Energy Flow Alrogithm Development for a Digital Hadron
Calorimeter Using GEM Venkatesh Kaushik*
University of Texas at Arlington
• Motivation• Digital Hadron Calorimetry• Why GEM ?• Energy Flow Analysis• UTA GEM, DHCal Study• Plans for the Future• Conclusion
Venkat, TSAPS Meet Oct 10 - 12, 2002
*On behalf of the HEP Group at UTA
Motivation• New techniques are needed to achieve
physics goals at future accelerators, such as the Next Linear Collider (NLC)
• Limitations of traditional sampling calorimetry
• Need for efficient tracking and jet energy resolution
• Digital calorimetry with efficient tracking is the future ?
• Physics motivation for Higgs characteristics
Venkat, TSAPS Meet Oct 10 - 12, 2002
Digital Hadron Calorimetry
• Small cell size for good multiple track shower separation
• High efficiency for MIP’s in a cell for effective shower particle counting
• Possibility for multiple thresholds• Dense and compact design for quick shower
development to minimize confusion• Large tracking radius with optimized magnetic field for
sufficient separation between tracks for shower isolation
Venkat, TSAPS Meet Oct 10 - 12, 2002
Why GEM?• Allow flexible and geometrical design, using printed
circuit readout • High gains, > 104, with spark probabilities per incident
less than 10-10
• Fast response
– 40ns drift time for 3mm gap with ArCO2
• Relative low HV– A few 100 volts per each GEM gap compared to
10-16kV for RPC• Reasonable cost
– Foils are basically copper-clad kapton
Venkat, TSAPS Meet Oct 10 - 12, 2002
WHY .. Another Algorithm ?
Venkat, TSAPS Meet Oct 10 - 12, 2002
• Many interesting events have 2 or more ( as many as 10 !!) jets in the final state
• Require better than 40%/E for meaningful Higgs self-coupling measurement
• Good clustering technique needed to resolve showers which possibly overlap in complex events
• Hadronic showers tend to be more broad and unconnected -- tough to handle.
• Pattern recognition is crucial to associate energy deposited in the calorimeter cells with particles
The Need…
Venkat, TSAPS Meet Oct 10 - 12, 2002
Typical Composition of Jets
Components of Jets
Fraction of Energy in %
Detector
Charged particles 60 Tracker
Photons 20 EM calorimeter
Neutral Hadrons (K0
L,n)10 EM and Hadronic
calorimeter
Neutrinos 10 Lost
Venkat, TSAPS Meet Oct 10 - 12, 2002
Energy Flow Algorithm
C 2
C 3
C 5
C 7
C 4
C 6
C 1
Normal Calorimetric Method
p2p3 p5p7
Energy Flow Method nCpE ij
Only part susceptible to shower statistical fluctuations
Venkat, TSAPS Meet Oct 10 - 12, 2002
ij CE
e+e- hZ bbjj Event
Venkat, TSAPS Meet Oct 10 - 12, 2002
Resolving Power
• Essential to resolve and associate clusters with charged particles for effective removal and replacement of the cluster energies
• Finer segmentation provides higher resolving power
• Tracking for muons• Look for late decays
Venkat, TSAPS Meet Oct 10 - 12, 2002
2 Clusters
Jet Energy Resolution
Venkat, TSAPS Meet Oct 10 - 12, 2002
Courtesy: H.Videau
60%/E 30%/E
Using EFA
UTA DHCal and GEM studies
GEM Detector Prototype built
Test chamber box
Readout circuit board (1cmx1cm pads) being redesigned
HV layout design complete
Courtesy: J.Li
Venkat, TSAPS Meet Oct 10 - 12, 2002
UTA DHCal and GEM Studies
Existing Geometry of DHCal 8 staves each having 5 modules Each module has 40 layers, each
layer with plates of 18 mm of Fe and 6.5 mm of polystyrene scintillator
Hcal hits are collected Polystyrene scintillator, in cells of ~1 cm2
Hcal end-caps are build as 32 side Polyhedrons, with 40 layers inside, each layer with plates of 18 mm of Fe and 6.5 mm of Polystyrene scintillator
Venkat, TSAPS Meet Oct 10 - 12, 2002
Courtesy: Paulo deFrietas
UTA DHCal and GEM Studies
TDR / Hcal02 Model chosen for modification
Fe-GEM sub-detector instead of
the existing Fe-ScintillatorNew driver for the HCal02 sub-
detector moduleLocal database connectivity for
HCal02Courtesy: Paulo deFrietas
Venkat, TSAPS Meet Oct 10 - 12, 2002
Plans for the Future
• Construct thicker prototype for beam exposure if the studies turn out feasible
• Work on understanding discharge probability of GEM
• Perform Clustering Algorithm Study• Perform Tracking Algorithm Study• Work on GEM geometry implementation for
design optimization
Venkat, TSAPS Meet Oct 10 - 12, 2002
Conclusion
• Future physics goals demands higher jet energy resolution calorimetry
• Energy Flow method supplemented with digital calorimetry is a viable solution
• A good project for strategic preparation of the future of the group
• The software (MC and tracking algorithm) will be beneficial to other future projects
• This first year will provide a firm foundation for further studies to develop the DHCal technology
• LC calorimeter group is very supportive on this initiative• We believe this study will be fruitful in the future
Venkat, TSAPS Meet Oct 10 - 12, 2002
