Standard N-tuples

Contents

• Introduction
• Getting Data
• Analyzing Data

Introduction

• Ntuple data is contained in files ending with .sntp.R<release>.root (full ntuples) and .snts.R<release>.root (slim ntuples).
• There are also Cambridge ntuples (produced as the end product of Cambridge Reconstruction), and Analysis Ntuples, deriving from Standard Ntuples.

Each Standard Ntuple file contains one or more ntuples, each in the form of a ROOT TTree.

The ntuple trees produced during production (up until R1.14) were:

• NtpSR containing a summary of the standard reconstruction results.
• NtpMC containing a summary of the mc truth information.
• NtpTH containing "truth helper" information which can be used to match reconstruction results with the mc truth entity which has the strongest association to that reconstruction result.

These 3 ntuples have been replaced in production running with a single ntuple TTree (as of R1.14):

• NtpSt contains all data previously stored in the 3 separate ntuples.
• The 3 separate ntuples are maintained and although not produced in production running, can be produced in user's individual jobs.

• CandNtupleSR
• MCNtuple
• TruthHelperNtuple

Getting the Ntuple Data

• .sntp files store the full ntuple results. These files are accessible through a tape robot mechanism to retrieve data from Fermilab mass storage (ENSTORE).
• .snts files store the "slimmed" down version of the ntuples. The content is the same as the .sntp files, except the strip information has been removed. These files are available on afs space at FNAL.

Links related to Getting the Ntuple Data

• Retrieving Data From Fermilab is a useful link describing general instructions on how to retrieve MINOS data from both ENSTORE and afs space at Fermilab.
• Farm Production Statistics is a useful link to determine which files have been produced by production running, including the ntuples files, and their location.

Analyzing the Ntuple Data

• ROOT TBrowser
  • Useful for very simple displays of data. Documentation of how to browse TTrees can be found in the ROOT user manual.
• TTree::Draw,Scan, etc. executed at ROOT prompt.
  • Useful for very simple displays of data.
  • Documentation of use in ROOT user manual and also Roy Lee's Numi note 860. Some simple examples can be found on the ntuple example web site. (See links below).
• TTree::MakeClass/MakeProxy
  • MakeClass generates skeleton analysis class for tree.
  • Useful in cases where analysis of data is more complex.
  • Documentation of MakeClass use in TTree class documentation. MakeProxy is described on the ntuple example web site with some examples of use.
• "C++" rootcint script
  • Useful for complex analysis of ntuple data. Especially those which require embedded loops, e.g. looping over strips associated with tracks associated with events associated with the snarl.
  • Examples on the ntuple example web site.
• Read ntuples back in through framework and analyze with a job module.
  • Useful for complex analysis of ntuple data.
  • Ntuple records can be read in like any other record type back into the job framework. Specify input stream "NtpSt".
  • The AnalysisNtuple package takes this approach - the standard ntuples are read back into the framework and a condensed analysis ntuple is generated as output.

Links related to Analyzing the Ntuple Data

• Since the ntuple data structure is ROOT TTree, a useful place to begin to understand how to analyze the TTree is to read the related ROOT documentation. In particular:
  • The Trees chapter of the ROOT User's Guide

  • The reference guide to TTree
    Scroll through and look at TTree:Draw and TTree:AddFriend etc.

• There is an Ntuple chapter in the minossoft UserManual.

• Ntuple Example Site
  This site contains examples of how to use the MINOS ntuples. It includes a description of ROOT's latest analysis tool: MakeProxy.

• Analysing a loon job results with ROOT
  Several videos and a tutorial showing how to analyse ntuple files.

• Numi Note 860
  A NUMI note written in April 2003 by Roy Lee that describes his n-tuple which formed the basis of the current standard ntuples.

• NTuple Graphing Help
  A very brief summary showing how to produce a histogram with a cut.

• Glossary of Leaf Meanings in the NtpSR Tree
  This was written by Phil Symes and Sue Kasahara back in August 2003.

• The ntuple class header files, for example, CandNtupleSR/NtpSRRecord.h, have comments describing the meaning of the different data members. The Glossary meanings were derived from the header class comments, but the header class comments are kept more up-to-date.

• The UserManual MC Info chapter, by Mike Kordosky, is a useful collection of definitions of some of the data members stored in NtpMC.