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Diffractive Results from

Diffractive Results from. Brian Cox. Workshop on low x physics, Antwerp 2002. Diffractive W and Z Observation of double diffractive dijets Run 1 highlights Run II Beginnings. E. . . Diffraction in the DØ detector. L0 Detector. n L0 = # hit tiles in L0 detector.

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Diffractive Results from

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  1. Diffractive Results from Brian Cox Workshop on low x physics, Antwerp 2002 • Diffractive W and Z • Observation of double diffractive dijets • Run 1 highlights • Run II Beginnings E  

  2. Diffraction in the DØdetector L0 Detector nL0 = # hit tiles in L0 detector ncal = # cal towers with energy above threshold beam Central Calorimeter End Calorimeter EM Calorimeter Energy Threshold  coverage EM Calorimeter 150 MeV 2.0<||<4.1 Had Calorimeter 500 MeV 3.2<||<5.2 Hadronic Calorimeter

  3. Diffractive W and Z production Central and Forward electron W Event and Z event selections: Start with Run1b W en and Z ee candidate samples DØ Preliminary

  4. Diffractive selection • Measure forward calorimeter tower multiplicities in range3.0<|h|<5.2 • Look at minimum multiplicity side of detector (not necessarily opposite side to electron)

  5. Central W Multiplicity Minimum side   -1.1 0 1.1 3.0 5.2 nL0 L0 ncal ncal Peak at (0,0) is diffractive W-boson Signal: 68 of 8724 events in (0,0) bin DØ Preliminary

  6. Forward W multiplicity Minimum side   -2.5 -1.1 0 1.1 3.0 5.2 nL0 ncal L0 Peak at (0,0) indicates forward diffractive W-boson in forward electron sample: 23 of 3898 events in (0,0) bin DØ Preliminary

  7. Central W event distributions Standard W Events Diffractive W Candidates Electron ET ET=35.16 Neutrino ET ET=36.08 ET=37.12 MT=70.64 Transverse Mass MT=70.71 ET=35.27 DØ Preliminary

  8. Z multiplicity Minimum side   -2.5 -1.1 0 1.1 3.0 5.2 L0 ncal Peak at (0,0) indicates diffractive Z-boson: 9 of 811 events in (0,0) bin DØ Preliminary

  9. Extracting the Signal • 2-D fits of multiplicity plots Fit Data Fit Background Fit Signal

  10. Use high statistics background Solid line: Central W Dashed: Cen+Fwd W ncal Solid line: Central W Dashed: Cen+Fwd W ncal DØ Preliminary Background shapes agree, but fit more reliable with higher stats

  11. Results *Observed clear Diffractive W and Diffractive Z signals *Measured Diffractive W/All W and Diffractive Z/All Z Sample Diffractive Probability Background All Fluctuates to Data Central W (1.08 + 0.21 - 0.19)% 1 x 10-137.7s Forward W (0.64 + 0.19 - 0.16)% 6 x 10-75.3s All W (0.89 + 0.20 – 0.19)% Z (1.44 + 0.62 - 0.54)% 5 x 10-54.4s CDF {PRL 78 2698 (1997)} measured RW = 1.15 ± 0.55% with a significance of 3.8 DØ Preliminary

  12. A challenge to the Monte Carlos: W + jet and forward / central W production rates b(1-b) SampleDataQuark Hard GluonCenW(1.08 + 0.21 - 0.19)%(4.1  0.8)%(0.15  0.02)% ForW(0.64 + 0.19 - 0.16)%(7.2  1.3)% (0.25  0.04)% Z(1.44 + 0.62 - 0.54)%(3.8  0.7)% (0.16  0.02)% W + jet rates : very sensitive to IP structure Jet ETDataQuark Hard Gluon >8GeV(10 ± 3)%14-20% 89 % >15GeV (9 ± 3)%4-9 % 53 % >25GeV (8 ± 3)%1-3 % 25 % DØ Preliminary

  13. Double Diffraction at 1800 GeV |Jet h| < 1.0, ET>15 GeV Gap Region 2.5<|h|<5.2

  14. Double Diffraction at 630 GeV |Jet h| < 1.0, ET>12 GeV Gap Region 2.5<|h|<5.2

  15. Gaps Between Jets f Dh jet jet h Cox, Forshaw & Lonnblad, JHEP10 (1999) 023 Enberg, Ingleman & Motyka Phys. Lett. B524:273-282,2002

  16. Diffractive Dijets at 630 and 1800 GeV Measure Multiplicity here or -4.0 -1.6 -1.0 h 1.0 3.0 5.2 Forward jet trigger ET > 12 GeV Central jet trigger ET > 15 (12) GeV @ 1800 (630) GeV Data Sample Measured Gap Fraction 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% * Forward Jets Gap Fraction > Central Jets Gap Fraction * 630 GeV Gap Fraction > 1800 GeV Gap Fraction • Monte Carlo analysis (hep-ex/9912061) – gluon dominated IP (hard + soft) + reduced flux factor accounts for data

  17. Diffractive Dijets at 630 and 1800 GeV central s = 1800 GeV forward central s = 630 GeV forward

  18. The Run II Pots • 8 detectors fully installed (D1, D2, A1I, A2I, P1U, P1D, P2D) • All will be in place after October shutdown

  19. Acceptance of quadrupole pots

  20. Data distributions Elasticx distribution peaks at 0 DØ not Preliminary at all really

  21. Highlights • Two new Run I analyses due for publication : • Diffractive W (+ jets) and Z • Double Diffractive Dijets • We’re all looking forward to Run II analysis ! • Detectors working fine • First physics in December / January

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