Rapidity Boost Tool

The rapidity boost tool is designed for the pPb after burner boost. The standard generator would give the output in the COM frame, so we need to add a boost to get the final output in the lab frame.

How to get the plugin

cvs co GeneratorInterface/HiGenCommon
scram b

The plugins/BetaBoostEvtVtxGenerator.cc is the plugin used for boost. This plugin is based on the BetafuncEvtVtxGenerator.cc. The boost matrix is modified and parameter Beta is introduced for the boost value.

Some results for the pPb simulation boost

The pPb simulation is run under CMSSW_5_0_1_patch3. We used only "momentum" boost in the code. The cfg file including the boost can be found at:

/net/hisrv0001/home/lingshan/CMSSW_5_0_1_patch3/src/GeneratorInterface/PPbSim/pPbboost.py

The following 2 plots demonstrates the rapidity distribution before and after shift.

Upgrade of package(Sep. 06 2012)

The new release is GeneratorInterface/HiGenCommon V00-01-02

The difference of new code and old code are(CVS):

* 262,269 ****
         tmpboostZ(3,2)=0.;
         tmpboostZ(3,3) = 1.;
  
!        tmpboostXYZ=tmpboost*tmpboostZ;
!        tmpboost.Invert();
  
  
  
--- 262,269 ----
         tmpboostZ(3,2)=0.;
         tmpboostZ(3,3) = 1.;
  
!        tmpboostXYZ=tmpboostZ*tmpboost;
!        tmpboostXYZ.Invert();

Which fix the bug of the matrix. The code now does the inversion of the matrix. So the output matrix would do the rapidity boost from COM frame to lab frame first, and then the boost from heads-on direction to the real direction.

The boost tool in the package:

https://github.com/CmsHI/cmssw/blob/CMSSW_7_0_X/GeneratorInterface/HiGenCommon/plugins/BetaBoostEvtVtxGenerator.cc

The parameter sets in contained here:

https://github.com/CmsHI/cmssw/blob/CMSSW_7_0_X/GeneratorInterface/HiGenCommon/python/VtxSmearedRealisticPPbBoost8TeVCollision_cff.py

(The parameter sets we proposed to add into the official parameter set is:

http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/lixu/PPbBoost/python/Frag_vtxParameters_boost.py?revision=1.2&view=markup

The cfi file we proposed to add is:

http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/lixu/PPbBoost/python/VtxSmearedRealisticPPbBoost8TeVCollision_cfi.py?revision=1.1&view=markup

The plot comparing the updated code and previous code is below. The result shows the boost matrix should be same as before with the bug fixed.)//link not working