Papers of the Week

1
Papers of the Week

• hep-ex/0104001, Study of the effective transverse
  momentum of partons in the proton using prompt
  photons in photoproduction at HERA, ZEUS
  collaboration photoproduction of prompt photons,
  together with an accompanying jet, has been
  measured by the ZEUS collaboration and an
  effective kT value of 1.69 GeV for partons in a
  proton has been determined, within the framework
  of the PYTHIA Monte Carlo. This value is in
  agreement with the trends observed both at fixed
  target energies and at the Tevatron

2
Papers of the Week

• hep-ph/0104052, Parton Distribution Function
  Uncertainties, W. Giele, S. Keller, D. Kosower
  parton distribution functions are presented which
  allow for a quantitative estimate of the relevant
  uncertainties
• hep-ph/0104053, Hard ScatteringBased Luminosity
  Measurement at Hadron Colliders, W. Giele, S.
  Keller a strategy to determine the luminosity at
  hadron colliders using the simultaneous W and Z
  boson counts

3
Reminders of the Week

• Register for the Run 2 MC workshop
  (www-fnal.gov/runiimc)
• Go see Wu Kis WC talk at 4 PM

4
kT in L3(study by Matthis)

• Generate 15000 dijet events with a pT cut of 100
  GeV (left plots) and 10000 dijet events with a pT
  cut of 80 GeV (right plots)
• Upper plots
• ET of leading JetClu(red) and Ktclus(green)
• 2nd row
• ET of Ktclus vs ET of JetClu leading jet
• 3rd row
• Leading Ktclus jet ET in events which would not
  pass JetClu JET100 trigger but would pass Ktclus
  JET100 trigger
• 4th row
• ET of leading JetClu jet for events with leading
  Ktclus jet gt 130 GeV
• All events in distribution would pass a
  JetClu-based Jet100 trigger
• lowest ET is 120 GeV

5
Becoming unratcheted...

• Matthias also conducted a study of a possible fix
  for the ratcheting problem in jet reconstruction
• In the iteration process, he sets the cone radius
  to cone radius/sqrt(2), which reduces the area
  covered by the cone by 50
• reduces influence of energy at the periphery
• He ran the so-modified midpoint algorithm on the
  17 MDC-2 ttbar events, in which the total energy
  contained in JetClu jets was larger by at least
  40 GeV than the total contained in midpoint jets
• Delta sum ET of these events was reduced from gt40
  GeV to between -8 and 3 GeV
• Still need to think about theoretical
  implications

Sum ET difference for 100,000 ttbar
events (midpoint with fix and JetClu)