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QCD background for studies with SIMDET

QCD background for studies with SIMDET. A De Roeck CERN A few technical comments. QCD background. The QCD background in a  collider can be large Eg. for L geom ~ 10 35 cm -2 s -1 , 400 nb  cross section  3  events/bunch crossing

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QCD background for studies with SIMDET

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  1. QCD background for studieswith SIMDET A De Roeck CERN A few technical comments QCD background Albert De Roeck (CERN)

  2. QCD background • The QCD background in a  collider can be large Eg. for Lgeom ~ 1035 cm-2 s-1, 400 nb  cross section  3  events/bunch crossing • Many events boosted and/or low mass: no problems • V. Telnov (TESLA TDR appendix): 1.5 central high energy  events for L(z > 0.8zmax) ~ 1.1 .1034 cm-2 s-1 • Should include QCD background for studies and see how relevant variables smear because of this background Can use CLIC tools for TESLA QCD background Albert De Roeck (CERN)

  3. HADES Background files CLIC study: • In e+e- mode  4  events per bunch crossing overlaid on average • Tool developed: HADES (D. Schulte) • Take photon input spectra and generate data base of events of the type   hadrons with PYTHIA Presently PYTHIA 6.136 used (default soft & hard processes) • Now included in SIMDET_V4 (M.Battaglia/HJ. Schreiber) • Steering: via 3 cards BKGR 0 = no background (D) /1 = include background NBKG Average number of background events (REAL/D=0.) # of events is generated according to a Poisson . distribution BKGF UNIT & input file name for the background file QCD background Albert De Roeck (CERN)

  4. HADES Background files for TESLA gamma collider study • Files for TESLA have been prepared e+e- and  files So far catalogued on the CLIC page //clicphysics.web.cern.ch/CLICphysics Only the 200 GeV files done so far  file contains 5000 events • Selection events: W2 > 5 GeV2 , tracks: Pt> 150 MeV,  > 80 mrad (can be changed) photon polarization not taken into account • Note: NOT for background to signal study/only for smearing • A more detailed revisit of QCD ‘tuning’ planned for later this year (R. Godbole visiting CERN) • Further requirements ? QCD background Albert De Roeck (CERN)

  5. Examples: # of particles/event 5000 “events” sampled 63% 95% 36% <#events> = 0.5 <#events> = 1 <#events> = 3 Number of particles in the detector Only events with non-zero activity in the detector QCD background Albert De Roeck (CERN)

  6. Example: Missing ET/event # events # events ET (GeV) ET (GeV) <#events> = 1 <#events> = 3 Et tails to several 10’s of GeV, but on average not much Et QCD background Albert De Roeck (CERN)

  7. Example: transverse and total energy <#events> = 3  > 80 mrad  > 250 mrad Etot (GeV)  > 250 mrad  > 80 mrad Etrans (GeV) QCD background Albert De Roeck (CERN)

  8. Example: transverse and total energy <#events> = 1  > 80 mrad  > 250 mrad Tails! but average values not so bad Etot (GeV)  > 80 mrad  > 250 mrad Etrans (GeV) QCD background Albert De Roeck (CERN)

  9. Example: # of jets <#events> = <#events> = 3  > 80 mrad Jet selection: Cluster algorithm ET(JET) > 5 GeV  > 250 mrad # of jets  > 250 mrad  > 80 mrad About 5-10% of the events with 1 or more jets Etot of each jet (GeV) QCD background Albert De Roeck (CERN)

  10. Example: # of jets <#events> = 1  > 80 mrad  > 250 mrad # of jets QCD background Albert De Roeck (CERN)

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