Output

Introduction

All simulation output is in ROOT format. We convert the summary data into FITS. A description of the FITS data follows.

FT1

The current description of the FT1 as output from the DataChallenge simulation is available here:
FT1 Documentation

FT2

See: http://glast.gsfc.nasa.gov/ssc/dev/fits_def/definitionFT2.html

Introduction for ROOT

For those who desire to access the ROOT data directly, you will need to use an application capable of reading in ROOT files. The easiest path is to use the ROOT analysis environment. For more general information about ROOT and how we use it in GLAST, please see the GLAST ROOT home page.

ROOT Ntuple

Those of you familiar with the GLAST AO, will recall that the simulation output an ASCII ntuple. This file has now been replaced by a ROOT ntuple.

The data is tabular, where for each event, there is a fixed-length row of data. Each column corresponds to a particular ntuple element. The set of ntuple entries is defined in the following web page:

merit/AnalysisNtuple tuple

To read this ntuple, you need to use ROOT. It is recommended to use a version of ROOT >= 3.04.02. Version 3.04.02 is included with the binary distribution of the DataChallenge software.

ROOT Trees

Exposure

Please see the following web page: Exposure Tree

Detailed ROOT Trees

More complex data is also available as output. This data is stored in ROOT Trees. ROOT trees provide a mechanism to store objects. We currently support 3 types of ROOT trees: Monte Carlo, Digitization, and Reconstruction. Each contains the event and run numbers to allow unique identification of each event. The sections that follow describe each of the ROOT trees.

Monte Carlo

The Monte Carlo record is stored in a ROOT file using the mc ROOT classes. A full description of the Monte Carlo ROOT classes is available here.

Digitization

The resulting digitization data from all detectors is stored in the digi ROOT classes. A full description is available here.

Reconstruction

Another ROOT file may be created that contains more detailed reconstruction data. It contains tracks as determined by TkrRecon, energy reconstruction for each CAL log, and ACD DOCA values. A more complete description of the GLAST Recon ROOT file is available here.

H. Kelly Last Modified: 2003-12-03 17:42:44 -0800