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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 Jas4pp program (assumes “bash”):

wget -O jas4pp.tgz
tar -zvxf jas4pp.tgz
cd jas4pp
source ./ # takes 5 sec for first-time optimization

Description is available from

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.

cd examples/slic/
hs-get gev250ee_pythia6_zpole_ee%rfull002 gev250ee_pythia6_zpole_ee # download all files

Z-peak from PFA

you can also do do some simple fit:


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.


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

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 gev250ee_pythia6_higgs_gamgam: We set pT(γ)>10 GeV.

hs-get gev250ee_pythia6_higgs_gamgam%rfull002 gev250ee_pythia6_higgs_gamgam 

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 gev250ee_pythia6_zpole_bbar. We assume pT(jet)>20 GeV.

hs-get gev250ee_pythia6_zpole_bbar%rfull002 gev250ee_pythia6_zpole_bbar

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 gev250ee_pythia6_higgs_zz_4l.

hs-get gev250ee_pythia6_higgs_zz_4l%rfull002 gev250ee_pythia6_higgs_zz_4l  # download 100 files in 2 threads

Higgs from 4L

Higgs from bbar

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

hs-get gev250ee_pythia6_higgs_bbar%rfull002 gev250ee_pythia6_higgs_bbar  

Jet energy resolutions

This example shows the jet energy resolution in 2 pT(truth) regions. It is based on inclusive jet sample 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.

hs-get gev250ee_pythia6_qcd_all%rfull002 gev250ee_pythia6_qcd_all

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:

jaspp sifcch1.heprep

You can download the heprep file from; 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:

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, therefore, you do not need manual download of heprep files.

Sergei Chekanov 2015/10/08 09:31

fcs/cepc/intro.txt · Last modified: 2016/04/08 16:54 by asc