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Detector Description of LHCb Detector

Detector Description of LHCb Detector. On behalf of the Simulation and Database Teams. S.Easo 24-5-2013. Detector Description. Contains our knowledge of the detector , that is used in simulation, digitization and reconstructon. What is possible now:.

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Detector Description of LHCb Detector

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  1. Detector Description of LHCb Detector On behalf of the Simulation and Database Teams S.Easo 24-5-2013

  2. Detector Description • Contains our knowledge of the detector , that is used in simulation, digitization and • reconstructon. • What is possible now: • Create some basic shapes and material composition of detector parts. • Combine basic shapes with boolean operations • Apply Detector Conditions ( example: pressure, temperature ) • Apply misalignment for simulation, alignment for reconstruction • Readout configurations (mainly for digitization and reconstruction) • Visualize the detector in different graphics programs • Desirable features: A: Improvement in the way • Interface to Geant4 is used • misalignment can be applied for simulation • Material scan at different Z locations is performed B: Improvement in the detector description to match up with results from real data C: Improved support for Geant4 graphics D: Smoother procedures for validation before release E: Managing the evolutions of ‘upgrade’ and ‘current’ LHCb descriptions

  3. GiGa Service Persistency Service Geant4 Transient Detector Store GiGa Geometry Conversion Service condition DB geo DB LHCb geometry in simulation Gauss converts the LHCb geometry to the Geant4 description: Converters and Service GiGaGeo G4 geometry “Geo” (Gaudi Algorithm) list of detectors (trees) to convert Geo.StreamItems += {"/dd/Structure/LHCb/BeforeMagnetRegion/Velo"}; Geo.StreamItems += {"/dd/Structure/LHCb/BeforeMagnetRegion/Rich1"}; Geo.StreamItems += {"/dd/Geometry/BeforeMagnetRegion/Rich1/Rich1Surfaces"}; ... This list is in Gauss configurable

  4. Applying misalignment in simulation A= HPD B=Si Anode inside HPD lvA3, pvA3, deA3 lvA2, pvA2, deA2 lvA1, pvA1, deA1 l l l (a) Misalignment works OK for ‘B’ lvB3, pvB3, deB3 lvB2, pvB2, deB2 lvB1, pvB1,deB1 lvA, pvA3, deA3 lvA, pvA2, deA2 lvA, pvA1, deA1 l l l Misalignment does not work for ‘B’ (b) lvB, pvB, deB3 lvB, pvB,deB1 lvB, pvB, deB2 • Minor incompatibility between the concepts of ‘lv/pv ‘ and ‘de ‘ in LHCb • Misalignment info created for the list of ‘de’ for A and B. • But G4 fills info for each ‘pv’ and tries to find the corresponding ‘de’ to get the info. • Needs a unique ‘lv/pv’ path names. • If one uses the scheme (b) and would like to apply misalignment, • it would require some changesin GiGaCnv.

  5. Material budget Scan • Find the tracks incident in various ‘Z’ planes • and evaluate the material seen by Geant4. • In some cases it is difficult to find an Z plane and one risks overlaps if • we insert new planes just for this. • Possibility to interface to the ‘parallel world’ in Geant4 whereby • one can create these planes without risk of overlaps. • Needs to add the necessary interface in GiGa for this. Also set the • attributes in the geometry description so that these are ignored during • reconstruction. • A recent study started to evaluate these budget scans

  6. Simulation vs Real data • Number of tracks and hits in real data are more than what is in MC. • Needs to verify if this is from ‘not tracking’ the low energy secondary • particles or due to pythia/Evtgenmodelling or • from ‘lack of material’ in the detector description. • If this is due to ‘lack of material’ , one would need to fix this in the database. • There have been some studies towards this, but no definitive conclusions ? • Recently a new study started to investigate this problem for RICH (From physics analysis talk 21-5-13 by F.Soomro) Not the latest version of MC

  7. Graphics Panoramix: GEANT4 Visualization: (a) Visualize geometry directly (b) Visualize reconstructed information Normally geometry is loaded at the initialization level • Use OpenGL, DAWN etc to see the detector geometry. • OpenGL , in principle allows interactive visualization. • These can be activated from Gauss • In principle, possible to see the tracks created by Geant4 • Difficult to step through the events • due to issues with ‘event loop’ ownership • These capabilities are quite useful for upgrade studies

  8. Graphics DAWN: Creates .prim files which can be seen by DAWN GUI interface or by DAVID DAVID can detect geometry overlaps and convert them to a graphics for easy visualization. ASCITree dumps the geometry hierarchy as a text tree https://twiki.cern.ch/twiki/bin/view/LHCb/FAQ/GaussVisualization

  9. Overlap testing • Overlaps are NOT good in GEANT4 • Particle can get stuck • Event can abort • Produce Unexpected results • Possible crashes • To test overlaps: • DetDescCheck in LHCb • DAVID in GEANT4 • Other Geant4 tools • Lot of the ‘overlaps’ can be just machine precision issues.

  10. Geometry Databases Current LHCb : Geometry described in DDDB Detector conditions in SIMCOND for simulation LHCbCOND for real data Different ‘datatypes’ to distinguish between the geometries used in different years (2011, 2012 etc ). Detector conditions evolve over the years (Alignment, calibration etc) Occasional modifications in the geometry (DDDB) Upgrade LHCb : A separate database with the structure for DDDB and SIMCOND similar to that for ‘Current LHCb’ Contains different geometry options for sub detectors Various ‘datatypes’ (and local tags) to activate different detector options. (examples: VP/VL, IT+OT / FT ) Various changes to geometry Database (DDDB) these months. Starting have some modifications in SIMCOND. For now, both Current and Upgrade databases need to be maintained continuously

  11. Use of Database in the coming months • Simulation of the backgrounds: Addition of materials (infrastructure for example) • outside the acceptance • Validation of database: • Some tests for overlaps exist. (Graphics, DetDescChecks, G4 tests etc). • A few QM tests exist to validate new detector geometry in applications • May need to think of more tests and convert them to QM tests • to ensure a smooth release process Upgrade: • Few more detector options are envisaged (No SPD/PRS, new RICH etc ). • Once the major detector choices are made, we may reduce the number of • combinations of the detector geometry options that are to be maintained. • Velo RF Foil : GDML description to run Gauss being tested in private studies, • Need investigation to see if CPU time is prohibitive.

  12. How to use Simulation Various twiki pages exist on how to use the Simulation: https://twiki.cern.ch/twiki/bin/view/LHCb/LHCbSimulation https://twiki.cern.ch/twiki/bin/view/LHCb/SimulationUpgrade https://twiki.cern.ch/twiki/bin/view/LHCb/GeometryActivationExamples Feed back welcome

  13. Summary • We have working versions of the Geometry setups for current and upgrade • There are improvements which are desirable: • Smoother graphics usage • More comparisons with real data to see if it gives same results • Interface to ‘parallel world’ • More QM tests

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