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Interjet Energy Flow

Interjet Energy Flow. Patrick Ryan University of Wisconsin Claire Gwenlan Oxford University April 18, 2005. Monday Meeting http://www-zeus.desy.de/~pryan/rap_gap. Hard Diffractive g p. Use pQCD to study diffraction Hard Diffractive Photoproduction Hard: High E T Jets (E T > 5 GeV)

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Interjet Energy Flow

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  1. Interjet Energy Flow Patrick Ryan University of Wisconsin Claire Gwenlan Oxford University April 18, 2005 Monday Meeting http://www-zeus.desy.de/~pryan/rap_gap

  2. Hard Diffractive gp • Use pQCD to study diffraction • Hard Diffractive Photoproduction • Hard: High ET Jets (ET > 5 GeV) • Diffractive: Gap between jets • Photoproduction: Q2 ~ 0 Standard Diffraction Hard Diffractive gp q Rapidity Gap t

  3. Topology of Rapidity Gaps 2p g Remnant Leading Jet f Leading Trailing Jet Jet Gap g Remnant Trailing 3 Jet 2p 0 h p Remnant f h Distance between jet centers: Dh • ETGap = Total ET between leading and trailing jets • Gap Event: ETGap < ETCut • Gap indicates color singlet exchange -2.4 2.4 0 -3

  4. The Gap Fraction All Dijet Events with large Rapidity separation Dijet Events with large Rapidity separation and ETGap < ETCut • Non-Singlet • f(Dh) decreases exponentially with Dh • Particle production fluctuations  Gap • Non diffractive exchange • Singlet • f(Dh) constant in Dh Expectation for Behavior of Gap Fraction (J.D. Bjorken, V.Del Durca, W.-K. Tung)* fGap fGapn-s fGapSinglet 2 4 3 *Phys. Rev. D47 (1992) 101 Phys Lett. B312 (1993) 225

  5. Simulation of gp EventsZEUS - AMADEUS • PYTHIA 6.1 and HERWIG 6.1 MC • Direct and Resolved MC generated separately • Resolved MC includes Multi Parton Interactions • Dir and Res combined by fitting xg distributions to data (next slide) • PDFs • PDF(p): GRV-LO • PDF(g): WHIT 2 • Color Singlet Exchange MC • PYTHIA: High-t g • Purpose is simply to match the data • Note: Rapidity Gap not due to photon exchange • HERWIG: BFKL • Uses BFKL Pomeron as exchange object in Rapidity Gap events

  6. ZEUS 96-97 Data Luminosity: 38 pb-1 Offline Cleaning Cuts |zvtx| < 40 cm No Sinistra95 e+ with Pe > 0.9, Ee > 5 GeV, ye < 0.85 0.2 < yjb < 0.85 Jet Selection ET1,2 > 5.1, 4.25 GeV (ZUFO) |h1,2| < 2.4 ½|h1 + h2| < 0.75 [(Spx)2 + (Spy)2] / SET < 2 GeV1/2 2.5 < |h1 - h2| < 4.0 4 Gap Samples ETCUT = 0.6, 1.2 1.8, 2.4 GeV (ZUFO) HPP Trigger FLT Slot 42 SLT HiEt I/II/III TLT HPP14 (DST bit 77) ~70,000 Inclusive Events Event Selection and xg FittingZEUS - AMADEUS PYTHIA xgFit to Data Direct + Resolved Direct PYTHIA: 38% Direct + 61% Resolved HERWIG: 54% Direct + 46% Resolved Mixing used in all calculations

  7. Simulation of gp DataZEUS - AMADEUS PYTHIA HERWIG Data well simulated by MC

  8. Simulation of Gap Energy using ZEUS - AMADEUS • HERWIG does not describe Gap Energy • Standard ZEUS HERWIG • Proton PDF: GRV 5 • Photon PDF: WHIT 2 • pTMin = 1.8 GeV • pTMin: Min pT of all scatters in hadronic jet production • Add CS until a reasonable match with data

  9. ET GapAvg Corr. and HZTOOL Tuning Corr. w/ AVG AMADEUS vs. HZTOOL HERWIG Corr. w/ AMADEUS PYT/HER • HZTOOL HERWIG • pTMin = 3.0 GeV • pPDF: CTEQ5L gPDF: SaS 2D

  10. Systematics PYTHIA HERWIG • Order of Variables • +/- 1s: ET1,ET2,h1,h2, ½|h1+h2|,Dh,YJB,pT/ET1/2,ye,Zvtx,ETCut • +/- 3%: ET and YJB (Cal Energy Scale)

  11. Comparisons between Analyses PR: PYTHIA CG: PYTHIA PR: AVERAGE CG: PYTHIA • Agreement between the analyses

  12. Request Preliminary

  13. Summary on gp with Rap Gap • Conclusions • HERWIG + BFKL and PYTHIA + High-t g describe data • Evidence for Color Singlet Exchange • Good Agreement between analyses (P.R & C.G)

  14. Simulation of ETGap PYTHIA HERWIG Data not described by MC

  15. Inclusive and Gap Cross Sections Compare gp Data to HERWIG Inclusive Error bars show stat + sys errors Gap Ratio of above plots Gap Fraction:

  16. Gap Fractions for Different Gap ET • Observed excess of Data over MC without CS exchange • Data has better agreement for MC than without CS • Suggests presence of CS exchange

  17. Previous Preliminary • Preliminary for ICHEP 2002 • Very old • Different binning • Different from CG thesis Preliminary: ● CG ThesisPoints ●

  18. Possible Preliminary

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