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===== CEPC detector studies =====
**People:** S.Chekanov, M.Demarteau

This wiki explains how to view electron-proton collision events for CEPC. 
To analyse events for such studies, install [[http://atlaswww.hep.anl.gov/asc/jas4pp/|Jas4pp]] program (assumes "bash"):

<code bash>
wget http://atlaswww.hep.anl.gov/asc/jas4pp/download/current.php -O jas4pp.tgz
tar -zvxf jas4pp.tgz
cd jas4pp
source ./setup.sh # takes 5 sec for first-time optimization
</code>

Description is available from [[https://wiki.inside.anl.gov/inside/HEP/CEPC]].



===== Z-peak using PFA =====
Let's calculate Z peak from particle-flow objects after full reconstruction using Pandora.
You do not run "hs-get" command if you have done this before.

<code bash>
cd examples/slic/
hs-get gev250ee_pythia6_zpole_ee%rfull002 gev250ee_pythia6_zpole_ee # download all files
fpad mc_pflow.py
</code>


{{:fcs:mc_pflow_sidcc1.png?400|Z-peak from PFA}}

you can also do do some simple fit:

<code bash>
fpad mc_pflow_fit.py
</code>

{{:fcs:mc_pflow_fit_sidcc1.png?400|}}

===== Z-peak using tracks =====

Let's calculate Z peak from reconstructed tracks (no Pandora and no particle identification)
You do not run "hs-get" command if you have done this before.

<code bash>
fpad mc_tracks.py
</code>

Please correct on line 47 the variable Bfield=5 to Bfield=4 Tesla!

{{:fcs:mc_tracks_sidcc1.png?400|Z-peak from tracks}}

===== Higgs from γ γ=====

Let's calculate the Higgs peak from reconstructed photons after the PFA algorithm. This time
you will need H-> gamma+gamma sample [[http://atlaswww.hep.anl.gov/hepsim/info.php?item=152|gev250ee_pythia6_higgs_gamgam]]:
We set pT(γ)>10 GeV.

<code bash>
hs-get gev250ee_pythia6_higgs_gamgam%rfull002 gev250ee_pythia6_higgs_gamgam 
fpad mc_gammagamma.py
</code>

{{:fcs:mc_gammagamma_sidcc1.png?400|Higgs from gamma+gamma}}

===== Z-peak using b-jets =====
Let's calculate Z peak from reconstructed b-jets. Jets are reconstructed using the Durham kT algorithm with ycut=0.05.
This time we will download Z-> bbar sample. Look at [[http://atlaswww.hep.anl.gov/hepsim/info.php?item=149|gev250ee_pythia6_zpole_bbar]]. We assume pT(jet)>20 GeV. 

<code bash>
hs-get gev250ee_pythia6_zpole_bbar%rfull002 gev250ee_pythia6_zpole_bbar
fpad mc_jets.py
</code>

{{:fcs:mc_jets_sidcc1.png?400|Z-peak from 2 jets}}

No any optimization for jet reconstruction was used. Consider other approaches to make more realistic dijet  mass.



===== Higgs from 4 leptons=====
Let's calculate Higgs peak from reconstructed leptons in the channel H(125)-> ZZ* -> 4L (electrons and muons).
We will use particle flow objects to reconstruct and identify electrons and muons.
This time we will download Higgs-> 4 lepton  sample. Look at [[http://atlaswww.hep.anl.gov/hepsim/info.php?item=150|gev250ee_pythia6_higgs_zz_4l]].

<code bash>
hs-get gev250ee_pythia6_higgs_zz_4l%rfull002 gev250ee_pythia6_higgs_zz_4l  # download 100 files in 2 threads
fpad mc_higgs_zz.py
</code>

{{:fcs:mc_higgs_zz_sidcc1.png?400|Higgs from 4L}}


===== Higgs from bbar=====

This example uses the Jade algorithm to force 2 jets, and uses H-> bbar sample:

<code bash>
hs-get gev250ee_pythia6_higgs_bbar%rfull002 gev250ee_pythia6_higgs_bbar  
fpad mc_higgs_bbar.py
</code>

{{:fcs:mc_higgs_bbar_sidcc1.png?400|}}



===== Jet energy resolutions=====

This example shows the jet energy resolution in 2 pT(truth) regions. It is based on inclusive jet sample
[[http://atlaswww.hep.anl.gov/hepsim/info.php?item=134|gev250ee_pythia6_qcd_all]]. We use Durham jets with pT(truth)>20 GeV.
Jet are constructed from PFA objects. Truth jet and reco jets are matched using dR<0.05 in phi and rapidity.


<code bash>
hs-get gev250ee_pythia6_qcd_all%rfull002 gev250ee_pythia6_qcd_all
fpad mc_jets_resol.py
</code>

{{:fcs:mc_jets_resol_sidcc1.png|Jet resolution}}

====== Wired Visualization ======

You can run Jas+Wired to visualize the simulated events.  The Wired program is included in the Jas4pp program. Run it as:
<code bash>
jaspp sifcch1.heprep
</code>
You can download the heprep file from [[http://atlaswww.hep.anl.gov/hepsim/soft/detectors/sifcch1/sifcch1.heprep]];
Alternatively, visualize the detector as **[File]-[Open data source]-[HepRep]** XML.
You will see the detector layout.

Now, we will visualize a single event: Open any *.slcio file you copied from HepSim as 
**[File]-[Open data source]-[LCIO]** file.  Then click a small button [Go] (top menu bar). It will process
 events.  Then select again **[File]-[New]-[Wired 4 view]**.  You will get an image in the Wired4 display as this:

{{:fcs:event.png?400|}}

Now press [Go] again to look at next event.

If you want to see how data records are organized inside the slcio file,
do this **[File]-[New]-[LCSim Event browser]**

To view "slcio" files, Jas4pp automatically downloads the detector  geometry from [[http://atlaswww.hep.anl.gov/hepsim/detectors.php]], therefore, you do not need manual download of heprep files.



 --- //[[chekanov@anl.gov |Sergei Chekanov]] 2015/10/08 09:31//