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Leptonic Structure Functions of Photons

Leptonic Structure Functions of Photons. Klaus Dehmelt Laszlo Baksay Marcus Hohlmann. Dual nature of photons: uncertainty principle allows photon to fluctuate into various states (leptons, quarks, …) Lifetime of virtual particles: Photon is ideal tool for probing structure of objects.

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Leptonic Structure Functions of Photons

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  1. Leptonic Structure Functions of Photons Klaus Dehmelt Laszlo Baksay Marcus Hohlmann

  2. Dual nature of photons: uncertainty principle allows photon to fluctuate into various states (leptons, quarks, …) • Lifetime of virtual particles: • Photon is ideal tool for probing structure of objects The Concept of the“Structure of the Photon” SESAPS 2006 K. Dehmelt - November, 11th

  3. QED test up to • Measurement of leptonic structure function check for • experimental procedures adopted for QCD • Background to many processes • Calibration process for pp colliders Why studying leptonic structure function ? SESAPS 2006 K. Dehmelt - November, 11th

  4. Large Electron Positron ColliderLEP LEP-L3 Experiment at CERN SESAPS 2006 K. Dehmelt - November, 11th

  5. L3 – The Detector SESAPS 2006 K. Dehmelt - November, 11th

  6. (*) (*) Two-Photon Interactions withDimuon Events Data Sample: Ec.m.s. = 189 … 206 GeV Int. Luminosity = 600 pb-1 • Event Signature: • Single Tagged Electron, High Energy • Deposition in Electromagnetic • Calorimeters • Two tracks, at least one to be identified as a lepton (m) • VERMASEREN Monte Carlo generator SESAPS 2006 K. Dehmelt - November, 11th

  7. (*) (*) Two-Photon Interactions withDimuon Events Data Sample: Ec.m.s. = 189 … 206 GeV Int. Luminosity = 600 pb-1 SESAPS 2006 K. Dehmelt - November, 11th

  8. VSAT: huge background due to proximity to beam pipe L3 Tagging Subdetectors Very Small Angle Tagger – VSAT Luminosity Monitor – LUMI Active Lead Ring – ALR Electromagnetic Calorimeter Endcaps – BGO Endcaps Tagging detectors used to identify scattered electron SESAPS 2006 K. Dehmelt - November, 11th

  9. Two-Photon Interactions withDimuon Events SESAPS 2006 K. Dehmelt - November, 11th

  10. : density matrix : cross-sections for different helicity states of the photon Dilepton Formalism SESAPS 2006 K. Dehmelt - November, 11th

  11. Extraction of with GALUGA: Dilepton Formalism SESAPS 2006 K. Dehmelt - November, 11th

  12. Extraction of with GALUGA: Dilepton Formalism SESAPS 2006 K. Dehmelt - November, 11th

  13. Cross-Section & Structure-Function VERMASEREN - GALUGA SESAPS 2006 K. Dehmelt - November, 11th

  14. Cross-Section & Structure-Function VERMASEREN - GALUGA Limited x-range due to small Q2 SESAPS 2006 K. Dehmelt - November, 11th

  15. Summary • Measurement of • differential cross-section • and structure-function • in the kinematical range • Data suggest P2 > 0 SESAPS 2006 K. Dehmelt - November, 11th

  16. Additional structure functions accessible: FA, FB • Interference terms • Modulated by and Outlook SESAPS 2006 K. Dehmelt - November, 11th

  17. SESAPS 2006 K. Dehmelt - November, 11th

  18. SESAPS 2006 K. Dehmelt - November, 11th

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