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Background_Estimation_run13_period1

Updated on Mon, 2014-08-11 08:57. Originally created by devika on 2014-06-09 15:53.
Channel Estimation
W->tau

Branching Ratio ~ 11% , semi-leptonically ~13%

Experimentally indistinguishable from W-eν decay

Use PHYTIA+GEANT embedded simulation sample

In asymmetry  calculation contribution to the W yield is treat as signal
Z->e+e

              Background is also significant because STAR is not hermetic.

Use PHYTIA+GEANT embedded simulation sample 
second endcap

EEMC has coverage 1.09<η<2 and helps to reject QCD BG with detecting jet opposite in phi. 

Since no Endcap on East side of STAR  events with opposite jet of -2<η<-1.09 will be good signal event 

Run the analysis twice with and without EEMC as veto
QCD

Events which become good signal event by one jet escape detection.

use data-driven QCD BG shape as a function of ET to determine.

Scaling Luminosity Of MC to data Luminosity:

Lumi of MC = MC events / cross section

Lumi normalization factor = Data Lumi / Lumi of MC

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SECOND ENDCAP BACKGROUND

Strategy 
Calculate the BG events that are rejected by the real EEMC of STAR for each eta bin and assumed to be same as the BG that would have been rejected by the fictitious "second endcap"

Method:

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1) Run the whole analysis 2 times,  First using ETOW  as a veto in the near-side and sign pt balance cuts and then without using the ETOW in these cuts.
 
2) The difference in the EeT distribution between these 2 passes of the analysis is the background rejected by using the real EEMC
3) Assume this as the same background that would have been rejected by the fictitious end cap
 
4) Background events rejected by the real EEMC which are measured in the positive Eta bins correspond to BG events that would be removed from the signal yield in the negative Eta bin by a fictitious EEMC on the east side of STAR
5) Any Z contamination in this BG sample should remove using Z MC sample 



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