1. Norman Graf SiD Workshop, Eugene November 15, 2010
SiD Simulation
Norman Graf
SiD Workshop, Eugene
November 15, 2010

2. Work Plan for 2012
1. Demonstrate proof of principle on critical components. 2. Define a feasible baseline design. 3. Complete basic mechanical integration of the baseline design… 4. Develop a realistic simulation model of the baseline design, including the identified faults and limitations. 5. Develop a push-pull mechanism, … 6. Develop a realistic concept of integration with the accelerator … 7. Simulate and analyze updated benchmark reactions with the realistic detector model. Include the impact of detector dead zones and updated background conditions. 8. Simulate and study some reactions at 1 TeV, including realistic higher energy backgrounds, demonstrating the detector performance. For 7 and 8, Specific physics channels will be investigated and defined by the Physics Common Task Group and supported by the Software Common Task Group. 9. Develop an improved cost estimate.

3. Beyond the LOI
The detector model sid02 was a necessary compromise between the desire to include all the details of the engineering designs and the need to complete the large-scale physics benchmarking simulations in a timely fashion.
Since then have developed a detector model which includes more realistic detectors.
Benefits from engineering work done for the LOI.
Allows much more realistic subdetector performance studies to be undertaken.

4. Calorimeter Model with Gaps
gaps between calorimeter staves
material can be specified
parameters to compact
modeled with one volume inside another
layering in daughter volume

5. Non-Projective Stave HCal Model
work in progress
not ready for simulation yet
need some additional infrastructure to support this geometry (boolean volumes, layering)

6. Pointing vs Non-pointing HCal
Projective advantages:
All modules are the same (+ smaller largest module)
Pseudo-layer reconstruction (e.g. pandora) possible
Consistent depth in phi
Non-projective advantages:
Inter-module cracks do not point to origin
Current strategy is to pursue symmetric Hcal and only implement other model if needed.
Current studies show minimal, if any, effect of cracks on PFA performance.
Number of cracks reduced with octagonal layout.

7. 0, 5 and 10mm steel skins in HCal Barrel
Using single u jets of 50GeV,
differences between HCal
modules is not statistically
significant.
Further studies are ongoing.
No strong motivation to pursue
non-pointing stave geometry.

8. Improving RPC response simulations
Characterize average multiplicity using current standalone simulation.
Custom Geant4 program writes out individual hits from a shower in the RPC gas-gap.
Processed using a FORTRAN program to calculate the charge spreading and populate the neighboring cells if the charge spreads beyond a cell boundary.
Use DigiSim to incorporate this average cross-talk on a statistical basis and see whether the final results change. I
If not, we can use this approach for physics analyses
If there are significant differences, can the charge spreading be parameterized to provide a simple formula for the number of hit neighbors as a function of the distance between the MC energy deposition to the cell edge?
This could then, with some work, be incorporated into the slic simulations.
If not, and we need to account for a number of small depositions adding up to exceed some threshold, determine a fiducial region in the center of the cell for which no neighbors will be created.
Modify slic to only write out the individual hit information in the border regions.
Provide a C++ or java version of the FORTRAN code to incorporate into either slic or lcsim.

9. RPC simulation overview
Had ‘Edep’ within
D0 before?
Geant4 find
a ‘Edep’ in RPC
Yes
No charge!
continue No
Generate total charge
according to C-spectrum
Distribute on pads
according to measured
distribution No
DHCal
hits
End of evt?
Yes
Apply
threshold
Fortran program (by Jose Repond) exists since a long time ago
Re-written recently (L. Xia) in order to be included in SiD simulation
Program speed is also significantly improved
Lei Xia

10. Total charge generation
Measured charge distribution
for HV = 6.2 kV
Before re-writing
After re-writing
Generated charge
by randomly throwing points
Using look-up table
Slightly faster
Lei Xia

11. Charge distribution on pads (I)
Measured charge distribution as
function of y in the pick-up plane
D.Underwood et al.
Before re-writing
After re-writing
Throw 10,000 points in
x,y plane, calculate charge Q(r),
sum up charge on 1 x 1 cm2 pads
Using look-up table, much faster
Better accuracy
Distribute charge on 3x3 pads
Ignore charge outside 3x3
This part of the new algorithm
still need to be verified by old
program
Lei Xia

12. Charge distribution on pads (II)
Total charge [pC] outside
3x3 pads: < 1%
Charge distribution [pC] on 3x3 pads
(6.3kV, Edep randomly generated on central pad)
N(hit) distribution (thr = 0.6pC)
Efficiency ~ 89%
Multiplicity ~ 1.33
Lei Xia

13. Next step Verify whole algorithm with old program
Very soon
Verify using standalone Geant4 simulation
Integrate into SiD simulation
Should not be difficult, can be soon
Lei Xia

14. Tracking Geometry LOI geometry consisted of cylinders and disks
New geometry models each silicon sensor – rectangular detectors in barrel, trapezoidal detectors in endcaps, with module overlap in r,  and z, including dished endcaps.

15. Detector Optimization
MIT group engaged in systematic study of HCal variants based on simplified SiD geometries using slic + SiD PFA (talk by R. Cowan).
extending studies done for the LOI by Marcel Stanitzki using Mokka + MarlinReco (SiD-ish)
primarily studying HCal depth and layout.
Should we engage in a similar global exercise?
Tracker layouts
Detector aspect ratios
Ecal design
HCal absorber materials, layout, readout technologies.

16. Optimization Designs
Defined a series of detectors designed to easily and efficiently optimize the HCal design (currently the critical path item).
Simulate very deep HCal barrel and endcap
60 and 70 layers deep
Analyze resolution as a function of the number of layers used in reconstruction.
Generate variants to study absorber material, readout technology and dead material in cracks.

17. Scintillator (analog)
sidloi_opt variants
RPC (digital)
sidloi_opt
sidloi_opt_5mmskin
sidloi_opt_octagonal
sidloi_opt_w
Scintillator (analog)
sidloi_opt_scint
sidloi_opt_scint_5mmskin
sidloi_opt_scint_octagonal
sidloi_opt_w_scint

18. Optimization Tools
Code has been written to automate standard procedures needed for new detectors:
Sampling Fraction determination
MIP most-probable-value determination
EM shower sampling fractions for Ecal, Hcal, Barrel, Endcap
Had shower sampling fractions for Ecal, Hcal, Barrel, Endcap
EM shower covariance matrices for particle ID
Standard energy and position resolution plot generation.

19. Optimization Data Sets
Single , , K0L, at fixed angles and energies for sampling fraction determination.
Single particles (as above, plus e,  ,K ,p,…) at variable angles and energies to study clustering and tracking efficiency and resolution.
Simple resonances (0,,) to study efficiency and resolution of two-particle states.
Single quarks at fixed energies to study jet energy resolution (u,d,s).
Single Z0 at fixed energies to study dijet mass resolution.

20. Diagnostic Plots /E vs 1/E Cluster Energy MC Energy vs Cluster E
Residuals vs E
/E vs E

21. Single Photon Response (Barrel)
single photons of discrete energies
1,2,5,10,20,50 &100 GeV
theta=90 degrees
phi=0 degrees
misses overlapping portion of barrel staves in EM calorimeter

22. Single Photon Linearity (Barrel)
slope:
intercept:

23. Single Photon Residuals (Barrel)
Full range ~2%
But systematic trend obvious.

24. Single Photon Resolution (Barrel)

25. Single Photon Resolution (Barrel)
slope:
intercept: 0.005

26. Single K0L Response (Barrel)
single K0L of discrete energies
1,2,5,10,20,50 &100 GeV
theta=90 degrees
phi=0 degrees
misses projective cracks of barrel modules in Had calorimeter

27. Single K0L Linearity (Barrel)
slope:
intercept:

28. Single K0L Residuals (Barrel)

29. Single K0L Resolution (Barrel)

30. Single K0L Resolution (Barrel)
slope:
intercept:

31. SiD Optimizations ECal resolution could be improved with thicker Si
ECal thickness (cost) could be reduced
ECal/Hcal separation is somewhat artificial
Excellent high energy , e+/- response with analog HCal
Octagonal Barrel geometry
reduces number of phi “cracks”
reduces amount of overlap in EM staves
Is Tracker layout Optimal?
Pixel Tracker option very attractive …

33. Silicon Detector Definition
Expect that the detector design will change going forward.
Need to implement some form of Change Control Board to ensure that the modifications motivated by physics studies or engineering constraints are formally communicated to the subdetector, simulation and reconstruction groups.

34. lcsim Reconstruction
Tracking reconstruction now features planar silicon wafers, full hit digitization, clustering to form hits (with hit-size dependent uncertainties) and ab initio track-finding (talk by R. Partridge).
Calorimeter code has been modified to support polygonal modules and PFA adapted to the new geometries(talk by R. Cassell).
PFA code is being improved (talks by U. Mallik & R. Zaidan).
Reconstruction is run-time configurable.
Allows new users to begin running reconstruction without having to code Drivers, etc.

35. Clustering across modules
Efficiency of cross module
clustering.
geometry
Particle ID efficiency as a
function of phi.
shower shape
Energy resolution as a
sampling fractions
Thin absorber
Thick
absorber
+/- 1%
100 GeV photons
Phi
Energy

36. 0,  / 0 Tests charged / neutral clustering
in locally dense environment.
Resonance mass is performance metric.

37. Jets
Single quarks (u,d,s) at fixed energies and angles. Tests energy resolution in controlled environment.

38. Z0qq
Single boson decaying to light quarks at fixed energies and angles. Tests invariant mass resolution as function of boson energy.

39. slicPandora Developed to support the CLIC SiD’ studies
using analog scntillator readout
Not a replacement for SiD PFA
using digital RPC readout
Full chain of analysis demonstrated
generation of geometry description
generation of track-states & calorimeter hit input
including all relevant sampling fractions
PFO creation and analysis
overall energy scale to be determined
See talks by J. McCormick (infrastructure) and P. Speckmeyer (use at CLIC).

40. Track Finding No significant changes to LOI track finding algorithm.
Some structural/implementation changes to improve tracking performance, especially with large numbers of hits.
A couple of known issues are being worked on:
Forward efficiency is worse than LOI – fast checking of hit pairs, misplaced digitized hits.
Events have been found where tracking takes a very long time.
overlapping modules in barrel regions  4 hits / layer.
Hits in multiple wafers in same layer can create ghost tracks. (see above)
See talk by R. Partridge for details.

41. Tracking: Future Work Further optimization of the detector layout
Number and position of layers
Strip and pixel size and layout
All pixel tracker option
Additional studies of calorimeter assisted tracking
Assist in kink finding and identification
Identification of long-lived resonance decays &  conversions
Systematic studies of the impact of:
hit inefficiencies / dead channels,
non-uniform magnetic field,
beam backgrounds, …

42. Computing Resources
LOI made extensive use of both the LCG and OSG grids.
LCG: DESY, RAL Tier 1, in2p3, …
OSG running opportunistically on the CMS FNAL
In general, no problems with the concept software
SiD software (slic & org.lcsim) just worked (also ran MarlinReco on LCG where it was installed).
This process can no longer rely on individuals, it has to be institutionalized, automated and coordinated with ILD & CLIC within the ILC VO.
See next talk by J. McCormick on Dirac.
Not clear what, if any, resources remain available at SLAC.

43. Summary Simulation infrastructure essentially done.
Reconstruction code being adapted for more complex geometries, (PFA & tracking).
Workflow being streamlined & automated.
Detector optimization studies being conducted before major event production.
First set of detectors defined, and large set of diagnostic events available for analysis.
Would like to see some physics benchmarks used
CLIC CDR is “pilot” job.
see talk by P. Speckmeyer)