ZRecoil
From ATLAS-TRIUMF
Contents |
[edit] Motivation
In many models, for example SUSY and 
decays, there is a high energy resonance that decays into two particles where one of the final state particles is a Z boson. For early data, it is expected that the muon energy and resolution will be better understood than the missing transverse energy or Jet energy scale. This means that the Pt of the Z0 boson will be will be both better understood in term of the systematic uncertainty, and is much less likely to have a hardware problem or detector modeling problem that can cause a false signal.
[edit] Analysis Strategy
The Z Recoil Analysis is a generic search for new physics that decays into a 
using the Pt spectrum in of the reconstructed Z0 boson. The strategy of this analysis is to select a clean sample of Z0 bosons, and then use the Pt spectrum as a discriminate to identify signal. The Pt spectrum can be used in a fit or used in a cut based analysis to determine the number of signal events. The side bands in the Z0 mass distribution can be used as control samples for the QCD backgrounds. One can also place additional cuts on the events to further classify the event and thereby reduce the amount of Standard Model background events with Z0's in them. In the work presented here, we use a 
MC as a bench mark for the signal.
[edit] Analysis Results
The results of the analysis can be found in this Link.
[edit] Discussion
Figure 8 (page 19) shows that the Z0 Pt and the Ht spectrum are strongly correlated. Comparing the significance and the signal/background plots of the Z0 Pt from Figure 18 on page 29 and Figure 9 on page 20 one can see that for a cut based analysis, the Z0 Pt method has a similar significance to the Ht method with a higher purity. In addition, the Z0 Pt allows extra cuts that can be used to reduce the backgrounds in the Pt spectrum (see Figure 14 on page 25).
