devika's blog

During the last W meeting both me and Jinlong presented Background Estimation for run 13 period 1.
Then we saw that for both W+ and W- Embedded MC W->e+ and W->e- are not properly fitting with data sample. (in both mine and Jinlong's analysis) As the plots shows below there's this gap between MC and data (Red dashed line and black solid line), which significantly shows between the region of 20<ET<35 GeV.

This Basically indicates that we are underestimating some type of BG (one or more) .This is very clear compared to run 12 BG estimation plots.

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Used data set of lumi 119.05 pb-1(st-WE, 120.67) and embedding sample we produced fro run 13 period one.

Embedding Total Events : Wplus -136589, Wminus - 43703, Z - 30945
Used same Analysis cut used in run 12
Below are the plots:

BG for 4 Eta bins

BG for 4 Eta bins
W-

Within Complete Barrel ETA region,

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NOW what is NOT very clear is that which types of BG that we are underestimating. Since W-tau and Z BG are very samll it is more likely to be QCD BG. But looking at the BG ratio as a percentage to raw yeilds and comaring to run 12 the differences are not significant.

W-

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NOW thinking of what is the BIG difference in run 13 compare to run 12, run 13 data sample is more dominant with QCD BG, compare to run 12 due to larger luminosities. Since we haven't treat specialy for run 13 data analysis , it seems good idea to calculate the BG for set of low luminosity (zdc rate) data sample and high luminosity (zdc rate) data sample separately.

I chossed list of 677 runs and calculate average ZDC. Then select highZDC runs with ZDC > <zdc>+0.5sigma and lowZDC runs with ZDC < <zdc>-) 0.5sigma

According to the BG now its clear that

We are UNDERESTIMATING BG for high luminosity runs

TOTAL BG

BG for 4 Eta bins

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QCD BG

Normalization Factor = (W yield (3 other BG subtracted) - W signal MC yield ) / nominal QCD BG yield (Z BG subtracted)

W+