Linear Collider Detector Simulations at SLAC

1. Linear Collider Detector Simulations at SLAC R. Cassell, J. McCormick (presented by N. Graf) ALCPG Victoria Meeting July 28, 2004

2. MC Event G4Application Geometry Geometry Database Reconstruction, Visualization, … LC Detector Full Simulation Simulated Response GEANT4

3. G4Applications • G4 kernel handles physics, major problems are which particles to store, keeping the complete parentage, associating hits with the correct stored particle and formatting I/O. • LCDRoot provides ROOT-based interface. • Toshi Abe (SLAC) • lcdg4 provides sio output • Guilherme Lima (NIU) • lcs provides lcio output • Ron Cassell (SLAC)

4. LCS - Components • Event Input – Binary STDHEP files Borrowed two classes from LELAPS to read the binary files. (lStdHep and lXDR) Wrote LCSHepEvtInterface to sort out the sometimes inconsistent parentage information. • Physics Lists – Prepackaged Lists from G4 Can choose from various models at runtime, e.g. LHEP, QGSP, QGSP_BERT, … • Geometry – XML Input Files Borrowed and modified lcdg4 code for reading xml file and creating G4 geometry.

5. LCS - Components • Event Output – LCIO format Uses head version of LCIO (tagged as forLCS). Creates LCWriter in main. Creates Run header in LCSRunAction. Creates all Event Classes in LCSEventAction. (Isolate as much as possible from main body of G4) Attempts to implement all LCIO output options with flags. (The value of the flags is currently hardwired, will be changed soon) See LCIO documentation for a complete description of the format at: http://lcio.desy.de/

6. LCS – A few details • Tracking Region: Using the G4 Region mechanism, a tracking region is defined. Currently the tracking region is defined as a cylinder with R=maximum R of all trackers, Z= +-maximum Z of all trackers. • Storing (and writing) particles: All particles input by the generator (including strings, quarks, gluons etc) are stored with the correct (multiple) parentage. Particles created in the simulator:: Define a shower particle as any particle created in a non-tracking region, or the daughter of a shower particle.

7. Storing (and writing) particles (cont) Shower particles are only stored if they produce a tracker hit, as the daughter of the non-shower particle producing the shower, with the backscatter status set. Non-shower particles are stored, if KE > (user threshold) or if producing a tracker hit. • Hit Assignments Tracker hits are assigned to the particle that produced them. (Warning, neutrals can produce tracker hits in G4) Calorimeter hits are assigned to the particle producing the shower.

8. Psi->hadrons: Wired event display

9. Wired Event Display: ttbar event

10. Sanity check: LCDG4 comparisons • For comparison, generate 1000 events each of 500GeV qq, tt, WW, ZZ, and ZH140 in SDJan03 detector with lcdg4 and lcs • Generator and Simulator final state energy • Number of hits, energy per hit, and energy per event for sub-detectors. • Parallel analyses of sio and lcio output. • Comparisons exposed features which were subsequently fixed.

11. Code Availability • There is a LCS web page at: http://www.lcsim.org/simulation/lcs/index.html It contains instructions for checking out the code from CVS, as well as a pointer to the documentation.

12. Data Sets: available through server with anonymous ftp at: ftp://ftp-lcd.slac.stanford.edu/lcd/NewData/ Physics Events – 1000 events each of e+e- -> X at 500GeV. X = qqbar, ttbar, ZZ, ZH120, W W 1000 events ZPoleHadronic Single Particle Diagnostic Events – 1000 event samples: Particle Decay Theta range Energy (GeV) pi0 90 .5, 1, 2, 5, 10, 20 gamma 90 .5, 1. 2. 5. 10. 20 neutron 90 1-10 muon 4-176 1-10 pions 4-176 1-10 Kshort pi+pi-,pi0pi0 45-135 5-25 pho+ pi+pi0,pi+gamma 90 10 tau 3pi, 5pi 20-90 10-200 psi hadrons 20-160 5-100 psi mumu displaced vertex Data Availability

13. Updated Geometry Specification • For flexibility and ease of construction, subdetector geometries have been based on simplified geometries, e.g. cylindrical barrels and disks. • Have recently developed a set of geometry definition classes to handle more realistic geometries • parametric definitions of polygonal barrels and disks. • Introduced parametric slicing.

14. Updated Geometries • Can define n-sided detectors. • user-defined slicing of stave modules • Developing xml schema for geometries.

15. Slicing • Arbitrary slicing of subdetector staves • Example SiD Si/W EM calorimeter.

16. Digitization • Currently working on definitions of “generic” sensitive detector readout digitization for calorimeter detectors. • projective or non-projective • “natural” coordinate binning, e.g. • Cylinder • either  (projective) or z (fixed cell size) • Disk • either r (projective) or xy (fixed cell size) • Box • partition along u,v axeS

17. Summary • LCS is a working (though far from polished) Geant4 simulation package implementing the LCIO simulation data model. • Actively developing improved detector geometries. • Parameterized polygons with arbitrary slicing. • Planning arbitrary placements of any G4 volumes. • Digitization being decoupled, abstracted. • Close collaboration with SLAC Geant4 experts is crucial and much appreciated.