# Presentation: 276649

## Simulating the Silicon Detector 

**Simulating the Silicon Detector**

**August 16, 2005**

**Norman Graf**
**SLAC**

## 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.

## LC Detector Full Simulation

- GEANT4

## GeomConverter

*GeomConverter*

- Compact
- Description

- LCDD

- HepRep

- org.lcsim
- Analysis &
- Reconstruction

- GODL

- Small Java program for converting from compact description to a variety of other formats

## lelaps

- Fast detector response package (Willy Langeveld).
- Handles decays in flight, multiple scattering and energy loss in trackers.
- Parameterizes shower development in calorimeters.
- Targets both sio and lcio at the hit level.
- Detector description runtime definable (godl)
- can be hand written
- can be exported from the compact description.

## Lelaps: Decays, dE/dx, MCS

-                Ξ0 → Λ π0
-                                 Λ → p π-
-                              π0 → γ γ as simulated by Lelaps for the LCD LD model.

*Lelaps: Decays, dE/dx, MCS*

- 	gamma conversion as simulated by Lelaps for the LCD LD model.

## SiDFeb05 Detector Envelopes

- Muon

- Coil

- Hcal

- trackers

- Ecal

-  **./sid/SiDEnvelope.lcdd**
-  *toy example* without real materials or layer structure
-  polyhedra for calorimeter envelopes
-  illustrates possibility of modeling realistic detector designs with “corners”
-  add trapezoid-shaped readout modules with box layers

## Vertex Detector

*Vertex Detector*

- 5 Layer CCD Barrel
- 4 Layer CCD Disks
- Be supports
- Foam Cryostat

-  <detectors>
-       <detector id="0" name="BarrelVertex" type="MultiLayerTracker" readout="VtxBarrHits">
-           <layer id="1" inner_r = "1.5*cm" outer_z = "6.25*cm">
-                 <slice material = "Silicon" width = "0.01*cm" sensitive = "yes" />
-           </layer>
-           <layer id="2" inner_r = "2.6*cm" outer_z = "6.25*cm">
-                 <slice material = "Silicon" width = "0.01*cm" sensitive = "yes" />
-           </layer>
-           <layer id="3" inner_r = "3.7*cm" outer_z = "6.25*cm">
-                 <slice material = "Silicon" width = "0.01*cm" sensitive = "yes" />
-           </layer>
-           <layer id="4" inner_r = "4.8*cm" outer_z = "6.25*cm" >
-                 <slice material = "Silicon" width = "0.01*cm" sensitive = "yes" />
-           </layer>
-           <layer id="5" inner_r = "6.0*cm" outer_z = "6.25*cm">
-                 <slice material = "Silicon" width = "0.01*cm" sensitive = "yes" />
-           </layer>
-      </detector>

## Central Tracking Detector

*Central Tracking Detector*

- 5 Layer Si -strips
- Barrel+Disk
- C-Rohacell-C supports

-   <detector id="2" name="BarrelTracker" type="MultiLayerTracker"  readout="TkrBarrHits">
-           <layer id="1" inner_r = "18.635*cm" outer_z = "26.67*cm">
-                 <slice material = "CarbonFiber" width = "0.025*cm" />
-                 <slice material = "Rohacell31" width="1.3*cm" />
-                 <slice material = "CarbonFiber" width=".025*cm" />
-                 <slice material = "Silicon" width = "0.03*cm" sensitive = "yes" />
-           </layer>
-           <layer id="2" inner_r = "44.885*cm" outer_z = "61.67*cm">
-                 <slice material = "CarbonFiber" width = "0.025*cm" />
-                 <slice material = "Rohacell31" width="1.3*cm" />
-                 <slice material = "CarbonFiber" width=".025*cm" />
-                 <slice material = "Silicon" width = "0.03*cm" sensitive = "yes" />
-           </layer>

## EM Calorimeter

*EM Calorimeter*

- W-Si Sampling
- Barrel+Endcap Disks

-  <detector id=“3" name="EMBarrel" type="CylindricalCalorimeter" readout="EcalBarrHits">
-          <dimensions inner_r = "127.0*cm" outer_z = "179.25*cm" />
-          <layer repeat=“30">
-            <slice material = "Tungsten" width = "0.25*cm" />
-            <slice material = "G10" width = "0.068*cm" />
-            <slice material = "Silicon" width = "0.032*cm" sensitive = "yes" />
-            <slice material = "Air" width = "0.025*cm" />
-          </layer>
-     </detector>

## Hadronic Calorimeter

*Hadronic Calorimeter*

- SS+RPC Sampling
- Barrel+Endcap Disks

-   <detector id="3" name="HADBarrel" type="CylindricalCalorimeter" readout="HcalBarrHits">
-          <dimensions inner_r = "138.5*cm" outer_z = "277.0*cm" />
-          <layer repeat=“34">
-            <slice material = “Stee1235" width = “2.0*cm" />
-            <slice material = "G10" width = "0.3*cm" />
-            <slice material = "PyrexGlass" width = "0.11*cm" />
-            <slice material = "RPCGas" width = "0.12*cm" sensitive = "yes" />
-            <slice material = "PyrexGlass" width = "0.11*cm" />
-            <slice material = "Air" width = "0.16*cm" />
-          </layer>
-     </detector>

## Muon System

*Muon System*

- Fe + RPC (Scint.)
- Barrel+Endcap Disks

-    <detector id="4" name="MuonBarrel" type="CylindricalCalorimeter"  readout="MuonBarrHits" >
-          <dimensions inner_r = "333.0*cm" outer_z = "277.0*cm" />
-          <layer repeat="48">
-            <slice material = "Iron" width = "5.0*cm" />
-            <slice material = "G10" width = "0.3*cm" />
-            <slice material = "PyrexGlass" width = "0.11*cm" />
-            <slice material = "RPCGas" width = "0.12*cm" sensitive = "yes" />
-            <slice material = "PyrexGlass" width = "0.11*cm" />
-            <slice material = "Air" width = "0.16*cm" />
-          </layer>
-     </detector>

## Far Forward Calorimetry

- W+Si Sampling, follows the layout of EM endcap.
- Needs to be refined, currently only a placeholder.

## MDI - BDS

- boolean solids

- polycones

- Both 2 and 20 milliradian solutions implemented.

- Machine Detector Interface and Beam Delivery System

## 2 and 20 milliradian

## Detector Variants

- XML format allows variations in detector geometries to be easily set up and studied:
- Stainless Steel vs. Tungsten HCal sampling material
- RPC vs. Scintillator readout
- Layering (radii, number, composition)
- Readout segmentation
- Tracking detector topologies
- “Wedding Cake” Nested Tracker vs. Barrel + Cap
- Field strength

## Detector Variants for Snowmass

- _[sidaug05](http://lcsim.org/detectors/index.html#sidaug05)_
- sidaug05_np
- _[sidaug05_4tesla](http://lcsim.org/detectors/index.html#sidaug05_4tesla)_
- _[sidaug05_scinthcal](http://lcsim.org/detectors/index.html#sidaug05_scinthcal)_
- cdcaug05
- cdcaug05_np
- cdcaug05_rpchcal
- cdcaug05_ecal150

## Slide 18

## Tracking Detector Readout

- Hits in Trackers record full MC information.
- Digitization is deferred to analysis stage.
- Nick Sinev has released a package to convert hits in silicon to CCD pixel hits.*
- MC Hits Pixels & PH Clusters Hits (x ± x)
- UCSC developed long-shaping-time -strip sim.*
- MC Hits Strips & PH Clusters Hits ( ± )
- Need short-strip simulation.
- Need tiling design for strip detectors.

*Tiling Forward Disks*

**Large Angle Stereo**

**Shallow Angle Stereo**

## Tracking

- Analytic covariance matrices available for fast MC smearing for each detector. Uses lcdtrk.
- Track “cheater” available for studies of full detector simulation events. Assigns hits on basis of MC parentage.
- Ab initio track finding and fitting code from hep.lcd being ported to org.lcsim.

## Calorimeter Reconstruction

- Sampling Fractions determined for each calorimeter and available at reconstruction time.
- derived from single particle response.
- remaining issues wrt digital/analog readout.
- Nearest-Neighbor and fixed-cone algorithms available in code distribution.
- Basic Cluster interface defined, can be extended.
- provides E, position centroid, direction, etc.
- EM shower shape 2 parameters defined, available at reconstruction time.

## Individual Particle Reconstruction

- Several groups are following different approaches towards individual particle reconstruction
- Identifying photons, electrons, charged & neutral hadron showers and muons.
- FastMC currently writes out LCIO files containing ReconstructedParticle objects.
- Aim to have the same for full reconstruction at the end of this workshop.
- Having physics analyses which use this data would be a great help in characterizing the detectors.

*Individual Particle Reconstruction*

- Z Pole event.
- Tracks and Clusters form ReconstructedParticles.
- Goal is 1:1 ReconstructedParticle  MCParticle

## “Standard LC MC Sample”

- Generate an inclusive set of MC events with all SM processes + backgrounds arising from beam- and brems-strahlung photons and machine-related particles.
- Used for realistic physics analyses and used by the  ILC physics community to represent a “standard” sample.
- Canonical background for Beyond-SM searches.
- Samples will be generated at several energy points to systematically study different ILC configurations.
- 500 GeV done.
- 350 GeV & 1 TeV in progress.
- 1 year’s worth of stdhep files fits on one external harddrive.

## Benchmark Data Samples

- Have generated canonical data samples and have processed them through full detector simulation.
- Single particles of various species: ~million events
- Z Pole events:   30k/detector, 240,000 events
- WW, ZZ, tt, qq, tau pairs, mu pairs, Z, Zh:
- 10-30k/detector, 960,000 events
- http://www.lcsim.org/datasets/ftp.html
- Also available here at Snowmass on USB/Firewire external drives.

## Reconstruction/Analysis Overview

- Java based reconstruction and analysis package
- Runs standalone or inside Java Analysis Studio (JAS)
- Fast MC  Smeared tracks and calorimeter clusters
- Full Event Reconstruction
- detector readout digitization (CCD pixels & Si -strips)*
*ab initio* track finding and fitting for ~arbitrary geometries*
- multiple calorimeter clustering algorithms
- Individual Particle reconstruction (cluster-track association)
- Analysis Tools (including WIRED event display)
- Physics Tools (Vertex Finding*, Jet Finding, Flavor Tagging*)
- Beam Background Overlays at detector hit level*
- Very aggressive program, strong desire to “do it right.”

## Reconstruction/Analysis

- Java Analysis Studio (JAS) provides a framework for event visualization (with WIRED) and reconstruction.

## Software CD

- We have developed a CD containing simulation and reconstruction software as well as documentation and tutorials. In addition, a small amount of data is available on this CD. (More on the Snowmass Data DVD.)
- Full Detector simulation is available through slic (GUI available for Windows).
- Fast Detector simulation is available through lelaps (Windows executable on CD).
- Reconstruction/analysis via org.lcsim & JAS.

## Computing Resources

- Your laptop!
- slic and lelaps executables available on the CD
- run your own events.
- SLAC Computing Services
- 300 batch slots available in dedicated queue
- thanks to BaBar.
- 4 TB disk space available for a short time
- thanks to GLAST.
- NICADD
- 50 processors with batch availability.

## Summary

- Framework exists for straightforwardly defining detector geometries.
- Digitization of tracker hits at analysis stage provides more degrees of freedom (pixel size, strip pitch, length, orientation, ...)
- Reconstruction & analysis framework is available, tuning and improvements welcomed.
- Data samples for several configurations available.
- This is your detector, help define it!

## Additional Information

- Linear Collider Simulations
- http://www.lcsim.org
- Silicon Detector Design Study
- http://www-sid.slac.stanford.edu/
- Discussion Forums
- http://forum.linearcollider.org