1. SuperB computing mini-Workshop
Intelligent
Detector
Design
Norman Graf (SLAC)
SuperB computing mini-Workshop
Pearl Harbor Day, 2007

2. Linear Collider Detector Environment
Detectors designed to exploit the physics discovery potential of e+e- collisions at s ~ 1TeV.
Perform precision measurements of complex final states with well-defined initial state:
Tunable energy
Known quantum numbers & e─ , e+,  polarization
Possibilities for  , e─ , e─ e─
Very small interaction region
Momentum constraints (modulo beam & bremsstrahlung)

3. LCD Simulation Mission Statement
Provide full simulation capabilities for Linear Collider physics program:
Physics simulations
Detector designs
Reconstruction and analysis
Need flexibility for:
New detector geometries/technologies
Different reconstruction algorithms
Limited resources demand efficient solutions, focused effort.

4. Overview: Goals
Facilitate contribution from physicists in different locations with various amounts of time available.
Use standard data formats, when possible.
Provide a general-purpose framework for physics software development.
Develop a suite of reconstruction and analysis algorithms and sample codes.
Simulate benchmark physics processes on different full detector designs.

5. Fast Detector Response Simulation
Covariantly smear tracks with matrices derived from geometry, materials and point resolution using Billoir’s formulation.
Derivative of TRKERR.
Provides smeared tracks with full covariance matrix.

6. lelaps Fast detector response package.
Handles decays in flight, multiple scattering and energy loss in trackers.
Parameterizes particle showers in calorimeters.
Produces lcio data at the hit level.
Uses runtime geometry (compact.xml  godl).
An excellent tool for designing tracking detectors!

7. Lelaps: Decays, dE/dx, MCS
Ω- → Ξ0 π-
Ξ0 → Λ π0
Λ → p π-
π0 → γ γ as simulated by Lelaps for the LDC model.
gamma conversion as simulated by Lelaps for the LDC model.
Note energy loss of electron.

8. Detector Design (GEANT 4)
Need to be able to flexibly, but believably simulate the detector response for various designs.
GEANT is the de facto standard for HEP physics simulations.
Use runtime configurable detector geometries
Write out “generic” hits to digitize later.

9. Full Detector Response Simulation
Use Geant4 toolkit to describe interaction of particles with matter.
Thin layer of LC-specific C++ provides access to:
Event Generator input ( binary stdhep format )
Detector Geometry description ( XML )
Detector Hits ( LCIO )
Geometries fully described at run-time!
In principle, as fully detailed as desired.
In practice, will explore detector variations with simplified approximations.

10. LC Detector Full Simulation
MC Event (stdhep)
slic
Raw Event (lcio)
Geometry (lcdd)
Compact Geometry Description
(compact.xml)
GEANT4
Reconstruction, Visualization, …

11. Geometry System LCDD GDML Identifiers Sensitive Detectors
Regions
Physics Limits
Visualization
Magnetic Fields
Expressions (CLHEP)
Materials
Solids
Volumes

12. Geant4 Data Binding Area Root Element Geant4 Class(es)
Sensitive Detectors
<sensitive_detectors>
G4VSensitiveDetector
Identifiers
<iddict>
NA (custom classes)
Regions
<regions>
G4Region, G4VUserRegionInformation
Physics Limits
<limits>
G4UserLimits
Visualization
<display>
G4VisAttributes
Magnetic Fields
<fields>
G4MagneticField
Constants
<define>
NA (CLHEP expressions)
Materials
<materials>
G4Material, G4Element
Shapes
<solids>
G4VSolid
Volumes
<structure>
G4LogicalVolume, G4VPhysicalVolume

13. LCDD XML Format Container Elements <lcdd> <header>
<iddict>
<sensitive_detectors>
<regions>
<limits>
<display>
<gdml>
<define>
<materials>
<solids>
<structure>
<volume>
</structure>
<setup>
</gdml>
<fields>
</lcdd>
Core Elements
<idspec> – identifier
<sd> - sensitive detector
<region> – geometry region
<limitset> – set of physics limits
<vis> – visualization attributes
references
<fields>
GDML
Volume Extensions
<sdref> – reference to subdetector
<regionref> – reference to region
<limitsetref> – reference to limits
<visref> – reference to vis attributes

14. Volume Element <volume name=“EcalBarrelEnvelope”>
<materialref ref=“Air”/>
<solidref ref=“EcalBarrelTube”/>
<sdref ref=“EcalSD”/>
<regionref ref=“EcalBarrelRegion”/>
<limitsetref ref=“EcalBarrelLimits”/>
<visref ref=“EcalBarrelLimits”/>
<phsvol>
<volumeref ref=“EcalLayer1”/>
<physvolid id=“1”/>
</physol>
</volume>

15. Sensitive Detectors and Identifiers
<calorimeter name=“EMBarrel” hits_collection=“EcalBarrHits”>
<idspecref ref=“EcalBarrHits”/>
<projective_cylinder ntheta=“1000” nphi=“2000”/>
</calorimeter>
Identifiers
<idspec name="EcalBarrHits" length="54">
<idfield signed="false" label="layer" length="7" start="0" />
<idfield signed="false" label="system" length="6" start="7" />
<idfield signed="false" label="barrel" length="3" start="13" />
<idfield signed="false" label="theta" length="11" start="32" />
<idfield signed="false" label="phi" length="11" start="43" />
</idspec>

16. Regions, Fields & Limits
<region name="TrackingRegion"
store_secondaries="true"
cut="10.0"
lunit="mm"
threshold="1.0"
eunit="MeV">
<limitsetref ref=“TestLimitSet”/>
</regions>
<solenoid name="GlobalSolenoid"
inner_field="solenoid_inner_field"
outer_field="solenoid_outer_field"
zmin="solenoid_zmin"
zmax="solenoid_zmax"
inner_radius="solenoid_rmin"
outer_radius="solenoid_rmax"
funit="tesla"
lunit="mm"/>
Physics Limits
<limits>
<limitset name="TestLimitSet">
<limit name="step_length_max" particles="*“ value="1.0" unit="mm"/>
<limit name="track_length_max" particles="pi+, pi-, p0" value="100.0" unit="cm"/>
</limitset>
</limits>

17. Compact Description Example
Two different layer stacks in same Ecal.
<detector id="2" name="EMBarrel" type="CylindricalBarrelCalorimeter"
readdout="EcalBarrHits">
<dimensions inner_r = "150.1*cm" outer_z = "208.0*cm" />
<layer repeat="20">
<slice material = "Tungsten" thickness = "0.25*cm" />
<slice material = "G10" thickness = "0.068*cm" />
<slice material = "Silicon" thickness = "0.032*cm" sensitive = "yes" />
<slice material = "Air" thickness = "0.025*cm" />
</layer>
<layer repeat="10">
<slice material = "Tungsten" thickness = "0.50*cm" />
</detector>

18. SLIC Overview C++ user application using Geant4 toolkit
hub package  most of functionality implemented in subpackages
standard data formats for ILC
LCIO (output): HEP data model with generic Calorimeter and Tracker hits
StdHep (input): physics events
LCDD (input): GDML-based geometry system
command line or macro commands / interactive

19. SLIC Diagram Simulator for the Linear Collider (SLIC)
StdHep
Physics
Events
Simulator for the Linear Collider (SLIC)
Linear Collider Detector Description (LCDD)
Geometry Description Markup Language (GDML)
Linear Collider IO (LCIO)
reads
LCIO
Output File
SLIC
Geant4
Simulator
reads / writes
Reconstruction
&
Visualization
writes
reads
reads
LCDD
XML
Geometry
Compact
XML
Geometry
translated to

20. SLIC Commands All command-line options have equivalent Geant4 command
Sample command
slic -g geometry.lcdd -i events.stdhep -x -O -l LCPhys -r 1000
Equivalent macro
/lcdd/url geometry.lcdd
/run/initialize
/physics/select LCPhys
/generator/filename events.stdhep
/lcio/fileExists delete
/lcio/autoname
/run/beamOn 1000

21. Diagnostic Histograms
Diagnostic plots of event data
MCParticles, hits, clusters
Runs on different detectors
must have compact description
also need sampling fractions
Easy to use and setup
SLAC CVS project
cvs –d co SlicDiagnostics
./build.sh
./bin/SlicDiagnostics [...]

22. LCIO Overview Object model and persistency Events Monte Carlo Raw
Event and run metadata
Reconstruction
Parameters, relations, attributes, arrays, generic objects, …
All the ILC simulators write LCIO
Enables cross-checks between data from different simulators
Read/write LCIO from
Fast MC / Full Simulation
Different detectors
Different reconstruction tools

23. Physics Lists: LCPhys standard Geant4 EM physics hadronic models
Bertini Cascade
0 to 9.9 GeV for p, n, pi+, pi-
0 to 13 GeV for K+, K-, K0L, K0S, Lambda, Sigma+, Sigma-, Xi0, Xi-
Low energy parameterized models
9.5 to 25 GeV
Quark-Gluon String Model: use for
12 GeV to 100 TeV for p, n, pi+, pi-, K+, K-, K0L, K0S
additional neutron processes
neutron-induced fission
neutron capture
gamma-nuclear

24. Other Available Physics Lists
FTFC
Fritjof with CHIPS
FTFP
Fritjof with precompound
LHEP
low / high energy parameterised
QGSC
Quark-Gluon String with CHIPS
QGSP
Quark-Gluon String with precompound
QGSP_BERT
Quark-Gluon string with precompoind + Bertini Cascade
LHEP_BERT
low / high energy parameterised + Bertini Cascade

25. Event Sources General Particle Source (GPS)
advanced single particle source builtin to Geant4
angular distributions
randomized energy
one or more particles
generate in volume (box, tube, etc.)
StdHep
common binary format for event generators
HEPEVT block
your favorite event generator
PYTHIA, HERWIG, WHIZARD, etc.
LCIO
converts LCIO MCParticle block into G4PrimaryParticles
read output from other simulators (Mokka, JUPITER, etc.)
EXPERIMENTAL

26. Event Source Conversion
use LCIO MCParticle data structure for bookkeeping during simulation\\
GPS or G4ParticleGun
no initial MCParticle collection necessary
convert directly from Geant4 trajectory container
StdHep or LCIO event source
create initial LCIO MCParticle tree
make G4PrimaryParticles for each MCParticle if
travels > mininum tracking distance
intermediate or final (documentation not tracked)
predecays
preassigned decays from the generator
assign time, daughters, etc.
Geant4 may still override (e.g. if it interacts before predecay occurs)
no vertex  determined from parent particle

27. Software Distribution
SLIC requires
Geant4, CLHEP, GDML, LCDD, Xerces, LCPhys, LCIO
Automated build system provided
Binary downloads
Linux, Windows (Cygwin), OSX
All packages (dist) or just runtime dependencies (bin)
Or checkout and build from scratch
cvs –d co SimDist
cd SimDist; ./configure; make
Installed at SLAC, NICADD, FNAL, IN2P3, UC, ...
Report any problems to

28. GeomConverter
Small Java program for converting from compact description to a variety of other formats
LCDD
slic
lcio
GODL
lelaps
lcio
GeomConverter
Compact
Description
HEPREP
wired
org.lcsim
Analysis &
Reconstruction

29. Detector Variants
Runtime XML format allows variations in detector geometries to be easily set up and studied:
Stainless Steel vs. Tungsten HCal sampling material
RPC vs. GEM vs. Scintillator readout
Layering (radii, number, composition)
Readout segmentation (size, projective vs. nonprojective)
Tracking detector technologies & topologies
TPC, Silicon microstrip, SIT, SET
“Wedding Cake” Nested Tracker vs. Barrel + Cap
Field strength
Far forward MDI variants (0, 2, 14, 20 mr )

30. Example Geometries MDI-BDS Cal Barrel SiD SiD Jan03 Cal Endcap
Test Beam

31. Far forward calorimetry
Machine Detector Interface and Beam Delivery System
polycones
boolean solids

32. Summary
The American Linear Collider Physics Group simulation group has developed a suite of tools being used to design detectors for the ILC.
Flexible, fully-featured Geant4-based detector response simulator, slic, uses runtime detector geometry description.
Supports arbitrarily complex geometries (lcdd)
Many elements common to collider detectors are also available through a compact description
provides bindings to fastMC, visualization, reconstruction.

33. Additional Information
Wiki -
lcsim.org -
org.lcsim -
Software Index -
Detectors -
ILC Forum -
LCIO -
SLIC -
LCDD -
JAS3 -
AIDA -
WIRED -

34. Simulation Output
Uses LCIO, a lightweight persistency framework for LC simulations.
FORTRAN, C++ & Java bindings
Simulation produces collections of:
MCParticles
both generator-level and secondaries produced in Geant
SimTrackerHits
Full information about position-sensitive detectors
SimCalorimeterHits
Full information from showering detectors.

35. Tracker Hit MC Track producing hit
Encoded detector ID (detector dependent )
Global hit position at entrance to sensitive volume
Global hit position at exit of sensitive volume
Track momentum at entrance to sensitive volume
Energy deposited by track in sensitive volume
Time of track's crossing
Hit number
Local hit position at entrance to sensitive volume
Local hit position at exit of sensitive volume
Step size used by simulator in sensitive volume

36. Digitization x
Volume ID
dE/dx
x, p, t
Track ID

37. Calorimeter Hit Encoded detector ID (detector dependent )
MC ID, time and energy deposited by each contributing particle
Hit Number
Cell position
Radius, Phi, Z of cell
X, Y, Z of cell
Total energy deposited in cell

39. Maryland Physics Department Colloquium
xml: Defining a Module
<module name="VtxBarrelModuleInner">
<module_envelope width="9.8" length="63.0 * 2" thickness="0.6"/>
<module_component width="7.6" length="125.0" thickness="0.26"
material="CarbonFiber" sensitive="false">
<position z="-0.08"/>
</module_component>
<module_component width="7.6" length="125.0" thickness="0.05"
material="Epoxy" sensitive="false">
<position z="0.075"/>
<module_component width="9.6" length="125.0" thickness="0.1"
material="Silicon" sensitive="true">
<position z="0.150"/>
</module>
Maryland Physics Department Colloquium

40. xml: Placing the modules
<layer module="VtxBarrelModuleInner" id="1">
<barrel_envelope inner_r="13.0" outer_r="17.0" z_length="63 * 2"/>
<rphi_layout phi_tilt="0.0" nphi="12" phi0="0.2618" rc="15.05" dr="-1.15"/>
<z_layout dr="0.0" z0="0.0" nz="1"/>
</layer>
<layer module="VtxBarrelModuleOuter" id="2">
<barrel_envelope inner_r="21.0" outer_r="25.0" z_length="63 * 2"/>
<rphi_layout phi_tilt="0.0" nphi="12" phi0="0.2618" rc="23.03" dr="-1.13"/>
<layer module="VtxBarrelModuleOuter" id="3">
<barrel_envelope inner_r="34.0" outer_r="38.0" z_length="63 * 2"/>
<rphi_layout phi_tilt="0.0" nphi="18" phi0="0.0" rc="35.79" dr="-0.89"/>
<layer module="VtxBarrelModuleOuter" id="4">
<barrel_envelope inner_r="46.6" outer_r="50.6" z_length="63 * 2"/>
<rphi_layout phi_tilt="0.0" nphi="24" phi0="0.1309" rc="47.5" dr="0.81"/>
<layer module="VtxBarrelModuleOuter" id="5">
<barrel_envelope inner_r="59.0" outer_r="63.0" z_length="63 * 2"/>
<rphi_layout phi_tilt="0.0" nphi="30" phi0="0.0" rc="59.9" dr="0.77"/>
Maryland Physics Department Colloquium

41. The Barrel Vertex Detector
Maryland Physics Department Colloquium

42. LCIO SimTracker Hits from Vertex
CAD Drawing
GEANT Volumes
LCIO Hits
Maryland Physics Department Colloquium