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---+!! CMS Tutorial @ PKU -- From Zero to Expert

---+++ !!Upsilon Analysis Exercises

Main.ZhenHu, Main.FangzhouZhang, Sijin Qian

%BLUE% *Goal of this twiki* %ENDCOLOR%

This Twiki page presents a tutorial prepared for new CMS students at Peking University.
We assume the attendees to be familiar with basic C++ and ROOT.

%BLUE% *Acknowledgments* %ENDCOLOR%

CMS Group at Purdue University, Fermilab LPC, [[https://www.physics.purdue.edu/particle/ejterm/][EJTerm]]

Main.YuZheng, Main.ZoltanGecse, Main.NunoLeonardo, Main.IanShipsey


%TOC{title="Contents:"}%

---+ Introduction

In these Exercises we will measure the %ORANGE% *Upsilon resonance cross section* %ENDCOLOR%. 

The differential cross section is given by
%BEGINLATEX%
  \begin{displaymath}
\frac{d\sigma (pp \to \Upsilon(nS))}{dp_T} \times Br(\Upsilon(nS) \to \mu^{+}\mu^{-}) = \frac{N^{fit}_{\Upsilon(nS)}(p_T; {\cal{A}}, \epsilon)}{\int {\cal{L}} dt \cdot \Delta p_T}
  \end{displaymath}
%ENDLATEX%

The determination of the l.h.s is obtained from the r.h.s measured inputs: 
   * acceptance *A* (see [[#Exercise_2_Calculation_of_Accept][Exercise 2]]), 
   * efficiency *&#949;* (see [[#Exercise_3_Using_Tag_and_Probe_t][Exercise 3]]), 
   * fitted yield *N* (see [[#Exercise_4_Upsilon_Selection_and][Exercise 4]]), 
   * and luminosity *L*.

The implementation presented is based on the analysis of dimuon events, collected with the HLT_Mu3 trigger. The basic objects are tracker muons. 


---+ Analysis Steps

---++ Exercise 1 - Setup the working area

---+++ Release & Software

Log to a computing node (Currently we have node02~node15):
<pre class="command">
ssh node02
</pre>

Create working directory, set cmssw release:
<pre class="command">
cp /md3000/scratch01/sw/cmsset_default.sh ./
source cmsset_default.sh

mkdir UpsilonAna 
cd UpsilonAna
scramv1 list | grep CMSSW
cmsrel CMSSW_3_1_3

cd CMSSW_3_1_3/src
cmsenv
</pre>

Set up [[https://twiki.cern.ch/twiki/bin/view/CMS/WorkBookComputingConcepts#CvsCheckoutModules][CVS]]
<pre class="command">
export CVS_RSH=/usr/bin/ssh
export CVSROOT=:pserver:anonymous@cmscvs.cern.ch:/cvs_server/repositories/CMSSW
cvs login
</pre>
The password is the famous CMS common password: *98passwd*

If you see an error message like =Unknown host cmscvs.cern.ch= on some nodes, please change to another node. You'll need to use CVS to check out code and configuration files to your area so that you can modify and use them. ( =Notice= The frequently-used CVS package for Jpsi and Upsilon analysis is the official [[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/CMSSW/HeavyFlavorAnalysis/Onia2MuMu/][Onia2MuMu]] package. But in this tutorial, we will use a much more condensed version [[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/][PKUTutorial]] instead .)

Checkout and compile required software tags:
<pre class="command">
cvs co -d zhenhu/PKUTutorial UserCode/zhenhu/PKUTutorial

addpkg MuonAnalysis/MuonAssociators                     V01-01-00
addpkg PhysicsTools/TagAndProbe                         V01-08-01
addpkg MuonAnalysis/TagAndProbe                         V06-02-01
addpkg CondCore/PhysicsToolsPlugins                     V00-00-03-01
addpkg CondFormats/BTauObjects                          V01-03-00
addpkg CondFormats/DataRecord                           V06-07-03-01
addpkg CondFormats/PhysicsToolsObjects                  V01-02-07-01
addpkg RecoBTag/PerformanceDB                           V00-01-00
addpkg RecoBTag/Records                                 V00-01-00
addpkg RecoMuon/Records                                 V00-01-03

cd PhysicsTools/TagAndProbe
patch -p0 < ../../zhenhu/PKUTutorial/test/tnp-v010801-p5.patch

cd ../..
addpkg GeneratorInterface/Pythia6Interface           V01-04-39
cd GeneratorInterface/Pythia6Interface
patch -p0 < ../../zhenhu/PKUTutorial/test/pythia6PtGun_Rapidity.patch

cd ../../PhysicsTools/TagAndProbe
patch -p0 < ../../zhenhu/PKUTutorial/test/tripleGaussianLineShape.patch

cd ../..
scramv1 b -j4
</pre>
=this takes a few minutes=
 
Consider the test directory as the default working location
<pre class="command">
cd zhenhu/PKUTutorial/test
</pre>


---++ Exercise 2 - Calculation of Acceptance

The CMS detector does not cover the whole eta range therefore a fraction of Upsilons decaying to muons will not be detected. Also tracks from muons with low pT will not be identified as muons as the low pT muons cannot reach the muon system. Therefore there is a need to estimate what fraction of Upsilons can be detected assuming 100% detector efficiency. This fraction is called geometric and kinematic acceptance. In this analysis we accept muons in the pseudorapidity range |&#951;| < 2.1. We make this choice to match the eta range of the single muon trigger. Within this range we assume full detector coverage. We also require both muons to have pT > 3.5 !GeV to have sufficient muon identification and triggering efficiencies. The acceptance is a function of Upsilon pT, rapidity and polarization.

To estimate the acceptance of Upsilons we rely on Monte Carlo simulations. In contrast, the efficiencies of muon identification and triggering can be estimated from the data with the Tag and Probe method, described below in Exercise 3.
However, the efficiency of a muon being reconstructed with a track in the silicon tracking system needs MC simulations and therefore it is combined with the acceptance. Thus, out final definition of acceptance is the fraction
of generated Upsilons decaying to muons that are reconstructed with silicon tracks of opposite charge with pT > 3.5 !GeV and |&#951;| < 2.1 and also the invariant mass is in the mass window of the Upsilon. Formally:

%BEGINLATEX%
  \begin{displaymath}
  {\mathcal A}\left(p_T^\Upsilon,y^\Upsilon \right) = \frac{N^{\rm reco}\left( \left. p_T^\Upsilon,y^\Upsilon \right| p_T^{\rm track}>3.5{\rm GeV},|\eta^{\rm track}|<2.1 \right)} {N^{\rm gen}\left({p'}_T^\Upsilon,y'^\Upsilon \right)}
  \end{displaymath}
%ENDLATEX%

---+++ Step 1 - Generate an "Upsilon Gun" Data Sample

When generating Upsilon events with PYTHIA, the pT spectrum of Upsilons is steeply falling and the statistics of events at high pT is low. In addition, the presence of the underlying event prolongs the simulation of events significantly. Hence we use an "Upsilon gun" that produces events that contain only the Upsilon, distributed flat in pT and Rapidity, and the daughter muons with zero polarization. Then all events are full-simulated and reconstructed. The =upsilonGun_cfg.py= job configuration in the =test= directory does the above mentioned steps. %ORANGE%(For another generator examples, please see [[https://cmsweb.cern.ch/dbs_discovery/getAppConfigs?dbsInst=cms_dbs_prod_global&appPath=*&procPath=/Upsilon1S/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RAW&ajax=0&userMode=user][Upsilon1S]], and [[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/CMSSW/Configuration/Examples/python/H200ZZ4L_cfi_py_GEN_SIM_DIGI_L1_DIGI2RAW_HLT_MC.py][H200ZZ4L]].)%ENDCOLOR%

=upsilonGun_cfg.py= contains the parameters of the "Pythia6PtGun" module:
<pre class="code">
process.generator = cms.EDProducer("Pythia6PtGun",
    PGunParameters = cms.PSet(
        MinPhi = cms.double(-3.14159265359),
        MinPt = cms.double(0.0),
        ParticleID = cms.vint32(553),
        MaxRapidity = cms.double(2.0),
        MaxPhi = cms.double(3.14159265359),
        MinRapidity = cms.double(-2.0),
        AddAntiParticle = cms.bool(False),
        MaxPt = cms.double(20.0)
    ),
...
</pre>
The ID of Upsilon(1S) is 553. We are planning to measure the Upsilon cross section in the Rapidity range (-2,2) and pT range (0,20) !GeV. Adjust the kinematic phase-space of the Upsilon to somewhat larger range as due to resolution effects an Upsilon generated outside the measured range can be reconstructed within. Please ensure that the Upsilons decay only to muons by changing the branching fraction as shown below:
<pre class="code">
pythiaUpsilonDecays = cms.vstring(
    'MDME(1034,1)= 0 ! 0.025200    ! e- e+',
    'MDME(1035,1)= 1 ! 0.024800    ! mu- mu+',
    'MDME(1036,1)= 0 ! 0.026700    ! tau- tau+',
    'MDME(1037,1)= 0 ! 0.015000    ! d dbar',
    'MDME(1038,1)= 0 ! 0.045000    ! u ubar',
    'MDME(1039,1)= 0 ! 0.015000    ! s sbar',
    'MDME(1040,1)= 0 ! 0.045000    ! c cbar',
    'MDME(1041,1)= 0 ! 0.774300    ! g g g',
    'MDME(1042,1)= 0 ! 0.029000    ! gamma g'),
</pre>
The schedule clearly shows the executed steps: generation, simulation,...,reconstruction:
<pre class="code">
process.schedule = cms.Schedule(
  process.generation_step,
  process.simulation_step,
  process.digitisation_step,process.L1simulation_step,process.digi2raw_step,process.raw2digi_step,
  process.reconstruction_step)
</pre>

It would require significant space to save every object in the output file. Therefore, to save space, an analyzer has been prepared  =DimuonTree.cc= in the =../src= directory that dumps only the necessary variables into a TTree.
This basic code will also allow you to understand how to access information from a data sample root file. Fifteen parameters are saved into a TTree, including the generated momenta of Upsilons and muons along with the  momenta of reconstructed tracks.

Adjust the number of required events to 100 events:
<pre class="code">
process.maxEvents = cms.untracked.PSet(
    input = cms.untracked.int32(100)
)
</pre>
Test the configuration by running
<pre class="command">
cmsRun upsilonGun_cfg.py
</pre>
To check the output, open the resulting upsilonGun.root file: 
<pre class="command">root -l upsilonGun.root
root [1] TBrowser b
</pre>
Click on "ROOT Files", and then "upsilonGun.root" and then "UpsTree", you will find 15 branches inside. Click on each branch, to see the distribution of each parameter.
Or you can scan the contents of the tree:
<pre class="command">
root [2] UpsTree->Scan("*");
</pre>
It will display all the branches in the tree like below:

%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" <br />                showimgleft="%ICONURLPATH%" <br />                hideimgleft="%ICONURLPATH%"}% <img alt="scanout.png" src="%ATTACHURLPATH%/scanout.png" /> 
%ENDTWISTY% 

=Notice=: The generated values of the Y and muons depends on the random number generator in Pythia and so differ from the above example. However, the structure of the tree is the same.

If everything looks fine, please log on the CERN computing server (=lxplus.cern.ch=), or log on our T3 site at Peking University (=grid08.phy.pku.edu.cn=). Then you can submit a CRAB job to produce larger statistics. 

=Notice=: You have to create the same CMSSW working area before submitting CRAB jobs.

%TWISTY{mode="div" showlink="Show-CRAB-instruction" hidelink="Hide-CRAB-instruction" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%

Modify the =upsilonGun_cfg.crab= configuration to submit 100 jobs producing 500 events each. 

First initiate your proxy: 
<pre class="command">voms-proxy-init -voms cms
</pre>

Set up CRAB: 
<pre class="command">source /home/cmssoft/CRAB/CRAB_2_6_6/crab.sh
</pre>

Then execute:
<pre class="command">
crab -create -submit -cfg upsilonGun.crab
</pre>
To check the job status, run:
<pre class="command">
crab -status -c upsilonGun
</pre>

Each event takes about 2 seconds, so the jobs will run for about 20 minutes. In the meantime one could start working on Step 2. When all jobs are "Done", retrieve the output with
<pre class="command">
crab -getoutput -c upsilonGun
</pre>

%ENDTWISTY%

The CRAB results will be in the =upsilonGun/res/= directory. To merge them, use the standard ROOT tool
<pre class="command">
hadd -f upsilonGun.root upsilonGun/res/upsilonGun_*.root
</pre>

The resulting data sample is saved in upsilonGun.root (overwriting the previous version).

---+++ Step 2 - Calculate Acceptance

Since the acceptance depends on the pT and Rapidity of the Upsilon, we calculate it in bins of pT and Rapidity. The polarization dependence will be studied as a systematic uncertainty.
We are still in the directory "zhenhu/PKUTutorial/test". There is a ROOT macro named "acceptance.C". It defines a two dimensional histogram for the generated Upsilon pT and Rapidity and it is filled for each event of the upsilonGun.root sample generated in the previous exercise.
<pre class="come">
TH2F* genPtRap = new TH2F("genUps","",4,0,20,4,-2,2);
for(int i=0; i < t->GetEntries(); i++){
  genPtRap->Fill( genUpsPt[0], genUpsRapidity[0] );
  ...
}
</pre>
There is another 2D histogram, which is a copy of the above, that collects events in which the Upsilon is reconstructed with two tracks of opposite charge, pT > 3.5 !GeV, |&#951;| < 2.1 and invariant mass within 1.0 !GeV of the PDG value 9.46 !GeV.
<pre class="code">
TH2F* recoPtRap = (TH2F*)genPtRap->Clone("recoUps");
for(int i=0; i < t->GetEntries(); i++){
  if ( recoMuCharge[tr1]*recoMuCharge[tr2] == -1 && recoMuPt[tr1] >= 3.5 && recoMuPt[tr2] >= 3.5 && fabs(recoMuEta[tr1]) < 2.1 && fabs(recoMuEta[tr2]) < 2.1 ){
    ...
    if( minDeltaM < 1.0 ){
      recoPtRap->Fill( recoUpsPt, recoUpsRapidity );
    }
  }
}
</pre>
The ratio of the two histograms is the acceptance by definition.
<pre class="code">
acc->Divide(recoPtRap, genPtRap, 1, 1, "B");
</pre>
To run the macro: 
<pre class="command">
make acceptance #compiles acceptance.C
./acceptance upsilonGun.root acceptance.root
</pre>
To print out the result:
<pre class="command">
root -l acceptance.root
root [1] acceptance->Print("range")
</pre>
%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
<img width="594" alt="acceptancePrint.png" src="%ATTACHURLPATH%/acceptancePrint.png" />
%ENDTWISTY% 

To measure the acceptance with better precision a larger sample of generated events is required. To save time, we have prepared a tree with 10M events following step 1. It is located at the SE of our T3 Site (=grid09.phy.pku.edu.cn=). You can transfer it to your local directory and give it a new name =upsilonGun_new.root=:
<pre class="command">
scp PKUTutorial@grid09.phy.pku.edu.cn:/md1000_1/user/zhenhu/Tutorial/upsilonGun.root ./upsilonGun_new.root
</pre>
The passwd for the user PKUTutorial is 111111.

=Notice:= If you can not use the scp transfer, try to logout the node you are working on, and then log in hepfarm01 or hepfarm02.

Now the binning of the acceptance can be refined. Please adjust it to pT (20,0,20) and Rapidity (40,-2,2) in the =acceptance.C= and run:
<pre class="command">
make acceptance
./acceptance upsilonGun_new.root acceptance.root
</pre>
The result can be plotted with =acceptancePlot.C= that saves an =acceptance.png= figure.
<pre class="command">
root -b -q acceptancePlot.C
</pre>
%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
<img width="594" alt="acceptance.png" src="%ATTACHURLPATH%/acceptance2.png" />
%ENDTWISTY% 

=Quiz1:= Please write a piece of C++ code to plot the muon pT distribution, muon eta distribution, Upsilon pT distribution, and Upsilon eta distribution at generator level.

=Quiz2:= Please write a piece of C++ code to plot the muon pT distribution, muon eta distribution, Upsilon pT distribution, and Upsilon eta distribution at reconstruction level.

=Quiz3:= In what pT range can the Upsilon cross section be measured if we accept muons only with pT > 10 !GeV?


---++ Exercise 3 - Using Tag and Probe to measure efficiencies

*Tag and Probe methodology*

Tag and Probe (T&P) is a data driven method for efficiency calculations. It utilizes resonances to identify probe objects. Assuming no efficiency correlation between the two decay products of the resonance it identifies one of the muons, called a Tag, using tight identification criteria and measures the efficiency of the other muon, referred to as a Probe. For detailed explanation of Tag and Probe analysis of Upsilon, please read =CMS AN2009_119=.

*Efficiency components:*
   * Tracking efficiency (assuming it to be 1)
   * Tracker muon ID efficiency
   * Trigger efficiency


---+++ Step 1 - Skim the Data Samples

A MC data sample equivalent to 1.87/pb integrated luminosity (455492 events) has been produced to use in the exercise, and is located at 
=grid09.phy.pku.edu.cn:/md1000_1/user/zhenhu/Tutorial/skim_1.87pb-1.root= . Please scp transfer it to your working directory. 

Next it's explained how this was put together, starting from officially produced samples.

   * List of signal and background central monte carlo datasets on !DBS 
      * =/Upsilon1S/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RECO=
      * =/Upsilon2S/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RECO=
      * =/Upsilon3S/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RECO=
      * =/ppMuMuX/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RECO=

Take Upsilon1S for example. 

%TWISTY{mode="div" showlink="Show Examples" hidelink="Hide Examples" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%

Go to the DBS webpage, search the dataset "[[https://cmsweb.cern.ch/dbs_discovery/aSearch?caseSensitive=on&userMode=user&sortOrder=desc&sortName=&grid=0&method=dbsapi&dbsInst=cms_dbs_prod_global&userInput=%2FUpsilon1S%2FSummer09-MC_31X_V3_7TeV-v1%2FGEN-SIM-RECO][/Upsilon1S/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RECO]]". First make a note of the total number of events in this dataset: "contains 1166738 events". Then click on its [[https://cmsweb.cern.ch/dbs_discovery/getData?dbsInst=cms_dbs_prod_global&proc=/Upsilon1S/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RAW&userMode=user&ajax=0&phedex=off][parents]], then click [[https://cmsweb.cern.ch/dbs_discovery/getAppConfigs?dbsInst=cms_dbs_prod_global&appPath=*&procPath=/Upsilon1S/Summer09-MC_31X_V3_7TeV-v1/GEN-SIM-RAW&ajax=0&userMode=user][Conf.files]]. You can see the configuration file used for generating Upsilon1S to dimuon samples. Inspect the contents and notice the lines below:
<pre class="code">
    filterEfficiency = cms.untracked.double(0.139),
</pre>
The "filterEfficiency" has to do with the filter that is used in the generation (like cuts on muon Pt and Eta). It is defined as the ratio between events passing the filter and the total number of generated events by PYTHIA. For example if the filterEfficiency is 0.01, it means of every 100 events PYTHIA generates, only 1 events is of interest for us, and 99 events are thrown away.
<pre class="code">
    comEnergy = cms.double(7000.0),
</pre>
The center-of-mass energy is  7 !TeV.
<pre class="code">
    crossSection = cms.untracked.double(99900.0),
</pre>
The number in "crossSection" is a value in [pb] and is the product of two factors:
1) The production cross-section "sigma" with which the particle is produced.
2) The forced branching ratio, "BR", leading to the desired decay mode in which the particle should be looked for:
<pre class="code">
'MDME(1035,1)=1   ! 0.024800    mu- mu+',
</pre>

The integrated luminosity is the number of events before filter divided by the production cross-section. In this case, it should be (1166738/0.139)/99900 = 84.02 /pb .
Similarly, we calculated the intergrated luminosity of the other datasets. And we see the background sample "ppMuMuX" has the smallest integrated luminosity 1.87/pb. So to make things more realistic, we decide to use 1.87/pb signal samples to make the level of signal and background compatible. To do this, we just need to calcuate how many events we need for the signals. Take Upsilon 1S for example again. We already measured the integrated luminosity of Upsilon 1S dataset is 84.02/pb corresponding to 11667380 events. So for 1.87/pb, we should have 1166738*(1.87/84.02) = 25967 events. For Upsilon 2S and 3S, we just repeated this calculation.

*Skim the Data Samples*

Inspect the python configuration file: 
[[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/test/skimUpsilon_cfg.py?view=markup][skimUpsilon_cfg.py]]

Submit CRAB jobs since the dataset is not located at PKU.

Inspect the CRAB configuration file test/skimUpsilon.crab . To submit the job:
<pre class="command">
crab -create -submit -cfg skimUpsilon1S_7TeV.crab
crab -status -c skimUpsilon1S_7TeV
</pre>
When the jobs are done:
<pre class="command">
crab -getoutput -c skimUpsilon1S_7TeV
cd skimUpsilon1S_7TeV/res
</pre>

%ENDTWISTY%

Similarly, we can prepare the same skimmed samples for Upsilon 2S and 3S along with the background sample ppMuMuX. And then we can merge them together with the script =merge_cfg.py= in order to make a date-like soup. As it will take a while to produce them, we have prepared it as pointed to above.


---+++ Step 2 - Produce tag-and-probe Ntuples

<!--
This exercise step will create a skimmed data sample that contains the PAT objects which are needed for running the Tag and Probe algorithm.
It also filters on events that contain at least one Tag and Probe pair or tarckerMuon-trackerMuon pair in the mass window 8<m<12 !GeV/c<sup>2</sup>.
-->

We will use tracker muons in this analysis. 
First, we need to select the good tracker muons that satisfy the offline selection cuts (with good track quality in geometric and kinematic acceptance).

We prepared this file "<a href="http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/src/MuonSelectorUpsilon.cc?view=markup" title="MuonSelectorUpsilon.cc">MuonSelectorUpsilon.cc</a>" to select good tracker muons. 

Please move this module code:
<pre class="command">
cp ../src/MuonSelectorUpsilon.cc ../../../MuonAnalysis/TagAndProbe/plugins/
</pre>

Open the file =MuonSelectorUpsilon.cc=
<pre class="command">
vi  ../../../MuonAnalysis/TagAndProbe/plugins/MuonSelectorUpsilon.cc
</pre>
Uncomment the last three lines in the file to make it as a CMSSW Plugin now:
<pre class="code">
/*
/// Register this as a CMSSW Plugin
#include "FWCore/Framework/interface/MakerMacros.h"
DEFINE_FWK_MODULE(MuonSelectorUpsilon);
*/
</pre>

Then compile:
<pre class="command">
cd ../../..
scramv1 b
</pre>

Make sure you are still in the =/test= directory. We prepared this configuration file "<a href="http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/test/tnp_from_skim.py?view=markup">tnp_from_skim.py</a>" to produce the Tag and Probe Ntuple.

<pre class="command">
cmsRun tnp_from_skim.py
</pre>
=it will take ~40 minutes to finish. There are about 470000 events in total.= 

Two root files will be produced. (For your convenience, a backup of these two files are also stored in =grid09.phy.pku.edu.cn:/md1000_1/user/zhenhu/Tutorial/=). Each of them will contain a TTree, with invariant mass, pt, eta and passing/failing information for measuring tracker muon ID or trigger efficiency
   * =histo_output_MuFromTkUpsTkM.root= is for the tracker muon identification efficiency
   * =histo_output_HltFromUpsTkM.root= is for the trigger efficiency


For example:
<pre class="command">
root -l histo_output_MuFromTkUpsTkM.root
root [1] fitter_tree->Scan("");
</pre>

%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" <br />                showimgleft="%ICONURLPATH%" <br />                hideimgleft="%ICONURLPATH%"}% <img alt="tnptree.png" src="%ATTACHURLPATH%/tnptree.png" /> 
%ENDTWISTY% 

---+++ Step 3 - Compute the efficiences

We supposed that you are still in /test . Start fitting:
<pre class="command">
cmsRun fit_tnp_Id_cfg.py
cmsRun fit_tnp_trigger_cfg.py
</pre>
=This part will take ~15min to finish=

Once the jobs finish, there will be a root file containing fitting results produced for each tag and probe Ntuple:

<pre class="code">
process.fitMuFromTkUpsTkM = RunFit.clone(
    ReadFromFiles = [ 'histo_output_MuFromTkUpsTkM.root' ],
    FitFileName   =     'fit_result_MuFromTkUpsTkM.root'  ,
)
</pre>
<pre class="code">
process.fitHltFromJPsiTkM = RunFit.clone(
    ReadFromFiles = [ 'histo_output_HltFromUpsTkM.root' ],
    FitFileName   =     'fit_result_HltFromUpsTkM.root'  ,
    Var2BinBoundaries   = cms.untracked.vdouble( -2.1,-1.2,0.0,1.2,2.1),
)
</pre>

Each =fit_result= file contains fitting plots in each pt/eta bin along with efficiencies via Tag and Probe or MC truth.

For example:
<pre class="command">
root -l fit_result_MuFromTkUpsTkM.root
root [1] TBrowser b
</pre>

Click on the root file name:
<pre class="command">
root [2] fit_canvas_pt_1_eta_1->Draw(" ");
</pre>

You will see the mass fitting plots of "all probes", "passing probes", "failing probes" for tracker muon ID efficiency in pt (4.5, 6), eta (-1.2,0):
%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%

</del><ins><img width="794" alt="fitplot_3signal.jpg" src="%ATTACHURLPATH%/fitplot_3signal.jpg" />
</ins>
%ENDTWISTY% 

<pre class="command">
root [3] gStyle->SetPalette(1);
root [4] gStyle->SetOptStat(0);
root [5] fit_eff_pt_eta->Draw("colz");
root [6] fit_eff_pt_eta->DrawCopy("text same");
root [7] fit_canvas_pt_1_eta_1->SetLogx();
root [8] fit_eff_pt_eta->GetXaxis()->SetMoreLogLabels();
</pre>

The tracker muon ID efficiency from Tag and Probe in each eta and pt bin is displayed:

%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%

</del><ins><img width="794" alt="IdEffPtEta.png" src="%ATTACHURLPATH%/IdEffPtEta.png" />
</ins>
%ENDTWISTY% 

You can aslo examine the MC truth efficiency "truth_eff_pt_eta" by yourself. The commands are similar to the above.

%TWISTY{mode="div" showlink="Show Trigger-Bias-Study" hidelink="Hide Trigger-Bias-Study" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%

Eventually, Tag and Probe method will be performed on real data to get efficiencies. In Monte Carlos data samples, we don't  have any trigger bias in them. That is to say, we have both the events which pass trigger and the events which are not be able to pass trigger. And we are able to know whether an event passing trigger or not. However, in real data, the events will pass trigger first and then come to us. Therefore, we always have a subset of all the events. Then the question is, will the trigger efficiency measured from real data (with trigger bias) be consistent with the one measured from Monte Carlos data samples (without trigger bias)? Let's do this studies step by step as below.

1) Produce data samples with trigger bias
We don't want to waste time to make the skimmed soup again. Instead, we will change the configuration file "tnp_from_skim.py" to force Tag and Probe only performed on those events which pass trigger.

Add the following lines in the "tnp_from_skim.py" just after the definition of "PASS_HLT":
<pre class="code">
process.triggerMuons = cms.EDFilter("PATMuonRefSelector",
    src = cms.InputTag("patMuons"),
    cut = cms.string( PASS_HLT ),
    filter = cms.bool(True),
)
</pre>
This filter simply filters events by checking whether the event contains at least one pat muon which can pass the "HLT_Mu3" trigger path. If the size of the so-called "triggerMuons" is not zero, then this event must pass the "HLT_Mu3" trigger. Otherwise, it must not. Only the events passing "HLT_Mu3" will be keeped after this filter.
Don't forget to add this process beyond all of the other processes.

2) Repeat Exercise 3 with the new "tnp_from_skim.py". Notice, when fitting the histograms, you only need to run the "fit_tnp_trigger_cfg.py" because only the trigger efficiencies may be affected due to the trigger bias. Also, please save the output files into different names. You can add "_bias" as an extension of each file name.

=QUIZ:= Are these differences between the tag and probe efficiencies measured from non-bias samples and bias samples?

If the answer to the above quiz is "yes", please continue doing the next step.

3) Open the "tnp_from_skim.py" again and check the tagMuons requirements:

<pre class="code">
process.tagMuons = cms.EDFilter("PATMuonRefSelector",
    src = cms.InputTag("patMuons"),
    cut = cms.string("isGlobalMuon && pt > 3 && abs(eta) < 2.4 "), 
    filter = cms.bool(True),
)
</pre>

=QUIZ:= Modify the above lines to require tag muons passing trigger.

Once you've done the quiz, repeat 2) with the new "tnp_from_skim.py". Save output files into new names.

=QUIZ:= Compare the efficiencies measured from 3) to the previous two tset of trigger efficienies. What will you conclude?

%ENDTWISTY% 


---++ Exercise 4 - Upsilon Selection and Yield Tree

The purpose of this exercise is to create a ROOT TTree with the Upsilon candidate information to be used for fitting the signal yield.
The input is the skimmed data sample that contains the PAT objects, produced in the previous exercise. 
The output TTree has to contain the mass, pt and rapidity of the Upsilon candidates, as well as the pt and eta of the daughter muons for efficiency corrections. 
Technically this task consist of two parts: A CMSSW python configuration [[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/test/upsilonYield_cfg.py?view=markup][upsilonYield_cfg.py]] file that defines the selection of Upsilon candidates. And there a C++ module [[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/src/YieldTree.cc?view=markup][YieldTree.cc]] that dumps the variables of the candidates to a TTree.

---+++ Step 1 - Produce the data tree from the skim

Change the Event number to -1 and run the prepared configuration:
<pre class="command">
  cmsRun upsilonYield_cfg.py
</pre>

Inspect the output root file:
<pre class="command">
root -l upsilonYield.root
root [1] upsilonYield->cd()
root [2] upsilonYield->Scan()
</pre>

%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
     <img width='500' src="%ATTACHURLPATH%/upsilonYield.png" alt="upsilonYield.png" />
%ENDTWISTY%

---+++ Step 2 - Apply selection
*QUIZ:* Modify test/upsilonYield_cfg.py to select muons with additional quality cuts:
   * number of valid silicon hits > 10
   * normalized chi2 of silicon fit < 5
   * TMOneStationTight tracker muon selection
*Hint:* =upsilonYield_cfg.py= should contain the following:
<pre class="command">
process.goodMuonsOld = cms.EDFilter("PATMuonRefSelector",
    src = cms.InputTag("patMuons"),
    cut = cms.string("track.isNonnull && pt > 3.5 && abs(eta) < 2.1"),
)
process.goodMuons = cms.EDProducer("MuonSelectorUpsilon",
    src = cms.InputTag("goodMuonsOld"),
    selectGlobalMuons = cms.bool(False)
)
</pre>
Rerun the job to obtain the new tree.


---++ Exercise 5 - Cross Section

We have now the various ingredients in place for estimating the cross section.

%BEGINLATEX%
  \begin{displaymath}
\sigma_{\rm{tot}} \times Br(\Upsilon \to \mu\mu) =  \frac{N_{\rm{fit}}^{\rm corr.}}{L}
  \end{displaymath}
%ENDLATEX%

%BEGINLATEX%
  \begin{displaymath}
\frac{d\sigma}{dp_T} \times Br(\Upsilon \to \mu\mu) = \frac{N_{\rm{fit}}^{\rm corr.}(p_T)}{L \cdot \Delta p_T}
  \end{displaymath}
%ENDLATEX%

   * *L* denotes the luminosity of the sample.
   * *&#916;p<sub>T</sub>* is the width of the dimuon pT bin
   * *N* is the corrected yield 

The corrected yield is extracted from the fit to the dimuon invariant mass distribution. In the fit, each event carries as weight which corresponds to the inverse of the product of the &#933;-acceptance and &#956;-efficiencies. The latter corrections are determined from the acceptance and efficiency maps determined previously.

---+++ Step 1 - Acceptance and efficiency corrections

In the first step, the event weights are computed, and appended to the data yield tree.  
The ROOT macro [[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/test/makeWeights.C?view=markup][makeWeights.C]] will take the yield file, =upsilonYield.root= , as well as the efficiency and acceptance files as input and produce an output file =upsilonYieldWeighted.root= that contains the same upsilonYield tree but with the weight column included in addition. 
Please verify these files are available in the current working directory, or otherwise gather them there.
<pre class="command">
upsilonYield.root
acceptance.root
fit_result_MuFromTkUpsTkM.root
fit_result_HltFromUpsTm.root
</pre>

To run it execute:
<pre class="command">root -b -q 'makeWeights.C("upsilonYield.root", "acceptance.root", "fit_result_MuFromTkUpsTkM.root", "fit_result_HltFromUpsTm.root", "upsilonYieldWeighted.root")'</pre>

%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
    <img src="%ATTACHURLPATH%/upsilonYieldWeighted.png" alt="upsilonYieldWeighted.png" width='400' />
%ENDTWISTY%


---+++ Step 2 - Fit the upsilon mass spectra

The baseline code for the cross section fitting part of the exercise is implemented in [[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/zhenhu/PKUTutorial/test/oniafitter.C?view=markup][oniafitter.C]]. 
The various steps are implemented as separate functions therein, eg =buildPdf, readData, fitYield= . 

Fitting is performed with the standard minuit/root/roofit tools. The program may be executed as follows.
<pre class="output">
root -l -b -q oniafitter.C >& log &</pre>
or
<pre class="output">root -l 
root [0]  .L oniafitter.C+
root [0]  oniafitter()
</pre>
You'll need to edit the code to select the various steps you like to be run.


The model description for the signal and background mass distributions need to be specified. A simple model is provided, which assigns a second order polynomial pdf for the background, while the signal peaks are each described by a double gaussian (along with tail polynomial to account for final state radiation). 

*Quiz:* Inspect the provided pdf implementations
%TWISTY{mode="div" showlink="show" hidelink="hide" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
<pre class="code">
 RooAbsPdf  *pdf  = new RooAddPdf("pdf","total signal+background pdf", 
				   RooArgList(*sigPdf,*bkgPdf),RooArgList(*nsig,*nbkg));
</pre>
Start with the =buildPdf= method, and especially verify the signal and background functions.
%ENDTWISTY%

*Quiz:* Run the <i>raw</i> fit, with no weights, over the full sample.
%TWISTY{mode="div" showlink="solution" hidelink="hide" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
un-comment code:
<pre class="code">
  /// fit raw yield
  fitYield(*ws,"total");
  plotMass(figs_ + "/mass_raw.gif",*ws);
</pre>
%ENDTWISTY%
%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
    <img src="%ATTACHURLPATH%/mass_raw.gif"  width='400' />
%ENDTWISTY%

%GRAY%Suggested exercise:%ENDCOLOR% 
Inspect/quantify the goodness of the fit, and make adaptions to the model to possibly improve the description of the data.

---+++ Step 3 - Extract the corrected yield

The efficiency and acceptance corrections are embedded in the event weights, which were computed and added to the input root three previously.  The corrected yield is extracted by repeating the fit to the weighted dataset. 

*Quiz:* Run the <i>weighted </i> fit over the full sample.

%TWISTY{mode="div" showlink="solution" hidelink="hide" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
un-comment code:  
<pre class="code">
 /// fit corrected yield 
  ((RooDataSet*)ws->data("data"))->setWeightVar(*ws->var("weight"));
  fitYield(*ws,"total");
  plotMass(figs_ + "/mass_wei.gif",*ws);
</pre>
%ENDTWISTY%
%TWISTY{mode="div" showlink="Show result..." hidelink="Hide result..." remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
    <img src="%ATTACHURLPATH%/mass_wei.gif"  width='400' />
%ENDTWISTY%

*Quiz:* Compute the average weight. Compare the obtained weighted and raw yields as a cross-check.

---+++ Step 4 - Extract the cross section

---++++ !!Total, &#963;

All left to do is to retrieve the measured yields from the saved fit results, and normalize by the sample's luminosity (1.87 pb<sup>-1</sup>). 

*Quiz:* Compute the total cross section.
%TWISTY{mode="div" showlink="solution" hidelink="hide" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
un-comment code:  
<pre class="code">
 /// total cross section
  xsectTot(*ws);
</pre>
%ENDTWISTY%


---++++ !!Differential, d&#963;/dp<sub>T</sub>

For extracting the differential cross section, the dataset is divided in bins of dimuon transverse momentum (this quantity is part of the input root tree), and the fitting procedure used above is applied to the individual pT-bin sub-samples.

*Quiz:* Compute the differential total cross section.
%TWISTY{mode="div" showlink="solution" hidelink="hide" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
un-comment code: 
<pre class="code">
 /// cross section vs pT
  xsectDif(*ws,true);
</pre>
note: set argument to false if fits do not need to be repeated
%ENDTWISTY%


*Quiz:* Compute the total and differential cross section for the individual 1S, 2S, 3S resonances.
%TWISTY{mode="div" showlink="hint" hidelink="hide" remember="on" 
                showimgleft="%ICONURLPATH{toggleopen-small}%" 
                hideimgleft="%ICONURLPATH{toggleclose-small}%"}%
Extract the yields from the individual peaks, and repeat the procedure above. 
%ENDTWISTY%

---+ Your comments and feedback



-- Main.ZhenHu - 13-Jan-2010
Attachments
Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	IdEffPtEta.png	r1	manage	52.3 K	2010-01-14 - 12:56	ZhenHu
png	acceptance.png	r1	manage	7.3 K	2010-01-14 - 12:55	ZhenHu
png	acceptance2.png	r1	manage	10.2 K	2010-01-14 - 12:41	ZhenHu
png	acceptancePrint.png	r1	manage	21.3 K	2010-01-14 - 12:55	ZhenHu
png	fitplot.png	r1	manage	64.7 K	2010-01-14 - 12:56	ZhenHu
jpg	fitplot_3signal.jpg	r1	manage	72.9 K	2010-01-14 - 12:56	ZhenHu
gif	mass_raw.gif	r1	manage	9.0 K	2010-01-14 - 12:57	ZhenHu
gif	mass_wei.gif	r1	manage	9.7 K	2010-01-14 - 12:57	ZhenHu
png	scan.png	r1	manage	79.0 K	2010-01-14 - 12:58	ZhenHu
png	scanout.png	r1	manage	79.0 K	2010-01-14 - 13:00	ZhenHu
png	tnptree.png	r1	manage	26.1 K	2010-01-14 - 13:01	ZhenHu
png	triggerEffPt.png	r1	manage	40.0 K	2010-01-14 - 13:01	ZhenHu
png	upsilonYield.png	r1	manage	74.8 K	2010-01-14 - 13:02	ZhenHu
png	upsilonYieldWeighted.png	r1	manage	37.5 K	2010-01-14 - 13:03	ZhenHu
png	upsilonpt.png	r1	manage	13.5 K	2010-01-14 - 13:02	ZhenHu
Topic revision: r20 - 2011-03-29 - unknown
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