North American Linear Collider Detector Simulations

1. Full Simulation flexible geometry specs within some constraints Gismo for simulation tool versatile output full MC record of digis platform support & MC Farms Use New Tools for Analysis using Root for simulation analysis and FastMC using JAS for all phases see Tony Johnson’s JAS talk Lessons learned LCD North American Linear Collider Detector Simulations CHEP 2000 Padova, Italy

2. LCD Road Map .lcd files stdHEP files .lcd files Root files Root files ASCII raw data ASCII recon Root Analysis Parameter Files (JAS) Geometry Description Files Parameter Files (Root) Gismo Material Files Generator Files Track Momentum Resolution Tables Generator(s) fastMC (Root) Gismo fastMC (JAS) JAS parser Root parser Root parser JAS parser Full Recon JAS analysis CHEP 2000 Padova, Italy

3. Reasonably full-featured full simulation package - C++ complex geometries EGS & GHEISHA cutoffs set at 1 MeV multiple scattering, dE/dx, etc Generator input from /HEPEVT/ via FNAL STDHEP I/O package Digitization supplied by ‘user’ tracking hit points at tracking/VXD layers calorimeters total energy per channel muon strips all digi’s have full MC record Output to ascii file (current) allows parsers to translate to JAS & Root for further analysis/processing ~ - ~ e+e-nn Gismo: Full Simulation CHEP 2000 Padova, Italy

4. Sample 5 GeV m+ CHEP 2000 Padova, Italy

5. Full Sim: Geometry Elements • Most detector types are cylinders • input by ascii detector file • trackers and calorimeters can have inner/outer skins and endplates • tracker/VXD layers can be individually positioned and sized • user sets longitudinal cell composition (multi-materials allowed) and ‘sensitivity’ for calorimeters • special shapes added in with parameters to describe their variations • conical masks configurable • compound beampipe CHEP 2000 Padova, Italy

6. Large (v. L1, L2) large! Large tracker optimal tracking resolution Large calorimeter optimal separation of clusters size limits B field may limit vertex detector inner radius due to e+e- pairs Small (v. S1, S2) small! Small detector larger B field possible Small calorimeter allows high granularity (Si/W) Small tracker Si strips/drift large B field better containment of pairs, closer-in vertex detector Two Detector Designs CHEP 2000 Padova, Italy

7. S1 L1 Pb-scint EM+HAD cal Coil Fe Muon Sys Cu-scint HAD cal W-Si EM cal Fe Muon Sys Coil 144 lyr TPC Pixel VXD 6-lyr Si drift Pixel VXD B=3T B=6T CHEP 2000 Padova, Italy

8. Small Detector: Central Detector • 3 Tracker Doublets • 1.1 mm G10, 600 mm Si • r = 14, 42, 71 cm • 5 EC Tracker disks • z = 31, 61, 91, 121, 149 cm • inner r follows cosq=0.99 • Luminosity monitor (Si/W) • active from 30-116 mrad CHEP 2000 Padova, Italy

9. Barrel/Endcap Region • <E> 15% lower than barrel • s/<E> 15% higher B/EC Small (note different scales on plots) Barrel CHEP 2000 Padova, Italy

10. Small EM Cal e+e- ZZ Si Tracker hits CHEP 2000 Padova, Italy

11. Large e+e- ZZ TPC hits EM Cal CHEP 2000 Padova, Italy

12. Tracking hit ID (x,y,z) of trajectory crossing layer layer DE ptr to MC parent hit smearing held off until recon Calorimeters hit ID (contains location) total energy deposited list of (MC parents, DE) MU Strips hit ID (contains location) list of MC parents Full MC Truth Table (x,y,z) at termination point initial (px, py, pz) type & charge pointer to parent position & momentum at Cal front face What You Get from FullSim CHEP 2000 Padova, Italy

13. LCD Event Class Structure Key: McPart Value: Energy EDeposit EM CAL Value: CalHit HAD CAL Value: CalHit MU CAL Value: CalHit MU Strips Value: stripHit LUM CAL Value: CalHit CAL Clusters Value: Cluster Value: McPart Track Value: Tracks Tracker Hits Value: Tracker_Hits VXD Hits Value: VXD_Hits MC Particles Value: McPart LUM Clusters Value: Cluster Event TObjArray Note: all hits, tracks & clusters have pointers back to parent MC. Clusters have pointers to constituent hits. CHEP 2000 Padova, Italy

14. MC Farms SLAC, Michigan, Colorado, Penn Code installed but yet to run production at Vanderbilt (DEC) & FNAL (Linux) data repository at Penn ‘push’ scripts for file transfer from farms server access via JAS ftp access for Root Timing ~2 mins/event for udscb 500 GeV on 400 MHz Solaris Platforms AIX Solaris DEC Unix Linux call stack corruption: compiler bug cannot optimize code Windows MC Farms & Platforms CHEP 2000 Padova, Italy

15. The Objective Provide an alternative to ASCII files which are by nature Information lossy Non dense Enforce data versioning Easily readable from C++ and Java Not Part Of The Objective A full object oriented serialization engine (a la Root or Objectivity) Provides Architecture independent binary format (uses the xdr standard) High integrity, self checking data layout Multiple simultaneously open input and output streams Heterogeneous record types on each stream Pointer relocation (at record level) Data compression/decompression (per record). Does not provide Abstract data descriptions Pointer chasing T.Waite Serial Input Output (SIO) CHEP 2000 Padova, Italy

16. For 1st pass LCD used ad hoc file format, one-of-a-kind code for serial-only parsing of detector geom. XML is a standard meta-language for defining markup languages. Good free parsers exist, more tools coming. XML languages are plain-text, self-documenting. Appl. interface to data (XML document) may be serial or random-access. Avoid growing private file formats or, worse, hard-coding parameters. Make it easy (well, easier) for several programs to use same input. J.Bogart Input: Why Use XML?

17. J.Bogart Detector Description in XML Start subdetector description <lcdparm> <global file=“largeParms2.xml” /> <physical_detector topology=“large” id = “L2” > <volume id=“EM_BARREL” > <tube> <barrel_dimensions inner_r = “196.0” outer_z = “322.0” /> <layering n=“40”> <slice material = “Pb” width = “0.4” /> <slice material = “Tyvek” width = “0.05” /> <slice material = “Polystyrene” width = “0.1” sensitive = “yes” /> </layering> <segmentation cos_theta = “300” phi = “300” /> </tube> <calorimeter type = “em” /> </volume> ... Geometry, materials function End subdectector description

18. Parser (XML4C) a good choice but multi-platform headaches. Java version also exists. Wrote a thin layer of utilities to provide more appropriate API. So far used by (but separate from) simulation only. Easy to port to Java. Benefits of standard format, pre-existing (free!) tools already apparent. Bigger, better utility layer Support for other forms of input, e.g. analysis cuts Evolving specs in the XML family (DOM Level 2, Schemas,...) bear watching. Other HEP (e.g. Atlas) and astrophysics (e.g. GLAST) experiments are doing similar things. Should coordinate efforts, aim for common XML DTDs/schema and supporting utilities. J.Bogart To come... So far...

19. 4000 Beamstrahlung particlesin the Small detector(A normal event will have 88,000/bunch x 95 bunches/train) G.Bower Beam Backgrounds Overlays • Background particles from Guinea Pig machine simulation • We plan to create a separate library of background events to overlay on top of the generator events. • Will have to apply cuts to the GP output to allow a reasonable particle count • large fraction don’t get to the beampipe because of the B field (by design!) • Then must overlay beam backgrounds, physics backgrounds and noise on top of true physics event (white lines are neutrals) CHEP 2000 Padova, Italy

20. In ‘96. Gismo was the only OO C++ simulation package on the market GEANT4 only available to public in past year Gismo does do full simulation with complex geometries so what’s the problem? Gismo has bugs/features that need fixing bug handling loopers MC particle chain not optimal for bremms no fluctuations on E loss and a few others Gismo support is down to one person in GLAST not so much interest in support as tool for HEP in general little or no documentation Future will need to include GEANT4 Gismo? CHEP 2000 Padova, Italy

21. e+e- detectors look pretty similar (except RICH!) not hard to define user interface (ascii file) to describe important features specialty items can be added as designs start to focus on details XML does the job nicely Flexible I/O needed must be easy to read from different analysis interfaces (eg C++, Java) ascii is bad for numeric precision ended up with xdr-based binary I/O Provide Full MC parentage for understanding algorithms Gismo sufficed for startup of project prior to G4, but should switch Hard to fully support more than one framework tried to support JAS and Root could not share code between them had to write everything twice was divisive should have (and will) support one fully and the other only as able to take output from the other. Lessons Learned CHEP 2000 Padova, Italy