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Interjet Energy Flow in PHP

Interjet Energy Flow in PHP. Patrick Ryan University of Wisconsin Claire Gwenlan Oxford University June 27, 2005. Monday Meeting http://www-zeus.desy.de/~pryan/rap_gap. Use pQCD to study diffraction Hard Diffractive PHP Hard: High E T Jets (E T > 5 GeV)

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Interjet Energy Flow in PHP

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  1. Interjet Energy Flow in PHP Patrick Ryan University of Wisconsin Claire Gwenlan Oxford University June 27, 2005 Monday Meeting http://www-zeus.desy.de/~pryan/rap_gap

  2. Use pQCD to study diffraction Hard Diffractive PHP Hard: High ET Jets (ET > 5 GeV) Diffractive: Gap between jets Photoproduction: Q2 ~ 0 Rapidity Gap Topology Distance between jet centers: Dh ETGap = Total ET between leading and trailing jets Gap Event: ETGap < ETCut Gap indicates color singlet exchange Rapidity Gap Events q t 2p g Remnant f Leading Jet Dijet Events with large Rapidity separation and ETGap < ETCut Gap ET Trailing Jet p Remnant 0 -2.4 h 2.4 All Dijet Events with large Rapidity separation

  3. 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 • Color Singlet Exchange MC • HERWIG: BFKL • Uses BFKL Pomeron as exchange object in Rapidity Gap events • PYTHIA: High-t g • Purpose is simply to match the data • Note: Rapidity Gap not due to photon exchange

  4. 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 Dijet Selection ET1,2 > 5.1, 4.25 GeV |h1,2| < 2.4 ½|h1 + h2| < 0.75 [(Spx)2 + (Spy)2] / SET < 2 GeV1/2 2.5 < |h1 - h2| < 4.0  Gap Definition 4 Gap Samples ETCUT = 0.5, 1.0 1.5, 2.0 GeV (Hadron) ETCUT = 0.6, 1.2 1.8, 2.4 GeV (Detector) Different Gap ET HPP Trigger FLT Slot 42 SLT HiEt I/II/III TLT HPP14 (DST bit 77) ~70,000 Inclusive Events Event Selection and xgOBS Fitting HERWIG xgOBSFit to Data Direct + Resolved Direct PYTHIA: 30% Direct + 70% Resolved HERWIG: 44% Direct + 56% Resolved (Using Tuned HERWIG/PYTHIA - see later slides) Mixing used to correct data to had level

  5. Gap ET Cross Section Default ZEUS PYTHIA & HERWIG HERWIG PYTHIA • Default MC • Used to unfold data • Plotted vs. Data • MC does not describe data at large Gap ET (region with no CS) • Need good agreement at High Gap ET to establish depletion at Low Gap ET

  6. Large Systematic Differences Default PYTHIA & HERWIG Data Corrected with PYTHIA & HERWIG • Large Sys Differences • Large Systematic Errors • Tuning Procedure • Match unfolded data and HZTOOL prediction in Highest 3 Gap ET bins • Region without CS contribution • Generate AMADEUS using tuned parameters

  7. PYTHIA Tuning • Default ZEUS PYTHIA 6.1 • Proton PDF: GRV94, LO (Set 5) • Photon PDF: SaS2D (Set 3 of SaSph) • pTMin 1= 2.0 • pTMin 2= 1.5 • Modified (Tuned) PYTHIA 6.1 • Based on JetWeb parameters • Proton PDF: CTEQ 5L (Set 46) • Photon PDF: SaS2D (Set 3 of SaSph) • pTMin 1= 1.9 • pTMin 2= 1.7 pTMin 1: pT of Hardest interaction pTMin2: pT of all secondary interactions

  8. HERWIG Tuning • Default ZEUS HERWIG 6.1 • Proton PDF: GRV94 LO (Set 5) • Photon PDF: WHIT-G 2 • Factor to reduce proton radius: 1.0 • Probability of Soft Underlying Event: 1.0 • PTMIN1 = 1.8 GeV • Modified (Tuned) HERWIG 6.1 • Based on JetWeb parameters • Proton PDF: CTEQ 5L (Set 46 of CTEQ) • Photon PDF SaS2D (Set 3 of SaSph) • Factor to reduce proton radius: 3.0 • Probability of Soft Underlying Event: 0.03 • PTMIN1 = 2.7 GeV

  9. Kinematic Variables - HERWIG Default HERWIG Tuned HERWIG • Tuned HERWIG gives better description of Data than default HERWIG

  10. Kinematic Variables – PYTHIA Default PYTHIA Tuned PYTHIA • Tuned PYTHIA gives comparable description of Data • Now have two MCs that describe data well

  11. Gap ET Cross SectionTuned PYTHIA and HERWIG • Reduced systematic difference between HERWIG & PYTHIA • Large Gap ET well described • Unfolding with CS changes cross section in low Gap ET bins ~10% • Color Singlet Contributions • PYTHIA: 3.1% HERWIG 3.8% Unfolded without CS Unfolded with CS

  12. Comparison Between P.R & C.GET Gap PYTHIA Gap ET HERWIG Gap ET Data unfolded with CS Excellent agreement between analyses

  13. Delta Eta Cross Section and Gap Fraction • MC + CS describes data in all regions

  14. Comparison Between P.R & C.GDelta Eta Inclusive Cross Section Delta Eta PYTHIA Delta Eta HERWIG Data unfolded with CS Excellent agreement between analyses

  15. Comparison Between P.R & C.G Delta Eta Gap Cross Section Gap Cross Section HERWIG Gap Cross Section PYTHIA ETCut = 0.5 ETCut = 1.0 ETCut = 1.0 ETCut = 0.5 ETCut = 2.0 ETCut = 1.5 ETCut = 2.0 ETCut = 1.5 Data unfolded with CS Good agreement between analyses (not all MC stats used)

  16. Gap ET Cross Section Unfolded with CS Modified Binning • Original ETGap Binning • Had & Det: 0.5, 1.5, 3.5, 7.0, 12.0 • ETCut in Dh Cross Section • Had: 0.5, 1.0, 1.5, 2.0 • Det: 0.6, 1.2, 1.8, 2.4 • Chosen for max purity & efficiency • Inconsistency between ETGap and Dh cross section plots • Divided Gap ET by 1.2 • Percent CS for modified bins: • PYT: 3.10% HER: 3.38% • Less systematic difference in lower ETGap bins

  17. Comparison Between Bin MethodsET Gap PYTHIA Gap ET HERWIG Gap ET Change ~5% in ETGap cross sections

  18. Comparison Between Bin MethodsGap Cross Sections Gap Cross Section PYTHIA Gap Cross Section HERWIG ETCut = 0.5 ETCut = 0.5 ETCut = 1.0 ETCut = 1.0 ETCut = 1.5 ETCut = 2.0 ETCut = 2.0 ETCut = 1.5 Very small change in Dh Cross Sections

  19. Gap ET Cross Section Request for Preliminary Avg Data Did not renormalize MC Avg Data Refit MC to Avg Data • Average of Data unfolded with PYTHIA and HERWIG • Same data points in both plots, MC curves change

  20. Delta Eta Cross Section Request for Preliminary Avg Data Did not renormalize MC Avg Data Refit MC to Avg Data • Average of Data unfolded with PYTHIA and HERWIG • Same data points in both plots, MC curves change

  21. Gap FractionRequest for Preliminary Avg Data Did not renormalize MC Avg Data Refit MC to Avg Data • Average of Data unfolded with PYTHIA and HERWIG • Same data points in both plots, MC curves change

  22. Interjet Energy Flow Summary • Conclusions • Tuned HERWIG & PYTHIA both describe data well • High Gap ET well described • Reduced systematic difference between data unfolded with HERWIG and PYTHIA • Gap ET & Dh Cross Section well described • Evidence of 3-4%Color Singlet Exchange contribution • Good agreement between P.R. and C.G. analyses • Modification of ETGap bins necessary for consistency • Two methods for displaying MC curves - must choose one • Normalize to Data points unfolded separately with PYT & HER • Normalize to Average of Data unfolded with PYT & HER • Plans • Attempt to make results preliminary for EPS • Write paper

  23. Old vs. New Results Preliminary ICHEP 2002 New Results (P.R. and C.G.) • New Results: Better description of data at large Dh • Improves confidence in CS extraction

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