1. AZIMUTHAL DISTRIBUTION OF DIJETS IN DIFFRACTIVE DIS David Šálek December 8, 2005 Diffractive Meeting, Antwerpen

2. BOSON GLUON FUSION & TWO GLUON EXCHANGE MODEL

3. AZIMUTHAL ANGLE definition of the azimuthal angle in gamma-p CMS

4. CUTS Kinematical cuts:8 < Q 2 < 100 -35 < z vertex < 35 0.05 < y Bjorken < 0.7 35 < E - p z < 70 Scattered electron cuts:E spacal > 8 R spacal > 9.1 Jet cuts:p T > 3.5 -3 < eta gamma-p < 0 Diffractive cuts:eta max < 3.2 PRT 0, 1, 2, 3, 4 < 1 FMD 0+1, 2 < 2 x Pomeron < 0.04

5. DATA 99-00 data sub-trigger 61 prescale < 15 1223 events

6. MONTE CARLO RAPGAP inclusive diffraction for F 2 D(3) at medium Q 2 generator: RAPGAP 2.08/18 files from Tinne Anthonis for 99-00 pomeron udsN = 5000000 L = 205.39 pb -1 pomeron cN = 500000 L = 179.16 pb -1 mesonN = 4489194 L = 95.36 pb -1 Boson Gluon Fusion 4344 events QCD Compton

7. MONTE CARLO

8. QUARK & GENERATED JET CORELATION LEADING JET

10. QUARK & GENERATED JET CORELATION SECOND JET

12. GENERATED & RECONSTRUCTED JET CORELATION LEADING JET

14. GENERATED & RECONSTRUCTED JET CORELATION SECOND JET

16. AZIMUTHAL ANGLE Problem at generator level: no W-shape Problem at reconstructed level: Lorentz transformation

17. PROBLEM AT GENERATOR LEVEL azimuthal distribution is not smooth

18. LORENTZ TRANSFORMATION gamma-p CMS: 4-vector of incoming proton 4-vector of exchanged gamma q = k – k’ k’ not correctly reconstructed it results in deviation of azimuthal distribution at reconstructed level

19. GENERATED & RECONSTRUCTED ELECTRON

20. CORELATION BETWEEN GENERATOR & RECONSTRUCTED LEVEL SCATTERED ELECTRON ENERGY

21. x Pomeron & eta max CORELATION BETWEEN GENERATOR & RECONSTRUCTED LEVEL

22. COMPARISON OF DATA & MONTE CARLO dead spacal region problem with final state radiation: electron properties basic kinematic variables Lorentz transformation temporary solution: take only those events where there is only the scattered electron in spacal eta Lab > -1

23. z vertex & BASIC KINEMATICAL VARIABLES

24. SCATTERED ELECTRON

25. x gamma & E - p z

26. DIFFRACTIVE VARIABLES

27. FORWARD MUON DETECTORS PROTON REMNANT TAGGER way to improve agreement between data and MC: FMD noise good agreement needed only to calculate luminosity correctly adding FMD noise decreases MC statistics

28. JET CHARACTERISTICS

29. LEADING JET

30. SECOND JET

31. HFS CALIBRATION ???

32. SUMMARY & OUTLOOK retrieve W-shaped azimuthal distribution for BGF at parton level reconstruct electron properties better in order to reveal generated azimuthal distribution at reconstructed level increase statistics by including events with final state radiation with proper corrections to radiated gammas generate Monte Carlo files with two gluon exchange unfolding