Monte Carlo Truth in CMS Maya Stavrianakou FNALCMS

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Monte Carlo Truth in CMS Maya Stavrianakou FNAL/CMS 28. 09. 2005 M. Stavrianakou, FNAL

Monte Carlo Truth in CMS Maya Stavrianakou FNAL/CMS 28. 09. 2005 M. Stavrianakou, FNAL 1

The Current Scheme (I) £ Input event format ¤ CMS Raw. Hep. Event/Raw. Hep.

The Current Scheme (I) £ Input event format ¤ CMS Raw. Hep. Event/Raw. Hep. Event. Particle - HEPEVT-based £ Persistent collections ¤ Sim. Event: event ID, weight, collision vertex, generator particles, generated and simulated tracks (Sim. Track) and vertices (Sim. Vertex), additional generator info (e. g. Pythia parameters) ¤ Gen. Particle: PDG particle ID, generator status code, mother/daughter indices, momentum 4 -vector ¤ Sim. Track: PDG particle ID, momentum 4 -vector, vertex index and corresponding particle index in Gen. Particle container ¤ Sim. Vertex: vertex 4 -vector, parent particle index in Sim. Track container 28. 09. 2005 M. Stavrianakou, FNAL 2

The Current Scheme (II) £ MC truth selection ¤ all generator particles ¤ all

The Current Scheme (II) £ MC truth selection ¤ all generator particles ¤ all tracks produced in simulation if tagged for saving by subsystems (tracker, calo, muons) + track history pointing to last saved parent track ¤ all vertices for saved tracks, optionally “collapsed” ¤ mechanisms: Tracking. Action and Event. Action, where transient container of Tracks. With. History is filled and final selection and renumbering are made at the End. Of. Event action 28. 09. 2005 M. Stavrianakou, FNAL 3

Hep. MC-based scheme (I) £ Hep. MC: : Gen. Event format for generator input

Hep. MC-based scheme (I) £ Hep. MC: : Gen. Event format for generator input OK BUT need to pass and save additional parameters (int and double) such as ¤ Pythia process ID ¤ Numbers of participants, spectators etc and impact parameter for Heavy Ion studies Hep. MC: : Gen. Event wrapper? £ Hep. MC: : Gen. Event for final MC output? ¤ same consideration as for input ¤ wrt Hep. MC: : Gen. Particle need to ¥ Distinguish between original generator particles and additional G 4 simulation products ¥Distinguish between original decay vertex from generator and the one after G 4 particle tracking during decay proper time ¥Include additional info such as creator process ID etc Hep. MC: : Gen. Particle wrapper? 28. 09. 2005 M. Stavrianakou, FNAL 4

Hep. MC-based scheme (II) Possible implementation: CMSHep. MC: : Sim. Event modeled after Hep.

Hep. MC-based scheme (II) Possible implementation: CMSHep. MC: : Sim. Event modeled after Hep. MC: : Gen. Event with ¤ CMSHep. MC: : Sim. Particle ¥ a Hep. MC: : Gen. Particle wrapper with barcode to tag if original generator particle ¥ additional decay vertex info (Voriginal versus Vsimulated) ¥ other attributes (to be defined) additional generator parameters Use of Hep. MC could simplify track selection code CPU and memory improvements…. 28. 09. 2005 M. Stavrianakou, FNAL 5