GLAST TDS Event Model

Introduction

Introduction

This document will describe GLAST Event Model for the Transient Data Store (TDS).

The Gaudi Transient Data Store is a mechanism to share data among multiple algorithms. An algorithm may take as input any data that is currently available on the TDS and then generate new data that is then stored on the TDS for other algorithms to use. Consider it a shared memory mechanism - similar in function to FORTRAN common blocks.

We store all data within the TDS: Monte Carlo (MC), digitization detector data, and reconstruction data.

Accessing data from the TDS

When accessing data from the TDS, it is recommended that one use the EventModel constant that is predefined for each path within the TDS, see the EventModel.cxx file. Thus, if our tree structure is modified in the future - your code will be unaffected. For example:
SmartDataPtr<McParticleCol> myVar(eventSvc( ), EventModel::MC::McParticleCol);

Data Object Table

Object Name	EventModel Constant Access	Description
Event	EventModel::EventHeader	Event Header: run, id, time
McParticleCol	EventModel::MC::McParticleCol	Collection of MC Particles
McPositionHitCol	EventModel::MC::McPositionHitsCol	Collection of MC PositionHits
McIntegratingHitCol	EventModel::MC::McIntegratingHitsCol	Collection of MC IntegratingHits
AcdDigi	EventModel::Digi::AcdDigiCol	digitized ACD detector data: IDs, PHAs
CalDigiCol	EventModel::Digi::CalDigiCol	digitized CAL detector data
TkrDigiCol	EventModel::Digi::TkrDigiCol	digitized TKR detector data
AcdRecon	EventModel::AcdRecon::Event	ACD reconstruction data
CalXtalRecCol	EventModel::CalRecon::CalXtalRecCol	ObjectVector of CAL crystal reconstructed data
CalClusterCol	EventModel::CalRecon::CalClusterCol	Vector of all clusters found by CAL recon.
TkrClusterCol	EventModel::TkrRecon::TkrClusterCol	Container of clustered silicon strip hits in the Tracker.
TkrPatCandCol	EventModel::TkrRecon::TkrPatCandCol	Vector of pattern recognition track candidates.
TkrFitTrackCol	EventModel::TkrRecon::TkrFitTrackCol	Vector of fit tracks.
TkrVertexCol	EventModel::TkrRecon::TkrVertexCol	Vector of "vertices."

Accessing Ntuple Data

The ntuple data is also stored on the TDS. Accessing that data is different from obtaining other data. Please see this page for details.

Introduction

What is the TDS?

Data Object Table

Accessing Ntuple Data