LHCb DaVinci Tutorial

This hands on tutorial should be followed by all newcomers to the LHCb physics analysis software. The purpose of these exercises is to allow you to write a complete though simple selection algorithms for a typical decay: B_s → J/ψφ. The exercises covers the following topics:

It is assumed that you are familiar with the basic tutorial. You are also invited to register to the lhcb-davinci and lhcb-distributed-analysis mailing lists.

The basic part of this tutorial has last been tested with DaVinci v33r7 release candidate (meaning it was not yet out) and Tutorial/Analysis v10r6. Important message: PLEASE REPORT ANY MISTAKES. Unfortunately we cannot guarantee that all tutorials always work out of the box.

Talks

There are talks covering the tutorials. Use the latest version if available.

• 21 October 2013 PPTS: Two talks about Decay Finders and BackgroundCategory (relates to Tutorial 6): Agenda.
• October 2012 Analysis Week. Covers Tutorials 0 and 8: Agenda.
• April 2012 Analysis Week. Covers uDST and RooStats: Agenda.
• March 2011 LHCb week. Covers Tutorials 0 and 8: Agenda.
• January 2011 UK Software Course. Agenda.
• December 2010 LHCb week. Covers Tutorials 0 and 8: Agenda.
• October 2010 LHCb week. Covers Tutorials 0 and 8: Agenda.
• February 2010 Software week. Covers Tutorials 0 and 4 (DaVinci v24r7p3): Agenda.
• January 2010 Cambridge Tutorial : Overview of LHCb Software, primarily aimed at analysis (DaVinci v24r7, Ganga and Python). Agenda.
• October 2009 Software Week Tutorial. Covers tutorial 1 and an introduction to the DaVinci configurable with DaVinci v22r1 . Agenda.

Prerequisites

You will need to be familiar both with C++ and python. After that you will need to do AT LEAST the following tutorials before starting the DaVinci tutorial.

• Introduction to LHCb software - part 1 - Software organisation, environment setup and CMT
• Introduction to LHCb software - part 2 - Algorithms, Printing, Job Options.
• Ganga Tutorial - Getting started with Ganga. Ganga Tutorial for LHCb, last updated 2009-03-16, using DaVinci v22r1

It would be very beneficial if before attending the DaVinci tutorials you have tried the GaudiPython python pre-requisites exercises

Pop Quiz:

If you know the following concepts you should be OK in this tutorial:

• What is a pure virtual baseclass in C++?
• How can you loop over a dictionary in Python?
• What does CMT stand for?
• What will SetupProject --build-env do for any project?
• How do you set the OutputLevel for a GaudiAlgorithm?
• If you have a checked out project how do you build it?
• What is Dirac, and what does CMTCONFIG=x86_64-slc5-gcc43-opt mean?
• How can you resubmit all failed subjobs in Ganga?

Exercises

There are many exercises available all based on the Tutorial/Analysis package. Latest version is v10r6 (for DaVinci v33r7). The excercises are divided into a fast-track Introductory set, and an Advanced set if you wish to see and program the C++.

Getting Started:

• DaVinciTutorial0 : Introduction: Running DaVinci for the first time, and the XMLSummarySvc.
• DaVinciTutorial0p5 : Introduction: Preparing the tutorials and a ganga job to run them.

Getting your hands dirty:

• DaVinciTutorial8 : Introduction: Run on a stripped DST (uses some of 6, but not 4).
• DaVinciTutorial6 : Introduction: Fill an NTuple with MC truth, tagging and trigger info (requires 4 or 8, not 5).
• DaVinciTutorial7 : Advanced: DecayTreeTuple (requires 6).
• DaVinciTutorial4 : Introduction: write a full Bs->J/psi Phi selection chain using the selection "framework" and no C++.
• DaVinciTutorial5 : Introduction: Use some debugging tools (requires 4).
• DaVinciTutorial9 : Introduction: Use the Dictionary Tools to add a multivariate classifier to your selection (requires 4).
• DaVinciTutorial9a: Advanced: Adding a custom multivariate algorithm to the MVADictTools. (requires 9)
• DaVinciTutorial9b: Advanced: Applying arbitrary functors to a kinematically refitted decay tree. (requires 9)
• DaVinciTutorial1 : Advanced: write a simple algorithm looping over all muons and filling some plots.
• DaVinciTutorial2 : Advanced: extend the algorithm to make a J/psi in C++ (requires 1).
  • Do this exercise if you plan to reconstruct a decay chain writing your own C++ code. The recommended way of doing this is explained in 4.
• DaVinciTutorial3 : Advanced: extend the algorithm to be able to also make Phi's (requires 2). A bit more about C++.

We recommend you start with DaVinciTutorial0, followed by DaVinciTutorial0p5 to learn ganga. Then go to DaVinciTutorial8 as this is most likely what you'll need first.

Related additional tutorials:

• DebuggingDaVinci: Introduction: How to debug and read DaVinci log files
• DaVinciConfigurable: Introduction: How to steer the job in DaVinci.
• GaudiPythonTutorial : Advanced: Use GaudiPython, to do simple analysis on reconstruction objects stored on a DST. Write a Bs -> J/Psi Phi selection MicroDST. Use GaudiPython to do simple analyses on the stored candidates.

And Finally

• DaVinciTutorialTips : Introduction: Clean-up and get ready. Prepare for your own analysis!

More interactive Tutorials

• All tutorials in a big list.
• LoKi.
• Bender.
• GaudiPython.

-- PatrickKoppenburg - 22 Sep 2007 - 12 Jan 2009 -- PatrickSKoppenburg - 30-Sep-2013