Azimuthal distribution of diffractive pions in DIS

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Azimuthal distribution of diffractive pions in DIS

• Richard Polifka, Charles University, Prague
• 8. - 9.12.2005, Antverpen

2
motivation

• Study of diffractive DIS of non resonant di pions
  in invariant mass range 1.1 3 GeV (between ?
  and J/?)
• Looking at angular distribution of pion and
  lepton plane in gamma-p CMS to distinguish
  between 2 gluon exchange model and pomeron
  exchange model

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motivation
Pi
Picture 2. Schematic diagram of 2 gluon exchange
Pi-
Pion plane
Picture 1. Definition of pion and lepton plane
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sources

• DATA 99/00, still using only 00
• MC rapgap inclusive diffraction at medium Q2
  from Tinne Anthonis for 99/00
• Pomeron uds 12 500/1 500 000
• Pomeron c 0/500 000
• Meson 350/3 000 000
• gt Pomeron uds

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basic cuts

• Q2 lt 3.5,100gt GeV2
• Run Quality lt 3
• Ybjörken lt 0.05 , 0.7 gt
• ZVTX lt 35 cm
• E-Pz lt 35, 70gt GeV
• Good electron cuts only 1 electon in elmg
  candidates, E in SpaCal gt 8 GeV, RSpaCal gt 9.1
  cm, excluded some runs because of unfunctional
  clusters

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pion cuts

• Based on Light VM Finder by X. Janssen and
• C. Gwilliam
• 2 opposite charged tracks in central region
  coming from primary vertex
• Pt gt 0.1 GeV
• ? lt 20 , 160 gt
• No neutral particle with E gt 0.4 GeV in Lar or
  SpaCal

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diffractive and noise cuts

• Usually ?MAX lt 3.2, but here not needed
• Xpom lt 0.04
• Invariant Mass lt1.1 , 3 gt GeV
• No noise in PRT
• In first 2 plates of Forward Muon Detector
  allowed some noise

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comparison of data mc

• 12 500 mc x 776 data events gt big error for
  data, my mc more or less describe data gt look
  into mc to see whats happening
• weighting with L4 and L5 weights ( standard HAT
  vars)

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• looking into hadron parton level to see what in
  the event is going on

Good event record
Background event record
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realisation

• Comparing several variables and trying to find
  some, which can on detector level distinguish
  between good and background events
• Not much differencies

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comparison of good and background events
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comparison of good and background events
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E Pz gt 50 GeV
Ionisation lt 2.3
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effects ( from 776 data events)
Variable Cut Effect
E Pz gt 50 GeV 88 cutted
gt 0.7 57 cutted
Ionisation lt 2.3 5 cutted
gt 626 events left
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comparison of data before (old) and after cuts
(new)
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comparison of data and monte carlo
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comparison of data and monte carlo
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subtriggers

• s0 is on in only 24, s61 in 100 cases

146 from 626 !!
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outlook

• Too small statistics gt idea of cone in SpaCal (
  no need to exclude whole SpaCal, many good events
  with radiated gamma)
• Cut on s0 true would brutally decrease
  statistics gt ?
• Add data 99
• Put data and mc in better agreement