1. 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

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

3. 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

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

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

6. 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

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

8. 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

9. 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

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

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

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

13. 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

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