DØ Hard Diffraction in Run I and Prospects for Run II Andrew Brandt DØ / University of Texas, Arlington Intro and Run I Hard Diffraction Results Forward Proton Detector Low-x Physics 2001 June 28, 2001 Krakow, Poland E  

p p  p p p p  p (p) + X p p  p (p) + j j p p  p p + j j Event Topologies

Event Characteristics

Hard Color-Singlet Exchange Count tracks and EM Calorimeter Towers in |  | < 1.0 jet    (E T > 30 GeV,  s = 1800 GeV) 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 Measure fraction of events due to color-singlet exchange Phys. Lett. B (1998)

1800 and 630 GeV Multiplicities  s = 1800 GeV  s = 630 GeV

SD Event Characteristics

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

hep-ex/

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

Demand gap on one side, measure multiplicity on opposite side Gap Region 2.5<|  |<5.2 Double Gaps at 1800 GeV |Jet  | 15 GeV DØ Preliminary

Demand gap on one side, measure multiplicity on opposite side Gap Region 2.5<|  |<5.2 Double Gaps at 630 GeV |Jet  | 12 GeV DØ Preliminary

n cal Peak at (0,0) indicates diffractive W with a signal on the 1% level   e Measure Mult. Here Measure Mult. Here Diffractive W  s =1800 GeV n cal n L0

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

A Few New Interesting Things Gap fractions at 630 are higher than 1800 for Central Gaps and Hard SD, but comparable for Double Gaps Double gap events with 15 GeV jets are about as rare as top events Diffractive W’s and Z’s have similar gap fractions

Series of 18 Roman Pots forms 9 independent momentum spectrometers allowing measurement of proton momentum and angle. 1 Dipole Spectrometer ( p )  min 8 Quadrupole Spectrometers (p or p, up or down, left or right) t > t min Q4 D S Q3S A1A2 P 1 UP p p Z(m) D1 Detector Bellows Roman Pot FPD Layout p Beam pFpF P P 2 OUT Q2 P 1 DN P 2 IN D2 Q4Q3Q2

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

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 , |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

Run II Event Displays Hard Diffractive Candidate Hard Double Pomeron Candidate

Diffractive Variables p Beam pFpF P For TeV Pomeron Exchange Non-diffractive For ( Note : ) GeV

Acceptance Quadrupole ( p or ) Dipole ( only) Dipole acceptance better at low |t|, large  Cross section dominated by low |t|  Quadrupole Dipole M X (GeV) GeV M X (GeV)   Geometric  Acceptance

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

FPD Commissioning No, it doesn’t work yet, but it will all be ready March 1 October 1!

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

Roman Pot

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

Being completed at UTA Four fibers are aligned together in the frame to make a channel X frame also includes trigger scintillating rod Bicron optical epoxy is used to secure the fibers into the frame once completely assembled After curing, channels are mapped to appropriate location in cookie, PMT calibration fibers are included, lengths are measured and final gluing with optical epoxy is done Detector Construction

FPD Installation All of the castles installed and tested, maintaining vacuum. All the tunnel electronics installed and cables laid. The PU spectrometer is instrumented with full detectors and phototubes. The other vertical pots and dipole spectrometer are instrumented with pseudodetectors (trigger scintillators only) to study halo. Cameras installed and safety review complete 63 MAPMTs have been ordered from Hamamatsu, expected delivery in late August

Castles Installed

Pot Motion: LVDT vs. Encoder

Hit Reconstruction This event (from Engineering Run data) represents a hit in our detector at the location: x d = 5.6 mm y d = 3.8 mm

Run II HSD Improvements Measure , t over large kinematic range Integrated FPD trigger allows large data samples Higher E T jets allow smaller systematic errors Comparing measurements of HSD with track tag vs. gap tag yields new insight into process Can calibrate calorimeter  measurement without MC

June-August Run Plan Dedicated FPD shifts with pots inserted close to beam Start with stand-alone DAQ then integrate into DØ Full system tests Debugging, data-taking, algorithm development, pot insertion procedure, documentation, etc.

Long Range Plan Install 8 more detectors (total of 10) during September shutdown Begin data taking with full DØ detector and trigger list in October Demonstrate working system, usefulness of horizontal plane, and secure funding for remaining MAPMT in 2002 Early papers: NIM Elastic t-distribution Single diffraction distributions Diffractive jet production Double tagged double pomeron exchange

Conclusion Tremendous progress in installation and commissioning Entering a new phase of FPD: 1) Installation almost complete 2) We have funding! Emphasis shifts to software and operations Trigger hardware and firmware still a big concern Starting to think about physics a little!

Run I Bypass Run II S type spool Extended Bypass Dipole (C48-5) Separator Castle Power Leads P type spool Q1Dipole (C48-5) Low Beta Tevatron Reconfiguration (Same for D11 side) BEFORE: AFTER: DØ Separator girder Modified girder Castle Girder modified Bypass construction completed Valves and other vacuum equipment purchased

(Arbitrary Scale) Dipole Region Quadrupole Region FPD Measurements (1 fb -1 )

E t > 15 GeV 10,000 events Soft (1-x) 5 Hard x(1-x)  E t > 15 GeV 0<|t|<3 GeV 2 Hard gg Hard qq FPD Measurements (1 fb -1 )