples.
	MC expected observed event yield, compared with the estimated background event yield (MC closure test) in a NP signal + background hypothesis.
	Ratio between observed and predicted JZB distributions in MC simulation, in the NP signal + background hypothesis. The errors reflect the statistical uncertainty of the corresponding MC samples.
	Comparison between the predicted and observed JZB distributions in the CMS data. The predicted distribution has been fitted to display 1 sigma statistical uncertainty bands.
	Ratio of observed over predicted event yields in the data. The error bars represent the corresponding statistical uncertainty.
	SMS signal efficiency (including acceptance) in the mGluino, mLSP parameter space, for the JZB>50 GeV region.
	SMS signal efficiency (including acceptance) in the mGluino, mLSP parameter space, for the JZB>100 GeV region.
	SMS signal efficiency (including acceptance) in the mGluino, mLSP parameter space, for the JZB>150 GeV region.
	95% CL upper limits on the cross-section of the inclusive Z boson decay mode in the mGluino,mLSP SMS parameter space. In each point, the best expected limit from the low-, mid-, and high- JZB regions is used. The exclusion curves for reference cross-sections are also shown in this plot.
	Map of the JZB region giving the best limit in each point of the parameter space.

Link to SUS-11-019 PAS in CDS

-- KostasTheofilatos - 11-Nov-2011