Unfolding Study
07/06/12
1
RooUnfold
Using the RooUnfold 1.1.1
http://hepunx.rl.ac.uk/~adye/software/unfold/RooUnfold.html
 In this study we make response matrix from MADGRAPH MC and use it to unfold the
CMS Data
Plots we are interested are rapidity of Z and jet in Z+1jet events i.e.
 Yz, Yjet, different of Yz and Yjet, and sum of Yz and Yjet
 The unfolding methods are
 Bayes with number of iteration = 4
 Svd with ktern =15 (total number of bins) i.e. just inverts matrix
 Bin by Bin
 Also we checking the error by running the “toy” experiments, where the statistics of the
response matrix are varied
 Closure test using pythia dataset?????????

2
Response Matrix
3
|Y of Z|
Bayes
Svd
Bin by Bin
The corrections for all 3 methods are small.
 The corrections are almost the same for all 3 methods.

4
|Y of jet|
Bayes
Svd
Bin by Bin
The corrections are bigger than that of Z but still considerably small.
 The corrections are almost the same for all 3 methods.

5
0.5|Yz+Yjet|
Bayes

Svd
Bin by Bin
Y sum again shows the small and consistent corrections for all methods.
6
0.5|Yz-Yjet|
Bayes
Svd
Bin by Bin
Y diff shows the small corrections but not the last two bins.
 There big corrections in last two bin might be from low statistic (big errors).

7
Error Test

“Toy” experiments is used to vary the statistic of response matrix with below code:
unfold.SetNToys(1000);
TVectorD errVector = unfold.ErecoV(3);
unfold.PrintTable (cout, hGen);
ErrVector.Print("all");

The result from the code is random number in the table below
Vector (15) all is as follows
|
1 |
-----------------0 |163.426
1 |151.223
2 |137.28
3 |117.141
4 |95.0418
5 |72.9619
6 |53.6503
7 |37.5361
8 |24.1118
9 |13.5451
10 |5.27294
11 |0
12 |0
13 |0
14 |0
8
Keng's Comments
1. It seem that we have small corrections from Unfolding except some bins that might have small
entries (big error bar).
2. The correction also look the same for all methods. Should we conclude that results are
independent of the methods?
3.The “toy” experiment gives us some result. Does this prove that error is correct?
Could you explain more why this “toy” experiment can be use to test error?
4.There is the problem for the Closure test. The MC I am using are
/DYToMuMu_M-20_TuneZ2_7TeV-pythia6/Fall11-PU_S6_START44_V9B-v1/AODSIM
There are only 2148325 events. There are not many gen jets in the datasets.
After mass cut (76-106), Z pt cut (40) and number of jet is 1, there are only 4 events left for gen
jets. Should we use other MC for this?
9