leptonic structure functions of photons
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
73rd Annual Meeting
November 9-11, 2006
Leptonic Structure Functions of Photons
Klaus DehmeltLaszlo Baksay
Marcus Hohlmann
SESAPS 2006K. Dehmelt - November, 11th
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
tE
m pa ir
2
2
SESAPS 2006K. 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
O ( ) 4
SESAPS 2006K. Dehmelt - November, 11th
LEP-L3 Experiment at CERNLarge Electron Positron
Collider LEP
SESAPS 2006K. Dehmelt - November, 11th
L3 – The Detector
SESAPS 2006K. Dehmelt - November, 11th
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 ()• VERMASEREN Monte Carlo generator
SESAPS 2006K. Dehmelt - November, 11th
Two-Photon Interactions withDimuon Events
Data Sample:Ec.m.s. = 189 … 206 GeV
Int. Luminosity = 600 pb-1
(*) (*)
SESAPS 2006K. Dehmelt - November, 11th
L3 Tagging SubdetectorsVery Small Angle Tagger – VSATLuminosity Monitor – LUMIActive Lead Ring – ALRElectromagnetic Calorimeter Endcaps – BGO Endcaps
Tagging detectors used to identify scattered electron
VSAT: huge background due to proximity to beam pipe
SESAPS 2006K. Dehmelt - November, 11th
Two-Photon Interactions withDimuon Events
SESAPS 2006K. Dehmelt - November, 11th
Dilepton Formalism
iM N
PQ PQ,
: density matrix
: cross-sectionsfor different helicitystates of the photon
SESAPS 2006K. Dehmelt - November, 11th
Dilepton Formalism
Extraction of with GALUGA: F QED2 ,
SESAPS 2006K. Dehmelt - November, 11th
Dilepton Formalism
Extraction of with GALUGA: F QED2 ,
SESAPS 2006K. Dehmelt - November, 11th
Cross-Section & Structure-FunctionVERMASEREN - GALUGA
SESAPS 2006K. Dehmelt - November, 11th
Cross-Section & Structure-FunctionVERMASEREN - GALUGA
Limited x-rangedue to small Q2
SESAPS 2006K. Dehmelt - November, 11th
Summary
Measurement ofdifferential cross-sectionand structure-functionin the kinematical range
Data suggest P2 > 0
SESAPS 2006K. Dehmelt - November, 11th
Outlook
• Additional structure functions accessible: FA, FB
Interference terms
• Modulated by and
SESAPS 2006K. Dehmelt - November, 11th
SESAPS 2006K. Dehmelt - November, 11th