electromagnetic showers with the mst algorithm niels meyer the university of iowa matthew charles,...
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![Page 1: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/1.jpg)
Electromagnetic Showers with the MST Algorithm
Niels Meyer
The University of IowaMatthew Charles, Wolfgang Mader, Usha Mallik
ILC Workshop, Snowmass
August 17, 2005
● The MST algorithm● Classifying photons
● Status on efficiency & purity
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The Minimum Spanning Tree Algorithm
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 2
● Recursive algorithm● Any two hits with distance below a threshold end up
in the same cluster● User has to define distance definition and a threshold
Implementation for hep.lcd available in CVS(Matthew Charles, Wolfgang Mader, N.M.)
More details: “Calorimeter algorithms” sessions(Friday afternoon / Saturday morning)
![Page 3: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/3.jpg)
The Minimum Spanning Tree Algorithm
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 3
● Recursive algorithm● Any two hits with distance below a threshold end up
in the same cluster● User has to define distance definition and a threshold
Example:pion with ~4 GeVuse 3D distancethreshold = 0.75cm
![Page 4: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/4.jpg)
Finding Photons – Optimizing the MST
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 4
● Let's start simple, use 3D distance (no energy, angle, ...)Control sample: single particles (~1000 each) 1-10GeV in ECal barrel, SDFeb05 detector
● Find MIP tracks first, don't use these hits● Optimize threshold
by energy collected
2cm threshold~97% energy
1 2 3 cm
Energy fraction picked up
![Page 5: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/5.jpg)
MST Output
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 5
![Page 6: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/6.jpg)
MST Output
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 6
![Page 7: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/7.jpg)
Identify Photons
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 7
● Look at cluster properties, try to find simple cutsGoal: keep it simple for now!
SizeContentShapePosition
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Identify Photons
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 8
● Look at cluster properties, try to find simple cuts
SizeContentShapePosition
![Page 9: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/9.jpg)
Identify Photons
Niels Meyer ILC Workshow, Snowmass August 17, 2005Page 9
● Look at cluster properties, try to find simple cuts
SizeContentShapePosition
![Page 10: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/10.jpg)
Identify Photons
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 10
● Look at cluster properties, try to find simple cuts
SizeContentShapePosition
![Page 11: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/11.jpg)
Identify Photons
● Look at cluster properties, try to find simple cuts
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 11
SizeContentShapePosition
![Page 12: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/12.jpg)
Performance – Single Particles
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 12
● Photon efficiency:
● Accepts 5% pions, 10% neutrons, 10% K0L
98%
mean: 97%
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First Look at Overlap
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 13
● Life is always easy with single particles● Try pi0 (two close-by photons)
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First Look on Overlap
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 14
● Life is always easy with single particles● Try pi0 (two close-by photons)
![Page 15: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/15.jpg)
First Look on Overlap
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 15
● High energy efficiency is simple with single particles● Try pi0 (two close by photons)
![Page 16: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/16.jpg)
First Look on Overlap
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 16
● High energy efficiency is simple with single particles● Try pi0 (two close by photons)
![Page 17: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/17.jpg)
Test: Tighter Threshold
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 17
● Try threshold=0.75cm (continuous cluster)
![Page 18: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/18.jpg)
Test: Tighter Threshold
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 18
● Try threshold=0.75cm (continuous cluster)
![Page 19: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/19.jpg)
Test: Tighter Threshold
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 19
● Try threshold=0.75cm (continuous cluster)
Find ways to pick up more hits -
but now photoncores are known
![Page 20: Electromagnetic Showers with the MST Algorithm Niels Meyer The University of Iowa Matthew Charles, Wolfgang Mader, Usha Mallik ILC Workshop, Snowmass August](https://reader037.vdocuments.mx/reader037/viewer/2022102906/56649c9b5503460f94958a3e/html5/thumbnails/20.jpg)
Summary and Outlook
Niels Meyer ILC Workshow, Snowmass August 17, 2005 Page 20
● Use MST algorithm to find electromagnetic showers● Promising results on single particles and pi0● Work in progress:
● Stay tuned...
• Optimize energy collection efficiency• Find criteria for low-E photons• Study overlap with pions, neutral hadrons• ...• Put together a 'photon finder'