AZIMUTHAL DISTRIBUTIONOF

DIJETSIN

DIFFRACTIVE DIS

David Šálek

December 8, 2005

Diffractive Meeting, Antwerpen

BOSON GLUON FUSION & TWO GLUON EXCHANGE MODEL

AZIMUTHAL ANGLE

definition of the azimuthal angle in gamma-p CMS

CUTS

Kinematical cuts: 8 < Q2 < 100

-35 < zvertex < 35

0.05 < yBjorken < 0.7

35 < E - pz < 70

Scattered electron cuts: Espacal > 8

Rspacal > 9.1

Jet cuts: pT > 3.5

-3 < etagamma-p < 0

Diffractive cuts: etamax < 3.2

PRT 0, 1, 2, 3, 4 < 1

FMD 0+1, 2 < 2

xPomeron < 0.04

DATA

99-00 data

sub-trigger 61

prescale < 15

1223 events

MONTE CARLO

RAPGAP inclusive diffraction for F2D(3) at medium Q2

generator: RAPGAP 2.08/18

files from Tinne Anthonis for 99-00

pomeron uds N = 5000000

L = 205.39 pb-1

pomeron c N = 500000

L = 179.16 pb-1

meson N = 4489194

L = 95.36 pb-1

Boson Gluon Fusion4344 events QCD Compton

MONTE CARLO

QUARK & GENERATED JET CORELATION

LEADING JET

QUARK & GENERATED JET CORELATION

SECOND JET

GENERATED & RECONSTRUCTED JET CORELATION

LEADING JET

GENERATED & RECONSTRUCTED JET CORELATION

SECOND JET

AZIMUTHAL ANGLE

Problemat

generator level:

no W-shape

Problemat

reconstructed level:

Lorentz transformation

PROBLEM AT GENERATOR LEVEL

azimuthal distribution is not smooth

LORENTZ TRANSFORMATION

gamma-p CMS:

4-vector of incoming proton4-vector of exchanged gamma q = k – k’

k’ not correctly reconstructed

it results in deviation of azimuthal distribution at reconstructed level

GENERATED & RECONSTRUCTED ELECTRON

CORELATION BETWEEN GENERATOR & RECONSTRUCTED LEVEL

SCATTERED ELECTRONENERGY

xPomeron & etamax

CORELATION BETWEEN GENERATOR & RECONSTRUCTED LEVEL

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 wherethere is only the scattered electron in spacal

etaLab > -1

zvertex & BASIC KINEMATICAL VARIABLES

SCATTERED ELECTRON

xgamma & E - pz

DIFFRACTIVE VARIABLES

FORWARD MUON DETECTORSPROTON 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

JET CHARACTERISTICS

LEADING JET

SECOND JET

HFS CALIBRATION ???

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