====== Inclusive direct photon measurements using 2011 data ======
R.Blair, S.Chekanov, R.Norberg, M.Stockton, plus the **Direct Photon** group

Public results  [[http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2013-022/ | ATLAS-CONF-2013-02]]


Current CDS note:  http://cdsweb.cern.ch/record/1453853


====== ATLAS note using 4.9 fb-1 ======



The current note is located here: [[https://svnweb.cern.ch/trac/atlasphys/browser/Physics/StandardModel/PromptPhotons/Notes/InclusivePhotons3fb]]
How to get and work with it:

Outside CERN: 

<code>
/usr/kerberos/bin/kinit   <username>@CERN.CH
</code>

(or just kinit   <username>@CERN.CH).
Then find the note:

<code>
export SVNROOT="svn+ssh://svn.cern.ch/reps/atlasphys/Physics/StandardModel/PromptPhotons/Notes/InclusivePhotons3fb"
</code>

Getting the note: 

<code>
svn co $SVNROOT
</code>

This will create a directory "InclusivePhotons3fb". "cd" into it and compile the package "make". Always make sure that you keep the most recent directory "svn update".

Modify a file, then do "svn ci" and put notes. To remove a file, use "svn remove file". To add file, use "svn add file".

Read here howto use SVN: [[https://twiki.cern.ch/twiki/bin/viewauth/Atlas/SoftwareDevelopmentWorkBookSVN]]





Old instruction:
<code>
The current note is located here: 
[[https://svnweb.cern.ch/trac/atlasusr/browser/chekanov/Physics/Photons/Notes/InclusivePhotons2011]]
How to get and work with it:
Outside CERN: 
/usr/kerberos/bin/kinit   <username>@CERN.CH
export SVNUSR="svn+ssh://svn.cern.ch/reps/atlasusr/chekanov"
Getting the note: 
svn co $SVNUSR/Physics//Photons/Notes/InclusivePhotons2011
This will create a directory "InclusivePhotons2011". 
"cd" into it and compile the package "make". Always make sure that you keep the most recent directory "svn update".
Modify a file, then do "svn ci" and put notes. To remove a file, use "svn remove file". To add file, use "svn add file".
Read here howto use SVN: [[https://twiki.cern.ch/twiki/bin/viewauth/Atlas/SoftwareDevelopmentWorkBookSVN]]
</code>







====== Status of the final results ======

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/final_gamma_pt.eps.png | final_gamma_pt.eps.png]] - pT  of gamma in |Eta(gamma)|<1.37
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/final_gamma_eta.eps.png | final_gamma_eta.eps.png]] - Eta  of gamma in the central Eta region
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/final_gamma_pt_F.eps.png | final_gamma_pt_F.eps.png]] - pT  of gamma in the forward 1.52<|Eta|<2.37

Systematical and statistical errors added in guadrature. 

Green bads shows the renormalisation scale uncertanty plus PDF uncertainties from 52 eigenvectors of CT10 PDF.
Yellow-gray band shows the renormalisation uncertanty only.

Here is a plot with 2010 cross sections (extended to 25 GeV)

  *  [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/final_gamma_pt_PUB.eps.png | final_gamma_pt_PUB.eps.png]] - pT  of gamma in |Eta(gamma)|<1.37.

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/final_gamma_pt_PUB_zoom.eps.png | final_gamma_pt_PUB_zoom.eps.png]] - same after zooming in

====== Selection cuts, data and Monte Carlo models ======


We follow the general recommendations described  [[https://twiki.cern.ch/twiki/bin/view/AtlasProtected/SMDirectPhoton2011Common| here]]

Current selection cuts:

**2011 data:**

iLumiCalc.exe --lumitag=OflLumi-7TeV-002 --livetrigger=L1_EM14 --trigger=None --xml=/tmp/lumifiles/795b77/data11_7TeV.periodAllYear_DetStatus-v18-pro08-05_CoolRunQuery-00-03-98_GammaJet.xml


  - Total Luminosity: 1.072 fb-1
  - NTUPLE_PHOTON sample
  - Event selection: 1 PV having at least 3 tracks and EF_g80_loose trigger. See: https://twiki.cern.ch/twiki/bin/view/AtlasProtected/CaloIsolationCorrections

**Photon selection:**
  - ph_goodOQ rejection
  - isEM & 0x800000 – AR cut (missing B-layer)
  - if ( !( (ph_OQ&34214)==0) ) 
  - if ( ( (ph_OQ&134217728)!=0 && (ph_reta>0.98||ph_rphi>1.0||(ph_OQ&67108864)!=0))) 
  - pT(γ)>100 GeV and |η (γ)|<1.37  and  1.52<|η (γ)|<2.37
  - Isolation cut at 7 GeV.  We use Etcone40_corrected that has both the leakage and ambient energy density pileup corrections applied. 
  - Pile-up reweighting using the standard  PileupReweighting tool


**PYTHIA  simulation**
  - Signal gamma+jet: 108082 (70 GeV),   108083 (140 GeV), 108084 (280 GeV), 119079 (500 GeV)
  - QCD  (JF sample): 105814 (70 GeV),    105815 (140 GeV),  105812 (240 GeV)
**HERWIG  simulation** (only for systematics on efficiency)
  - Signal gamma+jet: 108092 (70 GeV),   108093 (140 GeV), 108094 (280 GeV), 119078 (500 GeV)

All samples are weighted according to their cross sections and generated efficiencies

General MC status is given [[https://twiki.cern.ch/twiki/bin/view/AtlasProtected/EgammaMC11Nom#Photon_Jet_Pythia_samples| here]]


===== Pile up =============

MC simulations include pile-up as shown in this figure:
[[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_nPV.eps.png | det_nPV.eps.png]] 


====== Isolation plots ======

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_iso.eps.png | det_gamma_iso.eps.png]] - isolation for pT>100 GeV

Isolation in bins of pT

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_iso_pt1.eps.png| det_gamma_iso_pt1.eps.png]] pT>100 GeV
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_iso_pt2.eps.png| det_gamma_iso_pt2.eps.png]] 300<pT<350 GeV
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_iso_pt3.eps.png| det_gamma_iso_pt3.eps.png]] 600<pT<700 GeV

Isolations for signal and background

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_iso_DP.eps.png |  det_gamma_iso_DP.eps.png]] - for signal
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_iso_JF.eps.png |  det_gamma_iso_JF.eps.png]] - for background

====== Detector-level distributions ======


Detector level pT in the region A and D

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_pt_A.eps.png | det_gamma_pt_A.eps.png]] - pT  of gamma in region A
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_eta_A.eps.png | det_gamma_eta_A.eps.png]] - Eta  of gamma in region A

Look also at the background region:

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_pt_D.eps.png | det_gamma_pt_D.eps.png]] - pT  of gamma in region D
  
Detector level pT after the side-band backgroud subtraction. We use a simple backgrown subtraction (non-correlated) due to small statistics for MC. We use correlated quadrant method as systematics.

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_pt_corr.eps.png | det_gamma_pt_corr.eps.png]] - pT  after the subtraction using "Correlation" method
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_pt_simple.eps.png| det_gamma_pt_simple.eps.png]] - pT  after the subtraction using side-bands without correlations
  *  [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_pt_bob.eps.png| det_gamma_pt_bob.eps.png]] - pT  after the subtraction using side-bands using Bob's method
  

====== Systematical uncertainties so far ======

  - Isolation cut is changed by  - 1 GeV
  - Isolation cut is changed by  + 1 GeV
  - Photon energy scale is propogated for converted and non-converted photons (separately). *Down variation*
  - Photon energy scale is propogated for converted and non-converted photons (separately). *UP   variation*
  - HERWIG for efficiency correction - next
  - Using a simple data-driven approach without assumptions on correlations between A,B,C,D regions
  - Using alternative pile-up reweighting based on comparing nPV with the data

The tables below show the  contributions of each systematic variation in % to the total cross section: 

  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/sys_gammaPT.txt | sys_gammaPT.txt]] - for pT in the central
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/sys_gammaETA.txt | sys_gammaETA.txt]] - for pT in the forward
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/sys_gammaETA.txt | sys_gammaETA.txt]] - Eta in the central
  
The total systematic uncertainty is calculated by addeding all uncertainties in quadrature.
====== Bin-by-bin corrections for the central cuts and for systematical uncertainties ======

Bin-by-bin correction factors are defined as C= N(true photons after isolation)/N(reconstructed in the region A).
The efficiency is 1/C. 


  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/corr_pt.eps.png| corr_pt.eps.png]] - C for pT  of gamma in the central Eta region
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/corr_eta.eps.png  | corr_eta.eps.png]] - C for Eta  of gamma in the central Eta region
  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/corr_pt_F.eps.png| corr_pt_F.eps.png]] - C for pT  of gamma in the forward Eta region

====== Purity calculations ======

Purity is defined as N(after bkg subtraction)/N(region A).


  * [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/purity_gamma_pt_simple.eps.png | purity_gamma_pt_simple.eps.png]] - Purity as a function of pT


====== Gamma plus jet measurements ======

This measurement is based on the inclusive analysis above by adding a antiKT4 jet.
  
* [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/det_gamma_jet_mass.eps.png | det_gamma_jet_mass.eps.png]] - M(gamma+jet) using the quadrand A for photons

====== JETPHOX predictions ======

The JETPHOX predictions are based on the JETPHOX V1.3 (ROOT-based) generating ROOT ntuples using the pT ranges as for the final plots.
This technique is descibed on  [[https://twiki.cern.ch/twiki/bin/view/AtlasProtected/SMDirectPhotonsPhotonJetCS| the CERN Twiki]]

4 different JETPHOX ntuples were generated.
First sample has 44 PDF sets, 2 other are used to estimate PDF and scale variations, changing one scale at the time. Additional sample was generated by changing the scale and PDF scales coherently. 


PDF uncertainties  are calculated by taking a max deviation from the central value.

Scale uncertanties were estimated by considering the largest deviation from the central value using different combinations of the scale and PDF uncertainties.
 
Here are the cuts:

  * Isolation cut is 7 GeV. The cone size is 0.4
  * PT(gamma) (varies). Max PT(gamma)=2 TeV
  * PT(jet)=50 GeV    Max PT(jet)=2 TeV



====== ROOT files and figures ======

All figure are here: [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/figs/ | All figures]]

Root files and tables are available  here:
 [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/root/ | All root files]]

Jetphox prediction: [[https://atlaswww.hep.anl.gov/asc/current/DirectPhotons2011/root/jetphox.root  | here]]



===== Twiki links =====


Direct-photon group: https://twiki.cern.ch/twiki/bin/view/AtlasProtected/SMDirectPhotons

Our wiki: https://twiki.cern.ch/twiki/bin/view/AtlasProtected/PhotonJetAtANL

JetPhox wiki: https://twiki.cern.ch/twiki/bin/view/AtlasProtected/SMDirectPhotonsPhotonJetCS

Theory papers: https://twiki.cern.ch/twiki/bin/view/AtlasProtected/SMDirectPhotonsBiblio


----

 --- //[[chakanau@hep.anl.gov|Sergei Chekanov]] 2011/09/02 22:07//