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

Abstract

This paper presents an updated 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 directly from the data. The size of the data sample corresponds to an integrated luminosity of 191 pb−1. In the absence of any significant excess beyond the SM expectation, upper limits are set in the context of the constrained minimal supersymmetric standard model.

Approved Plots from SUS-11-012 ( click on plot to get .pdf )

Figure Abbreviated Caption
Fig1a.png JZB distributions in data (points) and Monte Carlo simulation (stacked histograms), in the e+e- and μ+μ- sample
[ EPS ]
Fig1b.png JZB distributions in data (points) and Monte Carlo simulation (stacked histograms), in the e±μ sample
[ EPS ]
Fig2a.png JZB distribution in the e+e- and μ+μ- data sample, and in the e±μ data sample
[ EPS ]
Fig2b.png Comparison of the predicted and observed JZB distributions in the e+e- and μ+μ- data sample. The background prediction has been fitted to display the ±σ uncertainty band based on Poisson statistics.
[ EPS ]
Fig3a.png Ratio of observed to predicted number of events in bins of JZB for SM MC
[ EPS ]
Fig3b.png Ratio of observed to predicted number of events in bins of JZB for data
[ EPS ]

Re-interpretation in terms of simplified models

The language of simplified models has been introduced recently (see e.g. here and here) to establish an efficient communication channel between the LHC experiments and the theory communities who have proposed a general set of simplified models with which LHC data can be interpreted. A similar approach has been taken before in the hadronic channel with 2010 data -- see here.

The above results have been re-interpreted in terms of the simplified models given in the following table. The signal efficiencies as a function of the mass parameters of the simplified model are also given below, together with upper limit plots on the production cross section. The data for these plots are also available as a ROOT file: T5zz_jzb.root.

The signal contamination to the negative JZB region has been taken into account for the computation of the limits.

Figure Abbreviated Caption
Simplified model topology "T5zz". m(chi20)=0.5* (m(gluino)+m(LSP)). The Z decay naturally
Signal efficiencies for T5zz, for the "low JZB" selection. Efficiency normalized to the events that contains at least one Z to leptons.
Signal efficiencies for T5zz, for the "high JZB" selection. Efficiency normalized to the events that contains at least one Z to leptons.
Upper limit on production cross section, for T5zz, assuming a branching ratio of 1. For each point, the result of the "best" selection (i.e. the minimal value for the upper limit) is taken. Superimposed are 95% CL exclusion contours, assuming a "reference SUSY cross section", for decoupled squarks: m(~q)>>m(~g).

Link to SUS-11-012 PAS in CDS

See also the PAS it is based upon: SUS-10-010

-- FredericRonga - 08-Jun-2011

Topic attachments
I Attachment History Action Size Date Who Comment
Unknown file formateps Fig1a.eps r1 manage 44.4 K 2011-06-08 - 13:00 FredericRonga  
PDFpdf Fig1a.pdf r1 manage 12.4 K 2011-06-08 - 13:00 FredericRonga  
PNGpng Fig1a.png r1 manage 428.4 K 2011-06-08 - 13:00 FredericRonga  
Unknown file formateps Fig1b.eps r1 manage 24.0 K 2011-06-08 - 13:00 FredericRonga  
PDFpdf Fig1b.pdf r1 manage 6.4 K 2011-06-08 - 13:01 FredericRonga  
PNGpng Fig1b.png r1 manage 346.3 K 2011-06-08 - 13:01 FredericRonga  
Unknown file formateps Fig2a.eps r1 manage 15.1 K 2011-06-08 - 13:01 FredericRonga  
PDFpdf Fig2a.pdf r1 manage 8.9 K 2011-06-08 - 13:01 FredericRonga  
PNGpng Fig2a.png r1 manage 437.4 K 2011-06-08 - 13:01 FredericRonga  
Unknown file formateps Fig2b.eps r1 manage 15.7 K 2011-06-08 - 13:02 FredericRonga  
PDFpdf Fig2b.pdf r1 manage 6.8 K 2011-06-08 - 13:02 FredericRonga  
PNGpng Fig2b.png r2 r1 manage 503.3 K 2011-06-08 - 13:04 FredericRonga  
Unknown file formateps Fig3a.eps r1 manage 11.7 K 2011-06-08 - 13:02 FredericRonga  
PDFpdf Fig3a.pdf r1 manage 5.5 K 2011-06-08 - 13:02 FredericRonga  
PNGpng Fig3a.png r1 manage 519.7 K 2011-06-08 - 13:03 FredericRonga  
Unknown file formateps Fig3b.eps r1 manage 11.8 K 2011-06-08 - 13:03 FredericRonga  
PDFpdf Fig3b.pdf r1 manage 28.7 K 2011-06-08 - 13:03 FredericRonga  
PNGpng Fig3b.png r1 manage 535.7 K 2011-06-08 - 13:03 FredericRonga  
Unknown file formatroot T5zz_jzb.root r1 manage 18.4 K 2011-09-13 - 14:21 MariarosariaDalfonso  
PDFpdf comparison_T5zz_JZB_xSec.pdf r1 manage 15.4 K 2011-09-30 - 10:53 Walten upper limit cross-section T5zz JZB
PNGpng comparison_T5zz_JZB_xSec.png r1 manage 39.4 K 2011-09-30 - 10:53 Walten upper limit cross-section T5zz JZB
PNGpng h_eff_T5zz_JZB_100.png r1 manage 12.1 K 2011-09-30 - 10:52 Walten efficiencies of JZB, T5zz, high JZB
PDFpdf h_eff_T5zz_JZB_50.pdf r1 manage 15.1 K 2011-09-30 - 10:51 Walten efficiencies of JZB, T5zz
PNGpng h_eff_T5zz_JZB_50.png r1 manage 11.6 K 2011-09-30 - 10:51 Walten efficiencies of JZB, T5zz
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Topic revision: r10 - 2011-09-30 - Walten
 
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