1 / 39

ISMD 99 August 11,1999 Brown

Rapidity Gaps at DØ. Jorge Barreto DØ Collaboration / I. Fisica of UFRJ. 1. Introduction 2. Single Diffractive Data @ 1800 & 630 GeV 3. Monte Carlo 4. Hard Double Pomeron Exchange 5. Central Gaps 6. Summary. ISMD 99 August 11,1999 Brown. Diffraction. p p  p p.

shiro
Download Presentation

ISMD 99 August 11,1999 Brown

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Rapidity Gaps at DØ Jorge Barreto DØ Collaboration / I. Fisica of UFRJ 1. Introduction 2. Single Diffractive Data @ 1800 & 630 GeV 3. Monte Carlo 4. Hard Double Pomeron Exchange 5. Central Gaps 6. Summary ISMD 99 August 11,1999 Brown

  2. Diffraction p p  p p p p  p (p) + X p p  p (p) + j j p p  p p + j j

  3. DØ Detector (Forward Gaps) Energy Threshold  coverage EM Calorimeter 150 MeV 2.0<||<4.1 Had Calorimeter 500 MeV 3.2<||<5.2 Central Gaps: EM Calorimeter (200 MeV ET Threshold) Tracking (number of tracks)

  4. L0 Detector beam . . . . .

  5. Event Displays

  6. Hard Single Diffraction Measure Multiplicity here or -4.0 -1.6 -1.0 h 1.0 3.0 5.2 Measure Gap Fraction: *Forward Jet Trigger 2-12GeV Jets |h|>1.6 *46K events @ 1800 *26K events @ 630 * Inclusive Jet Trigger 2-15(12)GeV Jets |h|<1.0 *14K events @ 1800 *27K events @ 630 Study SD Characteristics: *Single Veto Trigger 2-15(12)GeV Jets @ 1800 GeV (22K,38K) @ 630 GeV (1K,24K)

  7. 1800GeV Multiplicities D0 Preliminary NL0 NL0 NCAL NCAL NL0 NL0 NCAL NCAL

  8. 630GeV Multiplicities D0 Preliminary NL0 NL0 NCAL NCAL NL0 NL0 NCAL NCAL

  9. 2D Fitting Signal and Background fit simultaneously Comments: A) Fit background where 2/dof stable. B) If unprobable 2/dof ( >1.0), then to be conservative scale errors by square root. (only needed when large statistics) C) Error statistical and from variation of fit parameters

  10. 1800GeV Forward Jet Fit D0 Preliminary Measured gap fraction = 0.64% 0.05% (fit)

  11. Systematics/cross-checks D0 Preliminary Data Cut 1800 Fwd Jet Fitted Gap Fraction Standard 0.64% + 0.05% - 0.05% Jet Quality Cuts 0.64% + 0.05% - 0.05% Vary Energy Scale +1 0.64% + 0.04% - 0.06% Vary Energy Scale -1 0.62% + 0.04% - 0.05% Luminosity<0.2E30 0.63% + 0.06% - 0.06% Luminosity>0.2E20 0.65% + 0.07% - 0.07% Threshold 1 0.68% + 0.04% - 0.06% (200MeV,600MeV,70MeV) Threshold 2 0.61% + 0.05% - 0.05% (300MeV,700MeV,100MeV) Vary Background fit 0.64% + 0.05% - 0.05% 15GeV Jets 0.62% + 0.05% - 0.04% Measured Fraction is Stable

  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 1800 Forward Jets 0.64% + 0.05% - 0.05% 1800 Central Jets 0.20% + 0.08% - 0.05% 630 Forward Jets 1.23% + 0.10% - 0.09% 630 Central Jets 0.91% + 0.07% - 0.05% D0 Preliminary Data Sample Ratio 630/1800 Forward Jets 1.9 + 0.2 - 0.2 630/1800 Central Jets 4.6 + 1.2 - 1.8 1800 Fwd/Cent Jets 3.2 + 0.8 - 0.5 630 Fwd/Cent Jets 1.4 + 0.1 - 0.1 * Forward Jets Gap Fraction > Central Jets Gap Fraction * 630GeV Gap Fraction > 1800GeV Gap Fraction

  13. 1800GeV Event Characteristics Diffractive Inclusive (solid); Non-Diffractive Inclusive (dashed) D0 Preliminary Diffractive Events Quieter Overall

  14. P p p p  = 1 - xp (momentum loss of proton) P POMPYT Monte Carlo p p  p (or p) + j j * Model pomeron exchange POMPYT26 (Bruni & Ingelman) * based on PYTHIA *define pomeron as beam particle * Structure Functions 1) Hard Gluon xG(x) ~ x(1-x) 2) Flat Gluon (flat in x) 3) Soft Gluon xG(x) ~x (1-x)^5 4) Quark xQ(x) ~ x(1-x) Pomeron Exchanges dominate for  < 0.05

  15. Monte Carlo Multiplicity D0 Preliminary POMPYT NCAL NL0 PYTHIA NCAL NL0

  16. POMPYT Hard Gluon Event Characteristics POMPYT (0,0) inclusive  (solid); PYTHIA (dashed) D0 Preliminary Hard Gluon 1800GeV (0.1) Hard Gluon 630GeV (0.2) POMPYT hard gluon events quieter and jets narrower than PYTHIA events

  17. 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 Quark 1800 FWD JET 2.1%  0.3% 0.9%  0.1% 1800 CEN JET 2.8%  0.5% 0.5%  0.2% 630 FWD JET 4.6%  0.8% 2.2%  0.5% 630 CEN JET 5.1%  0.7%1.4%  0.7% Evt Sample Soft Gluon DATA 1800 FWD JET 1.6%  0.3% 0.64%  0.05% 1800 CEN JET 0.1%  0.1% 0.20%  0.08% 630 FWD JET 0.9%  0.7% 1.23%  0.10% 630 CEN JET 0.1%  0.1% 0.91%  0.07% * Hard Gluon & Flat Gluon rates higher than observed in data *Quark and soft gluon rates are similar to observed (HG 1800fwd gap~74%±11%, SG 1800fwd gap~23%±5%)

  18. CDF Dijet Result 1800 GeV Forward Jets: Calorimeter twr: 2.4<|  |<4.2 BBC: 3.2<|  |<5.9 opposite jets 2 jets ET>20 (1.8<||<3.5) PRL:179 2636 (1997) Rjj = 0.75% ± 0.10% (corrected with Hard Gluon Gap Efficiency) DØ 1800 Forward Gap fraction (w/same correction) = 0.86% ± 0.07%

  19. MC Combined Ratios D0 Preliminary Event Sample Hard Glu Quark DATA 630/1800 FWD 2.2  0.5 2.4  0.61.9 + 0.2 - 0.2 630/1800 CEN 1.8  0.4 2.8  1.4 4.6 + 1.2 - 1.8 1800 FWD/CEN 0.8  0.2 1.8  0.7 3.2 + 0.8 - 0.5 630 FWD/CEN 0.9  0.2 1.6  0.9 1.4 + 0.1 - 0.1 * Hard Gluon & Flat Gluon higher central than forward jet rate --and higher 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

  20.  Calculation Rates, Gap efficiency, Event characteristics all dependent on  probed. *Can use calorimeter only to measure *Weights particles in well-measured region *Can define for all events *Collins (hep-ph/9705393) D0 Preliminary true = calc · 2.2± 0.3 * calculation works well *not dependent on structure function or center-of-mass energy

  21. Single Diffractive  Distribution, 1800GeV * distribution for forward and central jets (0,0)bin: nominal (solid), high (dotted), and low (dashed) D0 Preliminary   0.1 at 1800GeV

  22. Single Diffractive  Distribution, 630GeV * distribution for forward and central jets (0,0)bin: nominal (solid), high (dotted), and low (dashed) D0 Preliminary   0.2 at 630GeV

  23.  Distribution, 1800GeV * distribution for forward and central jets single diffractive (0,0) bin nominal (solid) non-diffractive (calculate to  3.0) (dotted) D0 Preliminary * non-diffractive contribution extends tail *  distribution very different between diffractive and non-diffractive data

  24.  Data/POMPYT * distribution for 1800 GeV jets (0,0) bin nominal Diffractive data (solid); POMPYT Hard Gluon (dashed) D0 Preliminary similar  distributions

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

  26. Double Gaps at 630 GeV Gap Region 2.5<|h|<5.2 DØ Preliminary

  27. Central Gaps Count tracks and EM Calorimeter Towers in ||<1.0 f Dh jet jet (ET > 30 GeV,s = 1800 GeV) h Measure fraction of events due to color-singlet exchange Measured fraction (~1%) rises with initial quark content : Consistent with a soft color rearrangement model preferring initial quark states Inconsistent with two-gluon, photon, or U(1) models Phys. Lett. B 440 189 (1998), hep-ex / 9809016

  28. Fit Results Apply Bayesian fitting method, calculate likelihood relative to “free-factor” model Color factors for free-factor model: Cqq : Cqg : Cgg= 1.0 : 0.04 : 0 (coupling to quarks dominates) Data favor “free-factor” and “soft-color” models “single-gluon” not excluded, but all other models excluded (assuming S not dependent on ET and Dh)

  29. 630 vs 1800 Jet ET > 12 GeV, Jet |h| > 1.9, Dh > 4.0 Opposite-Side Data Same-Side Data 1800 GeV: ncal ntrk ntrk ncal 630 Gev: ncal ncal ntrk ntrk fS 1800(ET =19.2 GeV) = 0.54  0.06stat 0.16sys % fS 630(ET = 16.4 GeV) = 1.85  0.09stat 0.37sys % 630 R1800 = 3.4  1.2

  30. Summary I - SINGLE DIFFRACTIVE DATA: - Measure SD rapidity gap signal at both 1800 GeV and 630 GeV for forward and central jets - Diffractive events quieter and jets thinner than non- diffractive events - Diffractive jet ET distribution matches non-diffractive jet ET -f(forward)>f(central); f(630GeV)>f(1800GeV) 1800 FWD JETS 0.64%  0.05% 1800 CENT JETS0.20%  0.08% 630 FWD JETS 1.23%  0.10% 630 CENT JETS 0.91%  0.07% - Measure SD  distribution (0,0): (higher than expected) -   0.1 @ 1800GeV -   0.2 @ 630GeV POMPYT OBSERVATIONS: - Event Characteristics consistent with harder structures - Rates and ratios prefer quark structure or combination hard/flat gluon with soft gluons II - DOUBLE GAP DATA: - Observe Double Gaps at both 1800 and 630 GeV III - CENTRAL GAPS Phys. Lett. B440 189(1998)

  31. 630GeV Event Characteristics D0 Preliminary

  32. MC Rates D0 Preliminary  Find predicted rate POMPYT·2 / PYTHIA *Apply same jet  cuts as data, jet ET>12GeV *Full detector simulation (error statistical) MC Sample 1800 FWD JET 1800 CENT JET Hard Gluon 2.8%  0.1% 7.1%  0.1% Flat Gluon 3.6%  0.1% 6.2%  0.1% Quark 1.5%  0.1% 2.6%  0.1% Soft Gluon 6.8% 0.1% 1.8%  0.1% MC Sample 630 FWD JET 630 CENT JET Hard Gluon 5.4%  0.1% 10.5%  0.1% Flat Gluon 4.3%  0.1% 10.1%  0.1% Quark 4.2%  0.1% 5.7%  0.1% Soft Gluon 8.6%  0.1% 1.8%  0.1% f visible = f predicted ·gap

  33. POMPYT Hard Gluon Jet ET D0 Preliminary Hard Gluon 630GeV HG 630  0.1 (instead of 0.2) solid line PYTHIA dashed line POMPYT events need  0.1 at 1800GeV and  0.2 at 630GeV to match PYTHIA Jet ET distribution

  34. POMPYT Flat Gluon Event Characteristics D0 Preliminary Flat Gluon 1800GeV (0.1) Flat Gluon 630GeV (0.2) POMPYT Flat Gluon events quieter and jets thinner than PYTHIA events

  35. POMPYT Quark Event Characteristics D0 Preliminary Quark 1800GeV (0.1) Quark 630GeV (0.2) POMPYT quark structrure events quieter and jets thinner than PYTHIA events

  36. POMPYT Soft Gluon Event Characteristics D0 Preliminary Soft Gluon 1800GeV (0.1) Soft Gluon 630GeV (0.2) POMPYT soft gluon jet Et falls faster than PYTHIA

  37. Survival Probability • Assumed to be independent of parton x (ET , Dh) • Originally weak s dependence • Gotsman, Levin, Maor Phys. Lett B 309 (1993) • Recently recalculated • GLM hep-ph/9804404 • Using free-factor and soft-color model • (uncertainty from MC stats and model difference) • with

  38. If color-singlet couples preferentially to quarks or gluons, fraction depends on initial quark/gluon densities (parton x) larger x  more quarks Gluon preference: perturbative two-gluon models have 9/4 color factor for gluons Naive Two-Gluon model (Bj) BFKL model: LLA BFKL dynamics Predictions: fS (ET) falls, fS (Dh) falls/rises Quark preference: Soft Color model: non-perturbative “rearrangement” prefers quark initiated processes (easier to neutralize color) Photon and U(1): couple only to quarks Predictions: fS (ET) & fS (Dh) rise Color-Singlet Models

  39. Use Herwig 5.9 to simulate color-singlet model Includes higher-order effects and DØ detector simulation BFKL two-gluon exchange and t-channel photon exchange processes Divide by QCD prediction to get fS (MC) Construct “coupling factor” models:color-singlet fraction is a function of pdf’s weighted by “coupling factors” fS depends on x (ET,Dh,s) through pdf’s: fS= fnorm{Cqqq1q2 + Cqgq1(2)g2(1) + Cggg1g2} (Cij coupling to initial state ij ) Two-gluon: Cqq=1,Cqg= 9/4,Cgg=(9/4)2 Soft color: Cqq=1/9,Cqg=1/24,Cgg=1/64 Single-gluon: Cqq=Cqg = Cgg= 1 Free-factor: color factors given by fit Monte Carlo Models

More Related