1. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 0 WP 1 – Simulation and Physics Studies LCFI Oversight Committee Meeting, 12 th July 2006 Sonja Hillert on behalf of the LCFI collaboration

2. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 1  current focus: work towards completion of C++ based Vertex Package comprising vertex finder ZVTOP, NN-based flavour tag and quark charge sign selection  fast MC SGV provides good basis for testing the new software : results for performance obtained with FORTRAN version available for cross-checks detailed comparison of different versions possible by using identical input events  C++ based code should perform at least as well as FORTRAN version; improvements of code wrt FORTRAN will be guided by comparison with MC information  for more complex branch of ZVTOP this goal has already been reached; other parts of the vertex package are far advanced and converging well  in parallel : performance comparison of different detector designs using fast MC SGV preparation for study of sensitive physics channels Introduction

3. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 2 interface SGV to internal format interface LCIO to internal format input to LCFI Vertex Package output of LCFI Vertex Package interface internal format to SGV interface internal format to LCIO ZVRESZVKIN ZVTOP: vertex information track attachment assuming c jet track attachment assuming b jet track attachment for flavour tag find vertex- dependent flavour tag inputs find vertex charge find vertex- independent flavour tag inputs neural net flavour tag

4. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 3 Work since last OsC meeting and current status  coding, debugging / validation and documentation progressing in parallel  validation has focused on ZVRES branch: detailed tests of increasing complexity (Ben Jeffery) checks at the 1-2 track level with simplified conditions allowed thorough debugging of the track swimming and vertex fitting algorithms current version shows excellent agreement with FORTRAN – C++ performing slightly better system test in conjunction with flavour tag and vertex charge reconstruction beginning  ZVKIN: first part (finding ghost track) coded, initial tests promising  have recently taken up work on: designing coherent class structure for entire package calculating flavour tag inputs (Erik Devetak) embedding the existing NN software into our package (Mark Grimes)  profiting from contact with ILC software experts on interfacing issues

5. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 4 Comparison of C++ & FORTRAN ZVRES  compare distributions of number of vertices and of tracks per vertex between C++, FORTRAN and MC truth for 100 GeV b-jets  excellent agreement between the results from C++ and from FORTRAN Ben Jeffery

6. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 5 Comparison of track-vertex association  tables show percentages of tracks from the primary, B- and D-hadron decay at MC level that are assigned to primary, secondary (and tertiary) vertex or left isolated by ZVRES;  excellent agreement also seen in this detailed comparison of the two versions  results above were obtained for 100 GeV b-jets; corresponding studies at 25 GeV and 250 GeV jet energy show equally good agreement Mark Grimes

7. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 6 54% negative (C++ version better) Ben Jeffery Performance of decay length reconstruction difference between the C++ and the FORTRAN deviation from MC in decay length right: distribution of this difference, left: difference plotted vs MC decay length fitter yields different vertex position differences in track- vertex associations C++ finds some vertices FORTRAN misses and comes closer to MC truth than FORTRAN for entire range of decay lengths

8. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 7 E CM = 100 GeV b c (b-bkgr) c open: FORTRAN full: C++ First full test of C++ ZVRES in FORTRAN framework  compare FORTRAN to C++ ZVRES when fed with identical input events  unrealistically large fixed track errors used in both versions for diagnostic purposes  identical FORTRAN code for flavour tag (left) and vertex charge (right)  flavour tag: good agreement between C++ and FORTRAN, with C++ slightly better for b-jets  for vertex charge C++ in this first test performs considerably less well than FORTRAN – but could be more sensitive to fixed huge track errors Sonja Hillert

9. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 8 Interfacing the Vertex Package  Use LCIO persistency framework for Vertex Package input & output  Package will be interfaced to MarlinReco reconstruction framework, based on Marlin (Modular Analysis & Reconstruction for the LINear collider) software modules called processors, each has set of input parameters, order of processors is defined via XML steering file  easy to exchange modules without recompiling, can run the same processor with different parameter set in one job  will provide processors giving example code for running ZVTOP (one processor for each of the two branches ZVRES, ZVKIN) calculating neural net input variables from input to package & ZVTOP output training neural nets for flavour tag, obtaining NN outputs for pre-trained nets, vertex charge calculation combined processor: ZVRES + Hawkings flavour tag + vertex charge calculation

10. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 9 Sensitivity to other parameters  since vertex charge performance is sensitive to multiple scattering need to keep layer thickness small (target 0.1 % X 0 )  also strong dependence on momentum cut (track selection) – this depends critically on tracking performance: track finding capability background rates linking across subdetector boundaries  should push all these parameters to their limits, as all these effects will eventually add up in the real detector

11. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 10 Future plans beyond the Vertex Package release  more detailed comparisons with performance obtained when using MarlinReco – in particular, compare results from ‘cheaters’ to full track reconstruction, for which algorithms independent of the old BRAHMS code, are now under development  performance of our tools with different choices for the input can provide useful feedback for tracking code development important for us: step towards full framework, ensure we understand later physics results  explore and quantify what can be gained for flavour tag and vertex charge when using the ghost track (ZVKIN) algorithm should feed into future update, so the community can profit from our studies  begin study of benchmark physics processes: e + e -  b bbar with extra dimensions model as studied by Riemann, Hewett SUSY physics further physics processes

12. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 11 Summary and outlook  Development and validation of the LCFI Vertex Package are far advanced.  Excellent agreement is found between C++ and FORTRAN ZVRES branch of ZVTOP.  A structure for the internal working classes and the interface to LCIO / MarlinReco is under development; LCIO will be modified to accommodate output of our package.  Code for calculating flavour tag inputs is being written and tested; the interface of the NN software for the flavour tag is being developed in parallel.  Vertex charge reconstruction for c-jets is under study (Victoria Martin).  Using optimistic time estimates, release end of September should be possible.  Detailed comparisons with MarlinReco input and quantitative exploration of improvements from the ghost track algorithm will be next steps after the release, in parallel to first studies of benchmarks processes sensitive to the detector design.

13. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 12 Additional Material

14. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 13 ZVTOP - Progress Initial aim: replace FORTRAN ZVRES in SGV for testing - allows comparison of intermediate algorithm states when working on identical tracks - new version can be verified to be at least as good as FORTRAN SGVFORTRAN ZVRESFlavour Tag tracks vertices SGV FORTRAN ZVRES Flavour Tag C++ ZVRES Current Status Add ZVKIN: SGV C++ ZVRES Flavour Tag C++ ZVKIN LCIOC++ ZVTOP LCIO Finally:

15. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 14 The ZVTOP vertex finder two branches: ZVRES and ZVKIN (also known as ghost track algorithm) The ZVRES algorithm:  tracks approximated as Gaussian ´probability tubes´  from these, a ´vertex function´ is obtained:  3D-space searched for maxima in the vertex function that satisfy resolubility criterion; track can be contained in > 1 candidate vertex  iterative cuts on  2 of vertex fit and maximisation of vertex function results in unambiguous assignment of tracks to vertices  has been shown to work in various environments differing in energy range, detectors used and physics extracted  very general algorithm that can cope with arbitrary multi-prong decay topologies D. Jackson, NIM A 388 (1997) 247

16. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 15 The ZVKIN (ghost track) algorithm  more specialised algorithm to extend coverage to b-jets in which one or both secondary and tertiary vertex are 1-pronged and / or in which the B is very short-lived;  algorithm relies on the fact that IP, B- and D-decay vertex lie on an approximately straight line due to the boost of the B hadron  should improve flavour tagging capabilities ZVRES GHOST SLD VXD3 bb-MC

17. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 16 tanh (M Pt / 5 GeV) joint probability uds c b Flavour tag  Vertex package will provide flavour tag procedure developed by R. Hawkings et al (LC-PHSM-2000-021) and recently used by K. Desch / Th. Kuhl as default  NN-input variables used: if secondary vertex found: M Pt, momentum of secondary vertex, and its decay length and decay length significance if only primary vertex found: momentum and impact parameter significance in R-  and z for the two most-significant tracks in the jet in both cases: joint probability in R-  and z (estimator of probability for all tracks to originate from primary vertex)  will be flexible enough to permit user further tuning of the input variables for the neural net, and of the NN-architecture (number and type of nodes) and training algorithm b c

18. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 17 Towards completion of the Vertex Package b c c (b bkgr) c b Z peak E CM = 500 GeV  test of full chain of C++ ZVTOP with FORTRAN flavour tag and vertex charge imminent  pure FORTRAN results (from SGV) show below:  C++ code for calculation of inputs for flavour tag being written  Vertex charge reconstruction for c-jets under development

19. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 18 Working classes for the LCFI Vertex Package Aim A set of coherent, easy to use classes that contain all the functionality needed for the vertex package. Main task – calculate flavour and charge tag variables, but make flexible enough for future changes and extensions. Current output variables:

20. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 19 Suggestion for a new Vertex class in LCIO +~Vertex() +getMomentum() : const float* +getMass() : float +getCharge() : float +getPosition() : const FloatVec& +getCovMatrix() : const FloatVec& +getChi2() : float +getProbability() : float +getDistanceToPreviousVertex() : float +getErrorDistanceToPreviousVertex() : float +getParameters() : const LCParameters& +getTracks() : const TrackVec& +addTrack() : void +getPreviousVertex() : Vertex&  proposed dedicated Vertex class to be included in LCIO (see left)  negotiations with LCIO developers group are ongoing: may not be implemented in this form, but methods specific to Vertex class will be made available

21. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 20 from: Steve Magill, Digitization simulation using DigiSim and Marlin, talk at Cambridge ILC workshop, April 2006

22. LCFI Oversight Committee Meeting, 12 th July 2006Sonja Hillert (Oxford)p. 21 Vertex charge study for c-jets Victoria Martin  vertex charge (ZVTOP & L/D) and #(c decay tracks) for various decay channels (E CM = 500 GeV)  first results look very promising; next look at corresponding leakage rates and optimise L/D