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DØ Hard Diffraction in Run I and II

E. f. h. DØ Hard Diffraction in Run I and II. Andrew Brandt (DØ/UTA). DIS2000 April 26, 2000 Liverpool, UK. Learning about the Pomeron. QCD is theory of strong interactions, but 40% of total cross section is attributable to Pomeron

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DØ Hard Diffraction in Run I and II

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  1. E f h DØ Hard Diffraction in Run I and II Andrew Brandt (DØ/UTA) DIS2000 April 26, 2000 Liverpool, UK

  2. Learning about the Pomeron • QCD is theory of strong interactions, but 40% of • total cross section is attributable to Pomeron • exchange -- not calculable and poorly understood • Does it have partonic structure? • Soft? Hard? Super-hard? Quark? Gluon? • Is it universal -- same in ep and ? • Is it the same with and withoutjet production? • Answer questions in HEP tradition -- collide it • with something that you understand to learn • its structure • Note: variables of diffraction aret and x ~ M2 • with FPD measure • without FPD just measure s

  3. EVENT TOPOLOGIES

  4. DØ Calorimeter and Tracking Central Calorimeter End Calorimeter Hadronic Calorimeter Central Drift Chamber (Tracking) ntrk = # charged tracks with |h| < 1.0 EM Calorimeter ncal = # EM towers with ET > 200 MeV and |h| < 1.0 (use E for |h| > 2.0)

  5. h 1 2 4.1 5.2 Gap Definition Detector coverage for gap definition Calorimeter Coverage EM HAD Thresholds: EM: 125 MeV HAD: 500 MeV HAD-END: 50 MeV Level 0 scintillator Gap definitions: 1) Ncal=0 in h (2.0,4.1) 2) Ncal=0 in h (2.0,5.2) 3) Ncal=0 in h (2.5,5.2)

  6. beam . . . . .

  7. Hard Single Diffraction Measure Mult here -4.0 -1.6 h 3.0 5.2 Measure Mult here OR -5.2 -3.0 -1. h 1. 3.0 5.2 Measure Gap Fraction : (diffractive dijet events/all dijet events) @1800 and 630 GeV *Forward Jet Trigger two 12GeV Jets |h|>1.6 * Inclusive Jet Trigger two 15(12)GeV Jets |h|<1.0 Study SD Characteristics: *Single Veto Trigger @1800 and 630 GeV two 15(12)GeV Jets

  8. 1800 and 630 GeV Multiplicities D0 Preliminary s = 1800 GeV s = 630 GeV

  9. 1800 GeV Forward Jet Fit D0 Preliminary Measured gap fraction = 0.65% 0.04% (fit)

  10. Event Characteristics D0 Preliminary

  11. Single Diffractive  Distributions  distribution for forward and central jets using (0,0) bin Dp p = D0 Preliminary central s = 1800 GeV forward central s = 630 GeV forward   0.2 for s = 630 GeV

  12. Single Diffractive Results Measure Multiplicity here or -4.0 -1.6 -1.0 h 1.0 3.0 5.2 Data Sample Measured Gap Fraction (#Diffractive Dijet Events/#All Dijets) 1800 Forward Jets 0.65% + 0.04% - 0.04% 1800 Central Jets 0.22% + 0.05% - 0.04% 630 Forward Jets 1.19% + 0.08% - 0.08% 630 Central Jets 0.90% + 0.06% - 0.06% D0 Preliminary Data Sample Ratio 630/1800 Forward Jets 1.8 + 0.2 - 0.2 630/1800 Central Jets 4.1 + 0.8 - 1.0 1800 Fwd/Cent Jets 3.0 + 0.7 - 0.7 630 Fwd/Cent Jets 1.3 + 0.1 - 0.1 * Forward Jets Gap Fraction > Central Jets Gap Fraction * 630GeV Gap Fraction > 1800GeV Gap Fraction

  13. MC Rate Comparison f visible = gap·f predicted  gap *Add multiplicity to background data distribution *Fit to find percent of signal events extracted  Find predicted rate POMPYT·2 / PYTHIA *Apply same jet  cuts as data, jet ET>12GeV *Full detector simulation D0 Preliminary Evt Sample Hard Gluon Flat Gluon Quark 1800 FWD JET (2.2  0.3)% (2.2  0.3)% (0.8  0.1)% 1800 CEN JET (2.5  0.4)% (3.5  0.5)% (0.5  0.1)% 630 FWD JET (3.9  0.9)% (3.1  0.9)% (2.2  0.5)% 630 CEN JET (5.2  0.7)% (6.3  0.9)% (1.6  0.2)% Evt Sample Soft Gluon DATA 1800 FWD JET (1.4  0.2)% (0.65  0.04)% 1800 CEN JET (0.05  0.01)% (0.22  0.05)% 630 FWD JET (1.9  0.4)% (1.19  0.08)% 630 CEN JET (0.14  0.04)% (0.90  0.06)% * Hard Gluon & Flat Gluon rates higher than observed in data (HG 1800fwd gap~74%±10%, SG 1800fwd gap~22%±3%)

  14. 630 and 1800 GeV Ratios D0 Preliminary Event Sample Hard Glu Flat Glu Quark 630/1800 FWD 1.7  0.4 1.4  0.3 2.7  0.6 630/1800 CEN 2.1  0.4 1.8  0.3 3.2  0.5 1800 FWD/CEN 0.9  0.2 0.6  0.1 1.6  0.3 630 FWD/CEN 0.8  0.2 0.5  0.1 1.4  0.3 Event Sample Soft Glu DATA 630/1800 FWD 1.4  0.3 1.8  0.2 630/1800 CEN 3.1  1.1 4.1  0.9 1800 FWD/CEN 30.  8. 3.0  0.7 630 FWD/CEN 13.  4. 1.3  0.1 * Hard Gluon & Flat Gluon forward jet rate is lower than central jet rate -- and lower than observed in data *Quark rates and ratios are similar to observed *Combination of Soft Gluon and harder gluon structure is also possible for pomeron structure

  15. e Measure Mult. Here Measure Mult. Here  h 1.1 3 5. 2 Diffractive W nL0 s =1800 GeV ncal nL0 ncal Peak at (0,0) indicates diffractive W with a signal on the 1% level

  16. Double Gaps at 630 GeV|Jet h| < 1.0, ET>12 GeV Gap Region 2.5<|h|<5.2 Demand gap on one side, measure multiplicity on opposite side DØ Preliminary

  17. Gap Summary • Pioneered central gaps between jets, 3 papers, 3 Ph. D’s • Observed and measured forward gaps in jet events • at s = 630 and 1800 GeV. Rates much smaller than • expected from naïve Ingelman-Schlein model. • Require a different normalization and significant • soft component to describe data. Large fraction • of proton momentum frequently involved in collision. • Observed jet events with forward/backward gaps • at s = 630 and 1800 GeV • Observed W and Z boson events with gaps • Finalizing papers and attempting to combine results

  18. p pBeam pF P Forward Proton Detector Layout Roman Pot Bellows p Detector A1Q P1Q P1S A1S Q3 Q4 Q4 Q3 Q2 S Q2 S D A2Q AD1 A2S AD2 P2Q P2S 59 57 33 23 0 23 33 Z(m) Series of 18 Roman Pots forms 9 independent momentum spectrometers allowing measurement of proton momentum and angle. 1 Dipole Spectrometer ( p ) x > xmin 8 Quadrupole Spectrometers (p or p, up or down, left or right) t > tmin

  19. Physics Topics with the FPD 1) Diffractive jet production 2) Hard double pomeron exchange 3) Diffractive heavy flavor production 4) Diffractive W/Z boson production 5) New physics 6) Inclusive double pomeron 7) High-|t| elastic scattering 8) Total cross section 9) Inclusive single diffraction FPD allows DØ to maximize Run II physics

  20. Run II Event Displays Hard Diffractive Candidtate Hard Double Pomeron Candidate

  21. Quadrupole Dipole Acceptance x Quadrupole ( p or ) 450 400 350 280 200 MX(GeV) Geometric (f) Acceptance x Dipole ( only) GeV2 450 400 350 280 200 MX(GeV) GeV2 Dipole acceptance better at low |t|, large x Cross section dominated by low |t| x 0 0.02 0.04 1.4 1.4 1.3 2 35 95

  22. Quadrupole + Dipole Spectrometers The combination of quadrupole and dipole spectrometers gives: 1) Detection of protons and anti-protons a) tagged double pomeron events b) elastics for alignment, calibration, luminosity monitoring c) halo rejection from early time hits 2) Acceptance for low and high |t| 3) Over-constrained tracks for understanding detectors and backgrounds

  23. Roman Pot Castle Design Worm gear assembly 50 l/s ion pump Detector Beam Step motor • Constructed from 316L Stainless Steel • Parts are degreased and vacuum degassed • Plan to achieve 10-11 Torr • Will use Fermilab style controls • Bakeout castle, then insert fiber detectors

  24. Roman Pot Arm Assembly Detector is inserted into cylinder until it reaches thin window Threaded Cylinder Motor Bellows Flange connecting to vacuum vessel Thin window and flange assembly

  25. NIKHEF Window • Used finite element analysis to model different window options • Built three types of pots and studied deflection with pressurized helium. • 150 micron foil with elliptical cutout gives excellent results

  26. The Detector Six planes (u,u’,v,v’,x,x’) of 800 m scintillator fibers (’) planes offset by 2/3 fiber 20 channels/plane(U,V)’ 16 channels/plane(X,X’) 112 channels/detector 2016 total channels 80 m theoretical resolution

  27. The Detector 4 Fiber bundle fits well the pixel size of H6568 16 Ch. MAPMT 7 PMT’s/detector (most of the cost) U’ U

  28. Data Taking • No special conditions required • Read out Roman Pot detectors for all events • (can’t miss ) • A few dedicated global triggers for diffractive • jets, double pomeron, and elastic events • Use fiber tracker trigger board -- select • x , |t| ranges at L1, readout DØ standard • Reject fakes from multiple interactions • (Ex. SD + dijet) using L0 timing, silicon • tracker, longitudinal momentum conservation, • and scintillation timing • Obtain large samples (for 1 fb-1): • ~ 1K diffractive W bosons • ~ 3K hard double pomeron • ~500K diffractive dijets with minimal impact on standard DØ physics program

  29. Overall Conclusions DØ has made significant progress in hard diffraction in Run I • • • • A lot more to do in Run II

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