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A First DC2 Analysis with New Recons

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DC1 Recap

Recon Re-write Review

TkrRecon

CalRecon

Good Energy Analysis

PSF Analysis

THIS IS A PROGRESS

REPORT

ALL ANALYSIS ARE

PRELIMINARY

Eff. = 82%

Cuts: 2/1

Cuts: 1/1

Bad-Cal = 4.5%

Meets SR

Events Eff.: 94.5%

Ratio 95/68 > 3

Cuts: 3/4

Cuts: 3/2

Events Eff.: 52.3%

Events Eff.: 19.1%

DC1 Recap

An extensive analysis was performed

to optimize PSF and energy resolution

while maintaining the maximum Aeff.

This was the first complete analysis

done using the Geant 4 Simulation

(previous Glast Analysis used the

Gismo simulation)

Background Rejection in DC1

3 Classes of Background after selection

for good energy and direction

reconstruction

Prob. g > .5

Upward moving events

Earth Limb events

Downward moving events

Prob. g > .9

A Classification Tree analysis was constructed

allowing cutting on the probability that an event

was a g (vs. Background)

However – to meet the Science Req. for Background

contamination – the remaining Aeff was lower then

the goal (it did meet the Sci. Req.)

Conclusions from DC1

The Status of the Reconstruction in GLAST was marginal

1) The code had been patch, re-patched, etc. many times

2) The code had become needlessly complex and

essentially un-maintainable

3) The algorithms (particularly for the Calorimeter) were

undeveloped

Major Effort was Launched to completely re-write

the Tracker and Calorimeter Recon

1) Emphasis on uniformity and simplicity

2) Migrate related task to one area

3) Re-vamp and re-assess poorly functioning

algorithms (esp. Vertexing and Calorimeter)

TkrTrackParams

TkrTrackHit

TkrTrack

TkrFitHit

TkrFitMatrix

TkrFitPar

TkrFitPlane

TkrFitTrackBase

TkrKalFitTrackBase

TkrKalFitTrack

TkrPatCand

TkrPatCandHit

TkrRecInfo

TkrTrackTab

Tracker Recon Re-write

External Controls

Program architecture simplified

New Vertex Algorithm

Vertex Location

Combining Tracks

Multivariate Averaging:

- Preferred Solution
- If 2 Tracks share the same first hit

Put Vertex

at Radiator

Mid-Point

W RADIATOR

SSD PLANE

SUPPORT PANEL

Found

Tracks

Put Vertex

DOCA Point

SUPPORT PANEL

where Piare the parameter vectors of the combination (Pair) and tracks (P1 and P2)

and Ciare the covariance matrices

where

- Next Best Solution
- If DOCA location of 2 tracks
- lies before 1st Hit

W RADIATOR

SSD PLANE

All Other Case

Put Vertex at Z location

of start of the 1st Track

Found

Tracks

The parameter vectors are (x, Sx, y, Sy)

CalRecon Re-write

1) Put GLAST’s Fracture Energy Back Together

1 GeV g

Thin Radiator

Hits

Gap Between

Tracker Towers

Thick Radiator

Hits

Blank Radiator

Hits

Gap Between

CAL. Towers

Calorimeter

Xtals

Leakage out

CAL. Back

2) Better Background Rejection Cuts

Shower Shape parameters

3) Move code to where it belongs!

AnalysisNtuple CalRecon

CalRecon Re-write (cont.)

A Major Change: Replace Layer-by-Layer Analysis with Energy-Moments

Energy Moments: Same as Classical Mech. Mass moments with energy

replacing mass (see Goldstein) (first used by S. Ritz in GLAST)

Long. Moment

Trans. Moment

Moments

LSQ Fit to Layers

Good Energy Analysis

- Initial Cuts:
- CalEnergyRaw > 5 MeV and
- CalCsIRLn > 4 rad. len.
- 2) Tkr1ZDir < -.2 (FoV)

But First: The New Data Sets

- Major effort by many people

- Took a couple of shots to get right

- 1.5x106 All Gamma*

run 23-June-2005

- 6 x106 Orbit-Average Background

run 24-June-2005

- All data run on SLAC Batch Farm

available at GLAST ftp site

- These are the first large data sets

using new Recons

color range: 0 - 150

Pruning Selections:

1) TkrNumTracks > 0 standard mode

2) TkrNumTracks = 0 Cal-Only Events!

*All Gamma: 2p str. , 18 MeV – 180 GeV,

1/E Spectrum

Energy Assessment

EvtDeltaEoE =

was EvtMcEnergySigma

Top plots show dep. on

MC parameters

Bottom plots show dep. on

Recon parameters

Data divide into Energy Ranges using CalEnergyRaw

HiCal

MedCal

LowCal

350 - 3500 MeV

CalEnergyRaw > 3500 MeV

CalEnergyRaw < 350 MeV

- Produce a set of variables that are ~independent of cos(q) and E
- Parametric functionof Tkr1ZDir and EvtLogEnergy
- Define Class "GoodEnergy" & "BadEnergy"
- GoodEnergy: (will explore dependence on this)
- 2) Derive a CT for each of the EvtEnergyRaw Bins

Low CAL

more Energy CT Details

Med CAL

High CAL

100

100

100

80

80

80

60

60

60

40

40

40

20

20

20

0

0

0

Energy CT Dependencies

Since the energy resolution is improved – try more restrictive

definition of "Good Energy"

Eff.

DC1 Choice

Select this one

NOISE

Expected Behavior

Anomaly

Use of

Tkr1TotTrAve

in Cal Low CT

This is part of a problem at

High Energies .... more later

What's happening here?

Preliminary DC2 Energy Resolution

On Axis

Integrated Over FoV

DC1 Resolution

DC1 Resolution

DC2 Resolution

DC2 Resolution

High Energy

Deficit caused

by Pat. Rec.

Confusion!

Aeff x DW = 4.02 m2-str

Aeff x DW = 2.76 m2-str

Root Cause of Hi E Deficit

Pictures and Words....

Incoming g

Event #6

Bad Cal Dir

These events come from Old CalRecon

but effect remains.

First attempt to fix problem:

USE CAL DIRECTION

100 GeV g

Event #9

Bad Cal Dir

Incoming g

100 GeV g

Missed Track

Event #6

Bad Cal Dir

Clearly there's more

work to do here!

Missed Track

A First PSF Analysis for DC2

- Strategy: Divide and Conquer!
- Split Events in Thin and Thick
- Conversion locations
- For Events with > 1 Tkr. Vertices
- decide whether or not to use
- vertexed solution

Example: Thin Radiator – Vertex CT

More PSF CT Details

- Strategy: Divide and Conquer!
- 3) Find and tag (a la probability)
- Events with large PSFs

4) Finally – add a knob to describe

quality of reconstruction

- Using a REGRESSION TREE

Preliminary DC2 PSFs

Integrated over FoV

On Axis

DC2

DC1

DC2 Background Rejection

Nothing has been done with the recently run data.

(only became available late last Friday)

But – Here's is a peek –

Preemptory cuts:

1) GoodEnergy.Prob > .25

2) AcdDOCA > 250

3) Only Thin Radiator Events Analyzed so far

Data: 5.1x106 Orbit Ave. Bkg.

.75x106 All Gamma

15642 Events

942 Events (Good News)

more DC2 Background Rejection

more DC2 Background Rejection

Energy & Angle Compensate CalTransRms

Note: In AnalysisNtuple all variables beginning with

EvtE..... are previously defined variables which

have been compensated for log(E) and cos(q)

dependencies.

Conclusions

The 1st DC2 Workshop has already accomplished 90+%

its goals! - look at all the work it stimulated!

The Recon re-writes show good improvements in

- Energy Reconstruction

- PSF

- New Variables to Reject Background

The (first) large data samples are providing the next

level of insight in the Recons

- TkrRecon need more work in the area of

very High Energy reconstructions

- CalRecon needs MIP finding and more work

to refine moments analysis (emphasis on directions)