This lesson is being piloted (Beta version)

Glossary

Key Points

The Physics
  • We will be studying the reconstruction of the Higgs decaying to a pair of b quarks.

  • The dijet invariant mass (m(jj)) is the key observable.

  • The code we will be using is not intended for a full-fledged analysis.

Setting up the ATLAS Environment
  • A software release (e.g. AnalysisBase) is necessary to analyze ATLAS data.

  • You will learn much more about the details of an ATLAS release on Tuesday!

  • The UChicago Analysis facility will serve for all ATLAS work throughout this tutorial.

  • Docker serves as a “portal” for all ATLAS work, that is to say we can do the same work as in the facility. It can be thought of a “virtual machine”.

  • You will learn much more about Docker on Wednesday!

Obtaining The Test Files
  • An AOD and DAOD file are the same thing, but a DAOD has “what you want”.

  • The input file container name gives you a lot of nice information about how the file was produced.

  • You can inspect a file using native ROOT, and looking at CollectionTree or using the checkxAOD.py executable within the release.

Running the Basic Analysis
  • The directory where your source code lives and where you build the code are two separate directories.

  • When in doubt, you can always remove the entire contents of your build directory.

  • Information within the (D)AOD is organized in what is called the EDM.

  • Compiling/linking ATLAS code “by hand” is super long. Thank goodness we have CMake.

  • Judiciously choose when to parameterize your ignorance. It is a powerful approach, but remember you are a smart human, not a robot.

Building With CMake
  • CMake is easier … when it works.

  • You will learn all the ins and outs of CMake on Tuesday. For now, it can function as little more than a tool to circumvent the long g++ commands.

Your First Plot
  • The m(jj) spectrum is peaked near the Higgs mass of ~125 GeV.

  • There seems to be a long tail on the high mass side.

  • Important Tool 1 - We examine data via a “projection” onto histograms (TH1 in ROOT).

  • Important Tool 2 - Much of what we study in analysis is the behavior of four-momenta (TLorentzVector in ROOT).

Extra Exercises
  • Writing good code requires care, especially when it gets complicated.

  • Using configuration files allows us to compile our code less frequently.

  • The search for VH(bb) is hard!

Glossary

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