General information

Jet Core cluster splitting + Jet Core tracking are NOW testing in 76X,


-You can check out the CMSSW version with branch clustersplitting_03 at

-You can check the report to HI Tracking meeting here,



The jet core cluster splitting is borrowed from the pp people of CMS, and the purpose of "cluster splitting" is to resolve the problem of merging clusters from very high pT jets (high pT tracks). The "cluster splitting" somehow (some algorithem develped from pp people) can split some merged clusters (split one cluster into 2 subclusters), and increase the track efficiency at those high pT regime.

The algo can be found here in the slides that was given by TRKPOG meeting. TRKPOG-splitting.pdf

The Jet core regional tracking is one step usually come after the jet core cluster splitting, which is an additional iteration of tracking after the general standard tracking in HI.

Basially, this can be seen as the following step:

1. Jet finding, with hiInitialJetCoreClusterSplitting added before hiBasicTracking. Besides adding the part with jets finding, part of the names of the collection have been change to "XXXPreSplitting", because after cluster splitting, we want to keep the same name as before (i.e "siPixelClusters" ) and then all the following steps would not be changed. You can find detail in

2. Pixel cluster splitting. The module name is "siPixelClusters" that can be found in the tracking step.

3. Standard HI tracking (this part has not been changed)

4. Adding Jet Core regional tracking at the end of HI tracking as hiJetCoreRegionalStep.

5. Merge all tracks from all steps (Jet Core added)


- BG subtracted jets vs w/o subtracted jets

- with jet core cluster splitting but WITHOUT jet core regional tracking to see what effects would be reflected in each step in terms of efficiency, fake rates

- Centrality dependences

- Try Cut-based selection on the tracks and later MVA selections

- The lastest IB version cannot run crab job, to do more events, jump down to the lower versions that support CRAB.

github tips

For work that needs to be modifying cmssw code

First, it is very important to start with a clean setup. Always try something new with the clean setup so that it is easier to keep track and would not mess up with the existing working files.

Then, before doing anything on lxplus, we need to first fork the cmssw repo and create a brand new branch, the following steps are about creating a new branch and commit to the new branch

after that, (for example in 75X)

scram p CMSSW CMSSW_7_5_X_2015-07-15-2300

cd CMSSW_7_5_X_2015-07-15-2300/src

export SCRAM_ARCH=slc6_amd64_gcc491

eval `scram ru -sh`

git cms-init

git checkout CMSSW_7_5_X

Now try to create your own branch:

git checkout -b YourOwnBranchDemo

you can check that by doing "git branch" to see what branch you are on.

NOW, check out the packages that has been modified ONLY! For example,

git cms-addpkg RecoHI /HiTracking

git cms-addpkg Configuration/StandardSequences

git cms-addpkg RecoLocalTracker /Configuration

Now, try to copy the modifed files from the other working area (that you have been working under) to this new checkout directory. Then you can do "git status" to see which files are added (not in the pacakge before) and which files were modifed

for those added files, you need to do git add ../../filename

When this is ready to go,

git commit -a -m "changes"

git push [remote name] YourOwnBranchDemo

Then you suppose to see your branch in your forked cmssw area. Click on Compare to see the differences.

-- ZhoudunmingTu - 2015-07-22

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PDFpdf TRKPOG-splitting.pdf r1 manage 1131.9 K 2015-07-22 - 16:46 ZhoudunmingTu  
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