raiders of the lost photons

E. Bissaldi – INFN Trieste, Italy / SLAC, USA 1

GLAST LAT Project IA Workshop 5 • August 29, 2005

Raiders of the Raiders of the lost photonslost photons

Elisabetta Bissaldi

University & INFN Trieste, ItalySLAC, USA

Gamma-ray Large AreaGamma-ray Large AreaSpace TelescopeSpace Telescope



OutlineOutline

• Introduction

• Photon selection with MC algorithm

• Results from cosmic ray data for integrated 2, 4 and 6 towers configurations

• Study of vertex topologies

• Summary



Photons

2 tracks = VERTEX

W

SI

SI

e+ e-

Topologies for DummiesTopologies for Dummies

Muons

NO VERTEX ?

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SI

SI

In TkrRecon: 1 track ≡ VERTEX



Often one of the 2 tracks is missing!

No Si hits No Si hits (edge)

Narrow separation Short track Compton angle scattering

Topologies in real lifeTopologies in real life

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SISI

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SISI



Original idea...Original idea...

• Bill Atwood’s talk presented at the 3rd IA Workshop in march 2005

• Develop finding algorithm:– Classification trees– Monte Carlo samples

I. AllGammaII. Surface Muons

– Cosmic ray data sampleIII. Test RUN 140001338

for single tower

candidates sample

(5% of triggers)



BB ChallengeBB Challenge

MC for 1 tower configuration

• Developed Initial selection cuts

• Defined 2 topologies

• Developed algorithm– classification trees

• Applied algorithm in data

MC for 2, 4, 6 towers configurations

Same

• Used only 1 topology

• Searched for simple cuts using main variables

• Applied cuts in data

• Studied vertex topologies

More details in the next slides...

BILL BETTA



• Same

• Focus on first topology

VtxAngle > 0.“VERTEX”

• Same

Initial selectionsInitial selections

• Initial conditions1. TkrNumTracks > 02. CalEnergySum > 10 MeV

• Definition of 2 topologies

3. VtxAngle > 0. VtxAngle ≡ 0. “VERTEX” “1TRACK”

4. Tkr1ToTFirst > 1 MIP

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SI

SI

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SI

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SI

SI



Additional variablesAdditional variables

5. Tkr1SSDVeto > 1

Use Tracker in self Veto Mode to replace ACD At least one hit plane before start of track

Calorimeter

Electronics

Found track

Track projection

same



Bill’s Classification TreesBill’s Classification Trees

Variables used to select :

a) Tkr1ToTTrAveb) Tkr1Chisqc) Tkr1SSDVetod) Tkr1TotFirste) Tkr2Chisqf) Tkr2FirstChisqg) CalEnergySum

* From Bill’s talk

*

VERTEX TOPOLOGY



Betta’s MC/DATA samplesBetta’s MC/DATA samples

I. MC AllGamma

– 1 x 106 events– 33341 trig. events– Isotropic– 18 MeV – 18 GeV

v5r0608p7

II. MC Surface Muons

– 4 x 106 events– 219322 trig. events– Isotropic– PDG formula and low

energy extension v5r0608p7

III. DATA Cosmic Rays

– 2 Towers: RUN 135002134 (462678 trig. events) v5r0608p6





all cuts

no cuts

Tkr1SSDVetoTkr1SSDVeto

MC Muons

all cuts

no cuts

MC All Gamma

Tkr1SSDVeto>2 ?

TkrNumTracks>0CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1Tkr1SSDVeto>1




no cuts

MC Muons

no cuts

MC All Gamma

all cutsall cuts

We lose 10% of photons and 70% of muons





no cuts

all cutsall cuts

no cuts

MC All Gamma DATA

We lose 10% of cosmic ray data




Tkr1ToTTrAveTkr1ToTTrAve

no cuts no cuts

all cuts all cuts

MC All Gamma MC Muons

Tkr1ToTTrAve>1.3?




no cuts no cuts

MC MuonsMC All Gamma

all cuts all cuts

We lose 5% of photons and 70% of muons

TkrNumTracks>0CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1Tkr1SSDVeto>1Tkr1ToTTrAve>1.3




no cutsno cuts

MC All Gamma DATA

all cuts all cuts

We lose 20% of cosmic ray data

TkrNumTracks>0CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1Tkr1SSDVeto>1Tkr1ToTTrAve>1.3




2 Towers Results2 Towers Results

MCAllGamma

MCSurface muons

DATACosmic rays

STEPSN°

events%

N° events

%N°

events%

No cuts 33341 100 219322 100 462676 100

1 47 98 97

2 19 33 32

3 9 1.5 3

4 5.7 0.05 1.6

5 5.3 0.03 1.3

6 1672 5.0 25 0.01 4715 1.0Cuts are cumulative!

TkrNumTracks>0+CalEnergySum>10. +VtxAngle>0. +Tkr1TotFirst>1+Tkr1SSDVeto>2+Tkr1ToTTrAve>1.3

Similar results were obtainedfor 4 and 6 towers!(ask me later)




100 %

10 %

1 %

0.1 %

0.01 %

STEPS 1 2 3 4 5 6

5

1

0.01

MC AllGamma

DATA

MC Muons

VtxAngle>0.

Tkr1SSDVeto>2

Cuts are cumulative!

Tkr1ToTTrAve>1.3



candidates with Event Displaycandidates with Event Display

tracks

dir

hitW

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SI

tracks

dir



tracks

dir


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tracks

dir



DifferentVertexTopologies tracks

dir


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SI

SI

tracks

dir



Topologies à la carteTopologies à la carte

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tracks

dir

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tracks

dir

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SI

tracks

dir

DOCA = Distance Of Closest Approach



Vertexing Variable in the Merit Ntuple Summary of track composition and topology

?

VtxStatusVtxStatus

no cuts

MC All Gamma 2 Towers



Single track vertex

2 tracks vertex

More than 2 tracks in

vertex

Vertex positionset by

DOCA point

Vertex tracks share first hit

Vertex tracks start in

different planes

DOCA pointlies inside track hits

VtxStatus Values

0 1 2 3 4 5 6 7

01 1

1 161 1 34

1 641 1 80

1 1281 1 1 162

1 1 1921 1 1 208

VtxStatus bit patternVtxStatus bit pattern

21 + 25 + 27 = 162

1=true



VtxStatus DistributionsVtxStatus Distributions

MC AllGamma 2 Towers

no cuts all cuts

0 and 1

01

162128

43 %28 %12 % 7 %

16234

12816

55 %14 %11 %8 %

162

2.7 % of initial triggers!



...and with DATA...and with DATA

DATA Cosmic rays 2 Towers

no cuts all cuts

1162

0

86 % 6 % 3 %

16234

128

59 %13 %7 %

0 and 1162

0.6 % of initial triggers!



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SI

SI

VtxStatus = 1622 tracks vertex, vertex tracks share first hit and DOCA pointlies inside track hits

tracks

dir

My friend 162My friend 162

tracks

dir

hit

hit



Energy distributionEnergy distribution

DATA 2 Towers

all cutsVtxStatus=162

all cutsVtxStatus=162

MC AllGamma 2 Towers

TkrNumTracks>0CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1Tkr1SSDVeto>1Tkr1ToTTrAve>1.3VtxStatus=162



SummarySummary

• Developed a simple algorithm to select in cosmic ray data using Bill’s analysis as a starting point

• Learned about how different the topologies are from the simple picture from pair conversion

• Future Work: Possibility to use the selected sample to study the

behaviour of the detector with different register configurations Depending on the physics analysis, we may be more

interested in selected vertex topologies Explore this further in my thesis Analysis of reprocessed 4, 6 and 8 towers in progress...



GRAZIE...GRAZIE...

• Eduardo• Bill

• Francesco• Anders• Leon• Eric• Luis

...all other italian summer students and people I met at SLAC!



Backup slidesBackup slides




AllGammaSurface muons

Cosmic Data 75

Cosmic Data 77

STEPSN°

events%

N° events

%N°

events%

N° events

%

Recon 89638 100 558757 100 390033 100 389690 100

1 57 98 92 92

2 31 51 45 45

3 15 2 5 5

4 13 0.3 2 2

5 10335 11.5 983 0.18 7588 1.9 7499 1.9




Cosmic Data RUN 135004075


Applied cuts N° events % N° events %

Recon 390033 100 389690 100

1. 92.4 92.4

2. 45.5 45.4

3. 10.6 10.7

4. 28.2 28.1

5. 62.9 63.1

1.+2. 44.7 44.6

1.+2.+3. 4.6 4.6

1.+2.+3.+4. 2.4 2.3

1.+2.+3.+4.+5. 7588 1.9 7499 1.9




AllGamma Surface muons

Applied cuts N° events % N° events %

Recon 62070 100 391538 100

1. 54.2 97.2

2. 71.2 48.6

3. 28.1 4.9

4. 43.9 6.9

5. 46.6 63.8

1.+2. 27.2 45.9

1.+2.+3. 14.0 2.1

1.+2.+3.+4. 10.1 0.2

1.+2.+3.+4.+5. 6171 9.9 608 0.1





Applied cuts N° events %

Recon 61994 100

1. 97.0

2. 43.4

3. 14.7

4. 31.2

5. 67.6

1.+2. 42.7

1.+2.+3. 6.3

1.+2.+3.+4. 3.1

1.+2.+3.+4.+5. 1533 2.5




STEPS 1 2 3 4 5

100 %

10 %

1 %

0.1 %

AllGamma

Data 75Data 77

Muons11.5

1.9

0.18




100 %

10 %

1 %

0.1 %

STEPS 1 2 3 4 5

9.9

2.5

0.1

AllGamma

Data

Muons



MC Surface Muons

no cuts

0 and 1

10

92 %3 %

Same with MC Muons...Same with MC Muons...

raiders of the lost photons

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