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LCFI: vertexing and flavour-tagging

Erik Devetak Oxford University. LCFI: vertexing and flavour-tagging. Vertexing Flavour Tagging Charge ID Physics examples Integration into ILD/SiD. CERN-CLIC Meeting 14/05/09. LCFI. 1998-2008 ???. Universities participating (2005-2008):

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LCFI: vertexing and flavour-tagging

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  1. E. Devetak – CERN CLIC Erik Devetak Oxford University LCFI: vertexing and flavour-tagging • Vertexing • Flavour Tagging • Charge ID • Physics examples • Integration into ILD/SiD CERN-CLIC Meeting 14/05/09

  2. E. Devetak – CERN CLIC LCFI 1998-2008 ??? • Universities participating (2005-2008): Bristol, Edinburgh,Glasgow, Liverpool, Nijmegen, Oxford, RAL AIMS • Develop Vertex detector for ILC: point resolution of 3.5 μm • Develop tools that will exploit the vertex detector (vertexing of secondary, tertiary + flavour tagging) • Perform relevant physics analysis

  3. E. Devetak – CERN CLIC The Algorithm • Vertexing of Tracks • Calculation of Discriminating variables • Neural Network using discriminating variables 2 different neural networks with different topologies (built in and FANN) 2 different vertexing algorithms implemented (ZVRES, ZVKIN) 14 discriminatory variables • All Modular • Part of the ILC-Soft Reconstruction Software • Used in both the SiD and ILD detector concepts NIM paper in the process of internal review, package available: http://ilcsoft.desy.de/portal/software_packages/lcfivertex/

  4. E. Devetak – CERN CLIC Vertex Finding D. Jackson, NIM A 388 (1997) 247 Implemented by B. Jeffery and LCFI collaboration • LCFI implemented general ZVRES algorithm: • Represent tracks with Gaussian ´probability tubes´ • Calculate vertex function • Search 3D-space for maxima of this function • Combine close-by vertices - resolve ambiguities Probability Tubes Vertex Function

  5. E. Devetak – CERN CLIC Vertexing - Results • Used sample with CoM = 91.2GeV • Good performance • Also for finding tertiary vertices! • Two Main issues: • One prong Vertices ( one charge track in each vertex!) • Resolving Vertices close to IP

  6. E. Devetak – CERN CLIC Tagging Inputs • Really have three set of inputs: • No secondary vertex found (6 inputs) • At least one secondary vertex found (6 inputs) • Always used Joint Probability (2 Inputs) • Joint Probability = Probability all tracks from primary vertex! • For distribution of tracks from IP, use tracks with negative impact parameters. • Calculate probability track has impact parameter significance larger that what reconstructed • Recombine probabilities of all tracks into single value

  7. E. Devetak – CERN CLIC Tagging Inputs – no sec. vertex • No secondary vertex found → impact parameters significances • Use two tracks with highest significances in z0 and d0! • But also use momentum of these tracks!

  8. E. Devetak – CERN CLIC Tagging Inputs – sec. vertex • Use Vertex information. • Decay length and its significance, momentum of vertex, number of non primary tracks and probability all from same secondary…

  9. E. Devetak – CERN CLIC Pt Corrected Vertex Mass • Most important parameter (particularly for b tagging) • Calculate vertex mass from charged tracks • Use error matrix of vertices to correct for neutrals

  10. E. Devetak – CERN CLIC Combining the Inputs • Data mining problem → many possible techniques • LCFI implemented ad hoc neural network approach. • Trained 9 different networks: • Dependence on number of vertices (1,2,3+) • Definition of signal (b, c, c with b only background) • SiD also tried using FANN package networks • Simpler Method train only 3 networks (b, c, c with b only background) • Always use all Inputs (when available else set to default) • Add 2 Inputs Number of Vertices, Energy of Jet.

  11. E. Devetak – CERN CLIC c (b-bkgr)‏ b c Performance • Performance tested on di-jet events CoM 500 GeV and CoM 91.2GeV • Tested on LDC/ILD and SiD (also with alternative ANN) SiD FANN 500 GeV (SM dijet sample) LDC/ILD 91.2GeV and 500 GeV (SM dijet sample)

  12. E. Devetak – CERN CLIC Performance -2 • Can look at results for each neural network • Test results for different samples c NN output for 1,2,3+ vertex case b tag NN output for 6 jet t-tbar sample

  13. E. Devetak – CERN CLIC Vertex Charge • Package contains also two vertex charge calculation. • Assumption B meson (use all secondary vertices) • Assumption D meson (use only furthest secondary vertex!) • Also tested extension by using more sophisticated reconstructions of many variables; for now • Momentum weighted vertex charge • Momentum weighted jet charge combined in one parameter Combined Charge

  14. E. Devetak – CERN CLIC Physics Example – hadronic ttbar • Often used in the SiD and ILD LOIs • In the Hadronic ttbar example used to: • Reject background • Reduce jet combinatorics • B-bbar quark fb assymetry • But also used in: • H→cc • Additional SiD sbottom analysis • Additional ILD ZHH…

  15. E. Devetak – CERN CLIC Integration in ILD/SiD framework • LCFIVertex has been fully coded in the Marlin ILD/framework. • Makes use of LCIO data structure • Inherits its dependencies. • But works also with SiD: • Detector geometry independent (well almost need fake file to make the framework happy and change one line of code) • Hence can do Sid Reconstruction up to jet finding and then move to LCFI • But you need to install the whole ILD framework! (many dependencies!) • Analysis done in such way are just as valid!

  16. E. Devetak – CERN CLIC Conclusion Ready to be used… should also be easy!NIM paper has been submitted for review. • Presented the LCFI Vertex package. Capabilities: • Vertexing • Flavour Tagging • Charge reconstruction • Showed performance and usage in ILD and SiD Detector! • Flexible and easy to use! • LCIO allows for easy usage of software of both detector concepts! • Gave examples of why it can be a very useful tool! • Physics studies! (very varied)

  17. E. Devetak – CERN CLIC LINKS on How-To presentations: Class Structure -Vertexing http://ilcagenda.linearcollider.org/materialDisplay.py?contribId=53&sessionId=20&materialId=slides&confId=1446 Flavour Tagging Discriminants http://ilcagenda.linearcollider.org/materialDisplay.py?contribId=56&sessionId=20&materialId=slides&confId=1446 Flavour Tagging http://ilcagenda.linearcollider.org/materialDisplay.py?contribId=57&sessionId=20&materialId=slides&confId=1446

  18. E. Devetak – CERN CLIC Other LINKS: Manual (most up to date really) http://ilcsoft.desy.de/portal/e14/e17/e18/infoboxContent324/LCFIVertex-v00-03-refman.pdf Download (here find also information on other ILD packages LCFI Depends on. Note ilcinstall this should install everything for you) http://ilcsoft.desy.de/portal/software_packages/

  19. E. Devetak – CERN CLIC BACKUP

  20. E. Devetak – CERN CLIC

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