azimuthal distribution of diffractive pions in dis richard polifka, charles university, prague 8. -...
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Azimuthal distribution of diffractive pions in DIS
Richard Polifka, Charles University, Prague8. - 9.12.2005, Antverpen
motivation
Study of diffractive DIS of non resonant di pions in invariant mass range 1.1 – 3 GeV (between and J/Ψ)
Looking at angular distribution of pion and lepton plane in gamma-p CMS to distinguish between 2 gluon exchange model and pomeron exchange model
motivation
Picture 1. Definition of pion and lepton plane
Picture 2. Schematic diagram of 2 gluon exchange
Pi+
Pi- Pion plane
sources
DATA – 99/00, still using only 00MC – 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=> Pomeron uds
basic cuts
Q2 = < 3.5,100> GeV2
Run Quality < 3Ybjörken = < 0.05 , 0.7 >
| ZVTX | < 35 cmE-Pz = < 35, 70> GeVGood electron cuts: only 1 electon in elmg candidates, E in SpaCal > 8 GeV, RSpaCal > 9.1 cm, excluded some runs because of unfunctional clusters…
pion cuts
Based on Light VM Finder by X. Janssen and C. Gwilliam2 opposite charged tracks in central region coming from primary vertexPt > 0.1 GeV
= < 20° , 160° >No neutral particle with E > 0.4 GeV in Lar or SpaCal
diffractive and noise cuts
Usually MAX < 3.2, but here not needed
Xpom < 0.04
Invariant Mass = <1.1 , 3 > GeVNo noise in PRTIn first 2 plates of Forward Muon Detector allowed some noise
comparison of data & mc
12 500 mc x 776 data events => big error for data, my mc more or less describe data => look into mc to see what’s happeningweighting with L4 and L5 weights ( standard HAT vars)
looking into hadron & parton level to see what in the event is going on
Good event record
Background event record
realisation
Comparing several variables and trying to find some, which can on detector level distinguish between good and background eventsNot much differencies
effects ( from 776 data events)
Variable Cut Effect
E – Pz > 50 GeV 88 cutted
> 0.7 57 cutted
Ionisation < 2.3 5 cutted
)(
)(
ePt
Pt
=> 626 events left