1. Instrument Analysis Workshop II
Gamma-ray Large Area Space Telescope
Data Analysis 101
Bill Atwood
SCIPP/UCSC
Instrument Analysis Workshop II
27-Sept-2004

2. Modes of Working Recon Root Files:
All the information – not a tabular structure
- All the tracks
- All the hits on each track
- Etc.
Large Files – Root Macros
nTuple:
Key information distilled from Root Files
Flat Tabular structure (Xcel Spread Sheet)
Large number columns – to make possbile
an "in-depth" view of data
SVAC:
Some of both

3. What Each Mode can be used for
Root Files: Full analysis
- Projection of tracks into subsystem of interest
- In case of Gleam environment – Full power of
geometry (no hard coding of numbers!)
nTuple:
- Many parameters of track trajectories present.
Allows of simple projections into subsystem.
(geometry must be entered by hand!)
- Allows for correlation between variables to be
studied.

4. My own style:
- Develop Plots of interest using nTuple
Often, must create new variables,
make projections, etc.
- Most variables of interest should not depend
on location or angles: Image the variable
Explore using scatter plots, profile plots, etc.
- Back results up into the Root oriented Analysis
Much of the Analysis Package evolved
in this manner.

5. Analysis Package
Purpose: Provide subsystem and system wide parameters for
Event Analysis
leit-motif: Provide a collection of templates and examples
on how to use the system (TDS & Services & Tools).
A set of classes where each class focuses on calculating
variables associated with a subsystem - or several together
All have names like McValsTool, CalValsTool, TkrValsTool,...

6. Image Example Require: Tkr1Gaps > 0 This is was the original idea
Image the Tracker Layout

7. Collapse down onto one
Tower
Cut off the edges
( 8 mm)
Collapse down onto one
SSD
Cut off the edges ...
( 4 mm)
These are the events that
shouldn't be... Lets Explore!

8. Require 1
Track
InEff. Events
Require
Small c2
Good Events
Require
a MIP

9. This suggests we require:
1) Tkr1Chisq < .2
2) .8 < CalMIPRatio < 1.2
3) TkrNumTracks == 1
Leaves: 4.1 K Events ( ~ 40% Efficiency)
This leaves 1 Ineff. Event

10. Goal: No Hard-Coded Geometry
Dual use of geometry:
Monte Carlo
Reconstruction
Method of Accessing:
Geometry Service
- Give global constants (size of tower, etc.)
Propagator
- Projects trajectories through 3D geometry
- Allows for error propagation, material audits,
etc.