EicRoot for tracking R&D studies

Transcription

1 EicRoot for tracking R&D studies Alexander Kiselev EIC Software Meeting Jefferson Lab September,

2 Contents of the talk Tracking code implementation in EicRoot Few particular applications: Basic forward spectrometer Basic vertex+barrel tracker (with technical details) Complete model erhic detector tracker Summary 2/19

3 Tracking code implementation Large parts of other experiment s codes adapted: PandaRoot: ideal track finder, GenFit fitter, etc FopiRoot: TPC digitization, realistic track finders (Hough transform; Riemann sphere fit), GenFit fitter, RAVE vertex builder, etc HERMES: linearized Kalman filter for forward spectrometers Kalman filter fit quality for two extreme track configurations <ndf> = 206 <ndf> = 9 1 GeV/c π + tracks at η=0.5: 32 GeV/c π + tracks at η=3.0: 3/19

4 Feature list & restrictions Modularity and flexibility in geometry description Several detector templates available in digitization: Flat 1D (strip) and 2D (pixel) sensors; gaussian and sqrt(12) smearing Flat 2D {r,φ} sensors (endcap-like) Volume 3D (TPC-like) Volume 1+2D (axial symmetric along the track) Kalman filter fitting through all hits at once (via GenFit) No coding required rather than detector geometry description and steering macros (all in ROOT C++) 4/19

5 Feature list & restrictions Only ROOT TGeo geometry is supported Mapping information should be bundled in the same ROOT files with TGeo geometry description and it is directly available for digitization and reconstruction codes (so for each MC hit the information about physical volume it belongs to - shape, 3D transformation, etc - can be polled on-the-fly at any time) Ideal (known a-priori) hit-to-track association is typically assumed (suffices for resolution studies) 5/19

6 A remark about geometry description Respective radiation length scan erhic model detector vertex tracker element (TGeo geometry coded in C++) The prototype: ALICE ITS upgrade configuration How can one code such a thing in ASCII file by hand?! Otherwise: what sense does it make to have some custom intermediate format instead of coding in TGeo directly? 6/19

7 Example #1: basic forward tracker Which momentum resolution for 10 GeV/c pions will I get in ~3T field with 10 MAPS layers at η=3? Configurable geometry, material budget & resolutions Complete Kalman filter track fit -> see examples/tracking/config.1 directory for details 7/19

8 Example #2: basic vertex+barrel tracker Consider now vertex tracker + TPC in 3T field; shoot 10 GeV/c pions at θ=75 o -> see examples/tracking/config.2 directory for details 8/19

9 vtx-builder.c: objects (chips, staves) The only two sparsified placed (Unavoidable) geometry description overhead: trivial C++ coding this mapping structure will be appended to TGeo file 4 barrels at fixed radii; hardcoded number of staves TGeo stave volume TGeo chip volume stave assembly 9/19

10 vtx-builder.c: logical map initialization Create a unique entry for every elementary sensitive volume (silicon chips in this case) Keep this information as a single record in the same ROOT TGeo file Copy this record over as a whole into the file with simulated events (and thus make readily available for digitization and reconstruction) Couple all hits to their respective sensitive volume IDs (and all parent IDs) in the simulation 10/19

11 vtx-builder.c: composition, mapping, essential mapping entry creation call arrange 10-chip staves in 4 barrels assign color attributes using name patterns be paranoid if needed 11/19

12 simulation.c use GEANT3 transport engine add vertex detector add the TPC define particle kinematics define magnetic field 12/19

13 digitization.c digitize silicon as 20x40um pixels digitize TPC assuming 100um gaussian single point resolution in XY 13/19

14 reconstruction.c use silicon vertex detector hits use TPC hits perform Kalman filter track fitting perform back propagation to beam axis, etc 14/19

15 analysis.c open ROOT files; get TTree object define branches of interest loop through events and build plots 15/19

16 eventdisplay.c want to see tracks and hits 16/19

17 Example #3: EIC model detector tracker π + π + ; η=3 Same codes as for simple configurations Any sub-detector can be easily swapped in/out or replaced by the other one (see next slide) 17/19

18 erhic tracker alternatives TPC completely replaced by 6 layers of cylindrical micromegas No-structure GEM disks in the endcap TPC with reduced outer radius is just appended by few micromegas layers -> reconstruction codes will work the same way as before once respective ROOT steering scripts modified accordingly 18/19

19 Take away message EicRoot can be used as is for standalone R&D studies Several ready-to-go examples exist Codes available for download from BNL SVN server 19/19