Physical Units Event Data Model Access to MonteCarlo truth DRAFT Brunel Conventions http://lhcb.cern.ch/computing/Reconstruction/Conventions/ Physical Units Event Data Model Access to MonteCarlo truth

Justification Conventions needed for: Request at last software week: Uniformity Maintainability Request at last software week: Proposals to come from Brunel manager Discussion period Until 10th September Approval Milano week Then mandatory for code accepted in Brunel First attempt If useful/successful, extend to other areas Not cast in stone: iterate after review

Physical Units All dimensioned quantities in the Gaudi data stores shall conform to the CLHEP system of units. All definitions of dimensioned quantities shall be dimensioned by multiplying by the units in CLHEP/Units/SystemOfUnits.h: const double my_height = 170*cm; // = 1700 const double my_weight = 75*kg; // = 4.68e+26 Output of dimensioned quantities converted to the required units by dividing by the units in CLHEP/Units/SystemOfUnits.h my_hist = histoSvc()->book( "/stat/diet", "corpulence (kg/m**2)", 30, 10., 40. ); double my_corpulence = my_weight / (my_height*my_height); my_hist->fill( my_corpulence/(kg/m2), 1. ); Physical constants should not be defined in LHCb code. They should be taken directly from CLHEP/Units/PhysicalConstants.h float my_rest_energy = my_weight * c_squared;

Event Data Model Glossary Naming convention MC Event: output of the event generator step. This typically includes MC Particles and MC Vertices MC Hits are the output of the GEANT tracking step. They typically include detector entrance and exit point, energy loss etc. FE data is the simulated output of the detector front end, as seen by the hardware triggers, when this is different from Raw data. Raw data is the output of the digitisation step of the detector simulation, and the output of the data acquisition system for real data. This typically consists of ADC and TDC counts. Coordinates are the output of the reconstruction program when applied to detector hits. This typically consists of hit coordinates, calorimeter clusters etc. Reconstructed data is the final output of the reconstruction program. This typically consists of tracks, particle ID, energy flow objects etc. Analysis data is the output of specialised analysis algorithms Naming convention MC classes that derive from a real data base class have the same name as the base class, prefixed by "MC” Need to agree on basic names. E.g. CaloDigit and OTDigi. We should converge on one. Digit seems more natural To be worked on!

Event Data Model Relationship between Raw data and MC Hits Implemented by inheritance

Event Data Model Generic relationship between reconstructed data and MC Hits Avoid need to read raw data to perform navigation TrTrack Attributes Operations MCParticle Attributes Operations 2..N 1 OTHit TrMeasurement Attributes Operations 1 2..N MCTrTrack MCHitList MCHitBase MCTrackingHit Attributes Operations 1 1 MCOTDigi OTDigi Attributes Operations

Access to MC truth Assume Gaudi associator tools can be implemented Gloria working on an example implementation Navigation between reconstructed data or digitisation output ("raw") data and MC truth must be done via associator tools. The reconstruction code must not assume any knowledge of how the navigation is implemented. In particular, objects in which the navigation is implemented by a MC derived class inheriting from a "real data" base class may be accessed by the reconstruction algorithms only via their "real data" base class. All comparisons with MC truth should be done inside dedicated monitor algorithms that are separate from the reconstruction/analysis algorithms. Monitor algorithms can also be used as a temporary measure to implement "cheating" algorithms in cases where the corresponding reconstruction algorithms have not yet been implemented