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QCD Background substraction

Updated on Tue, 2014-06-10 16:56. Originally created by devika on 2014-06-06 11:58.

Barrel W:

 

The significant Background to the W->ev process is cmonig from QCD processes where a jet imitates an isolated e  candidate. This background is estimated by determining a data-driven QCD background distribution as a function of EeT  (data-driven QCD background "shape"). 

 
QCD BG ->>>>************Estimated by determining a data-driven QCD BG distribution as a function of ET.

This is estimate as explaing in the following steps. 

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Steps
  1) Select sample of events interest with an isolated e+/e- candidate passing all isolation cuts but fails signed pt balance cuts.
 
  (this sample is dominated by QCD multi jet BG where one jets "fakes" an e+/e- and the event is rejected due to reconstructed jet opposite in phi. )

Ex, Events of run13 period 1 data sample which fails signed pt balance cut.

 

 2) This  sample should also contain some Z->e+e- events , so they should be remove as follows.

 

 Veto identified Z-> e+e- events from QCD BG distribution.  [ already substracted in above histogram ]

 ******remove any events with an isolated cluster and a jet contains another 2X2 ETOW/BTOW cluster with E2X2T > 0.5.PTjet and the invarient mass of the lepton candidate cluster and the jet is with in [70,140] GeV range *******.

 

3 ) If there are any remaining  Z bachground   shoud remove  using z->e+e- MC samples.  

4) After the 3 backgrounds being substracted from the W yeild the data-driven QCD background shape can be normalized to the remaining yield to obtain this  nal contribution to the background. 

 

macro

 
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