Hadronic Decays of Boosted W Bosons

Introduction

We search for the hadronic decays of W bosons with a substantial Lorentz boost, such as would be produced by the decays of heavy particles. The only standard-model source of boosted W bosons is the decay of t quarks; if new heavy particles decay via the charged weak interaction, there will be a detectable surplus of boosted W bosons. These can be identified using geometrical quantities in the di-jet final state.

Installing the BoostedWAnalysis Package

The package for analysis of these samples is currently in a private Subversion repository in CERN AFS space. To request access, send an email to Michael Wilson <mgwilson at cern.ch>

1. Download and install ROOT from http://root.cern.ch/drupal/content/downloading-root. It is recommended to install version 5.20/00 or later. (I had a weird plotting problem in 5.22 — MGW.)
2. Set the ROOTSYS environment variable to the installation path.
3. Create a new empty directory for this analysis work. This directory will be referred to as the work directory.
4. cd to the work directory, install and compile an external fitting package, SlmPdfBuilder:
   

   svn co svn+ssh://lxplus.cern.ch///afs/cern.ch/user/m/mgwilson/svn/SlmPdfBuilder/tags/SlmPdfBuilder-01-05-05 SlmPdfBuilder
   cd SlmPdfBuilder ; make -f GNUmakefile.standalone dylib ; cd ..

5. cd to the work directory and install the ATLAS Athena package with the event definition:
   

   svn co svn+ssh://lxplus.cern.ch///afs/cern.ch/user/m/mgwilson/svn/AthIndepRec/tags/AthIndepRec-00-09-02 AthIndepRec

6. cd to the work directory, install and compile the analysis package, BoostedWAnalysis. On Mac OS X, do this:
   

   svn co svn+ssh://lxplus.cern.ch///afs/cern.ch/user/m/mgwilson/svn/BoostedWAnalysis/trunk BoostedWAnalysis
   cd BoostedWAnalysis ; make -f GNUmakefile.standalone dylib ; make -f GNUmakefile.standalone setup; cd ..

   On Linux, do this:
   

   svn co svn+ssh://lxplus.cern.ch///afs/cern.ch/user/m/mgwilson/svn/BoostedWAnalysis/trunk BoostedWAnalysis
   cd BoostedWAnalysis ; gmake -f GNUmakefile.standalone shlib ; gmake -f GNUmakefile.standalone setup; cd ..

7. Download some data. Files are located on the SLAC fileserver at CERN, pcphuat27.cern.ch, under the directory

• /u1/data/boostedW/AIR_14.2.25.8
  The acronym "AIR" stands for AthenaIndepRec; the number corresponds to the Athena version used to read the corresponding AODs. In this directory, choose the AthIndepRec version that corresponds to what you installed above.

1. The macros in the BoostedWAnalysis package assume certain directories; make the following symbolic links, if you have chosen to keep data or plots somewhere external to your work directory:
   

   ln -s <path/to/data> data
   ln -s <path/to/plots> plots
   ln -s BoostedWAnalysis/macros macros

Example use of the BoostedWAnalysis Package

If you have compiled the packages and have executed make setup as described above, the libraries should be loaded when you start ROOT from the work directory. The data files contain a number of TTree objects containing the indices for various arrays, like the array of jet algorithms or the array of triggers. To see which triggers have been considered, for example, run

• .x macros/PrintIndices.C("datafile.root","HLT")

To make some basic plots, edit the macros/MakeBasicPlots.C so that it looks in the correct place for your data files, and run it

• .x macros/MakeBasicPlots.C