Leptonic Structure Functions of Photons Klaus Dehmelt Laszlo Baksay Marcus Hohlmann
The Concept of the “Structure of the Photon” 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 SESAPS 2006 K. Dehmelt - November, 11th
Why studying leptonic structure function ? 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 SESAPS 2006 K. Dehmelt - November, 11th
LEP-L3 Experiment at CERN Large Electron Positron Collider LEP SESAPS 2006 K. Dehmelt - November, 11th
L3 – The Detector SESAPS 2006 K. Dehmelt - November, 11th
Two-Photon Interactions with Dimuon 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
Two-Photon Interactions with Dimuon Events (*) (*) Data Sample: Ec.m.s. = 189 … 206 GeV Int. Luminosity = 600 pb-1 SESAPS 2006 K. Dehmelt - November, 11th
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 SESAPS 2006 K. Dehmelt - November, 11th
Two-Photon Interactions with Dimuon Events SESAPS 2006 K. Dehmelt - November, 11th
Dilepton Formalism : density matrix : cross-sections for different helicity states of the photon SESAPS 2006 K. Dehmelt - November, 11th
Dilepton Formalism Extraction of with GALUGA: SESAPS 2006 K. Dehmelt - November, 11th
Dilepton Formalism Extraction of with GALUGA: SESAPS 2006 K. Dehmelt - November, 11th
Cross-Section & Structure-Function VERMASEREN - GALUGA SESAPS 2006 K. Dehmelt - November, 11th
Cross-Section & Structure-Function VERMASEREN - GALUGA Limited x-range due to small Q2 SESAPS 2006 K. Dehmelt - November, 11th
Summary Measurement of differential cross-section and structure-function in the kinematical range Data suggest P2 > 0 SESAPS 2006 K. Dehmelt - November, 11th
Outlook Additional structure functions accessible: FA, FB Interference terms Modulated by and SESAPS 2006 K. Dehmelt - November, 11th
SESAPS 2006 K. Dehmelt - November, 11th
SESAPS 2006 K. Dehmelt - November, 11th