Klaus Dehmelt Laszlo Baksay Marcus Hohlmann Investigation of leptonic structure functions with lepton pairs produced in single tagged 2g events. Klaus Dehmelt Laszlo Baksay Marcus Hohlmann

LEP-L3 Experiment at CERN Large Electron Positron Collider LEP FAS 2005 – K. Dehmelt – March, 18th

Why studying leptonic structure function ? QED test up to experimental check for procedures adopted in the study of hadronic structure function Calibration of accelerators with colliding pp beams (LHC) Measurement of transverse and longitudinal leptonic structure functions with two-photon helicity consideration FAS 2005 – K. Dehmelt – March, 18th

FAS 2005 – K. Dehmelt – March, 18th L3 – The Detector FAS 2005 – K. Dehmelt – March, 18th

FAS 2005 – K. Dehmelt – March, 18th Physics at LEP and L3 e+e- - collisions FAS 2005 – K. Dehmelt – March, 18th

Two-Photon Interactions with Dilepton Events Event Signature: Single Tagged Electron, High Energy Deposition in Electromagnetic Calorimeters Two tracks, at least one to be identified as a lepton (m,e) Compare Data to Monte Carlo generated events (DIAG36) FAS 2005 – K. Dehmelt – March, 18th

FAS 2005 – K. Dehmelt – March, 18th Dilepton Kinematics FAS 2005 – K. Dehmelt – March, 18th

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 VSAT: huge background due to proximity to beam pipe FAS 2005 – K. Dehmelt – March, 18th

Study of VSAT VSAT is moved for beam filling  Alignment Studies Huge VSAT background due to scattered beam electrons FAS 2005 – K. Dehmelt – March, 18th

Study of VSAT with mm Cut Acoplanarity of selected two track events FAS 2005 – K. Dehmelt – March, 18th

Study of VSAT with mm Invariant mass distribution of di-lepton events (mm) for 1998-2000, selected with HCAL FAS 2005 – K. Dehmelt – March, 18th

Study of VSAT with mm Invariant mass distribution of di-lepton events (mm) for 1998-2000, selected with MUCH FAS 2005 – K. Dehmelt – March, 18th

FAS 2005 – K. Dehmelt – March, 18th Outlook Determine p contamination Neural Network Method Determine t background Selection of LUMI- , ALR- , and ENDCAP- tagged events Determine Cross-section FAS 2005 – K. Dehmelt – March, 18th

FAS 2005 – K. Dehmelt – March, 18th The Cross-Section FAS 2005 – K. Dehmelt – March, 18th