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Azimuthal distribution of diffractive pions in DIS. Richard Polifka, Charles University, Prague 8. - 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 )
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Azimuthal distribution of diffractive pions in DIS Richard Polifka, Charles University, Prague 8. - 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 Pi+ Picture 2. Schematic diagram of 2 gluon exchange Pi- Pion plane Picture 1. Definition of pion and lepton plane
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 => Pomeron uds
basic cuts • Q2 = < 3.5,100> GeV2 • Run Quality < 3 • Ybjörken=< 0.05 , 0.7 > • | ZVTX | < 35 cm • E-Pz =< 35, 70> GeV • Good 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. Gwilliam • 2 opposite charged tracks in central region coming from primary vertex • Pt > 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 > GeV • No noise in PRT • In 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 happening • weighting 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 events • Not much differencies
E – Pz > 50 GeV Ionisation < 2.3
effects ( from 776 data events) => 626 events left
subtriggers s0 is on in only 24%, s61 in 100% cases 146 from 626 !!
outlook • Too small statistics => 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 => ? • Add data 99 • Put data and mc in better agreement