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Diffraction at DØ

E. f. h. Diffraction at DØ. Andrew Brandt University of Texas at Arlington. Run I. Run II. Manchesster Workshop December, 2003 Manchester, UK. D Ø Run I Gaps. f. Dh. h. h.

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Diffraction at DØ

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  1. E f h Diffraction at DØ Andrew Brandt University of Texas at Arlington Run I Run II Manchesster Workshop December, 2003 Manchester, UK

  2. DØ Run I Gaps f Dh h h • Pioneered central gaps between jets: Color-Singlet fractions at s = 630 & 1800 GeV; Color-Singlet Dependence on Dh, ET, s (parton-x). PRL 72, 2332(1994); PRL 76, 734 (1996); • PLB 440, 189 (1998) • Observed forward gaps in jet events at s = 630 & 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. • PLB 531, 52 (2002) • Observed W and Z boson events with gaps: measured fractions, properties first observation of diffractive Z. • PLB 574, 169 (2003) • Observed jet events with forward/backward gaps at s = 630 and 1800 GeV

  3. Run II Improvements • Larger luminosity allows search for rare processes • Integrated FPD allows accumulation of large hard • diffractive data samples • Measure , t over large kinematic range • Higher ET jets allow smaller systematic errors • Comparing measurements of HSD with track tag vs. • gap tag yields new insight into process

  4. Run II Rapidity Gap System • Use signals from Luminosity Monitor and Veto Counters (designed at UTA) to trigger on rapidity gaps with calorimeter towers for gap signal • Work in progress (Mike Strang UTA, Tamsin Edwards U. Manchester. Luis Mendoza, Los Andes Columbia) VC: 5.2 < h < 5.9 LM: 2.5 < h < 4.4

  5. Forward Proton Detector p p • 9 momentum spectrometers comprised of 18 Roman Pots • Scintillating fiber detectors can be brought close (~6 mm) to the beam to track scattered protons and anti-protons • Reconstructed track is used to calculate momentum fraction and scattering angle -> Much better resolution than available with gaps alone • Cover a t region (0 < t < 3.0 GeV2) never before explored at Tevatron energies • Allows combination of tracks with high-pT scattering in the central detector P1U P2O Q4 Q3 Q2 Q2 S D Q3 Q4 S A1 D1 A2 D2 P1D P2I Veto 57 59 23 0 33 23 33 Z(m)

  6. DØ Run II Diffractive Topics E   Soft Diffraction and Elastic Scattering: Inclusive Single Diffraction Elastic scattering (t dependence) Total Cross Section Centauro Search Inclusive double pomeron Search for glueballs/exotics Hard Diffraction: Diffractive jet Diffractive b,c ,t , Higgs Diffractive W/Z Diffractive photon Other hard diffractive topics Double Pomeron + jets Other Hard Double Pomeron topics Rapidity Gaps: Central gaps+jets Double pomeron with gaps Gap tags vs. proton tags Topics in RED were studied with gaps only in Run I <100 W boson events in Run I, >1000 tagged events expected in Run II

  7. Tevatron Modifications p AFTER: Bypass Pot Sep Sep Sep Pot Sep Girder Pit Floor Hole in Floor Run II Girder Configuration Bypass BEFORE: Sep Sep Sep p Sep Girder Tunnel Floor Pit Floor Run I Girder Configuration Modifying accelerator takes time and money in this case: 2 years and $300k

  8. Castle Design Worm gear assembly 50 l/s ion pump Thin vaccum window • Constructed from • 316L Stainless Steel • Parts are degreased • and vacuum degassed • Vacuum bettter than • 10-10 Torr • 150 micron vacuum • window • Bakeout castle, THEN • insert fiber detectors Detector Beam Step motor

  9. Castle Status • All 6 castles with 18 Roman pots comprising the FPD were constructed in Brazil, installed in the Tevatron in fall of 2000, and have been functioning as designed. A2 Quadrupole castle installed in the beam line.

  10. Acceptance x Quadrupole ( p or ) 450 400 350 280 200 MX(GeV) Geometric (f) Acceptance x Dipole ( only) GeV2 450 400 350 20 200 MX(GeV) GeV2 Dipole acceptance better at low |t|, large x Cross section dominated by low |t| Combination of Q+D gives double tagged events, elastics, better alignment, complementary acceptance

  11. FPD Detector Design • 6 planes per detector in 3 frames and a trigger scintillator • U and V at 45 degrees to X, 90 degrees to each other • U and V planes have 20 fibers, X planes have 16 fibers • Planes in a frame offset by ~2/3 fiber • Each channel filled with four fibers • 2 detectors in a spectrometer 17.39 mm V’ V Trigger X’ X U’ U 17.39 mm 1 mm 0.8 mm 3.2 mm

  12. Detector Construction At the University of Texas, Arlington (UTA), scintillating and optical fibers were spliced and inserted into the detector frames. DON’T SPLICE The cartridge bottom containing the detector is installed in the Roman pot and then the cartridge top with PMT’s is attached.

  13. Detector Status • 20 detectors built over a 2+ year period at UTA. • In 2001-2002, 10 of the 18 Roman pots were instrumented with detectors. • Funds to add detectors to the remainder of the pots have recently been obtained • from NSF (mostly for MAPMT’s). • During the shutdown • (Sep-Nov. 2003), the final eight • detectors and associated readout • electronics were installed. A2 Quadrupole castle with all four detectors installed

  14. Pot Motion Software Pot motion is controlled by an FPD shifter in the DØ Control Room via a Python program that uses the DØ online system to send commands to the step motors in the tunnel. The software is reliable and has been tested extensively. It has many safeguards to protect against accidental insertion of the pots into the beam. This slide was made before Dec. 4 CDF accident

  15. Operations • Currently FPD expert shifters inserting pots and Captains remove pots and set system to standby • Pots inserted every store • Commissioning integrated FPD • Have some dedicated diffractive triggers, more when Trigger Manager operational • Combine shifts with CFT, since similar readout system • Working towards automated pot insertion (CAP) Commissioning phase long and personnel intensive

  16. Elastic Trigger Halo Early Hits A1U A2U Pbar P P1D P2D LM VC In-time hits in AU-PD detectors, no early time hits, or LM or veto counter hits • Approximately 3 million elastic triggers taken with stand-alone DAQ • About 1% (30,000) pass multiplicity cuts • Multiplicity cuts used for ease of reconstruction and to remove halo spray background

  17. Spectrometer Alignment P1D x vs. P1D x (mm) P1D y vs. P2D y (mm) • Good correlation in hits between detectors of the same spectrometer but shifted from kinematic expectations • 3mm in x and 1 mm in y DØ Preliminary

  18. Elastic Data Distributions After alignment and multiplicity cuts (to remove background from halo spray): =p/p dN/dt Acceptance loss Residual halo contamination  The fit shows the bins that will be considered for corrected dN/dt Events are peaked at zero, as expected, with a resolution of = 0.019

  19. “Final” dN/dt Results After unsmearing and acceptance corrections,the data points were normalized to the points obtained by the E710 experiment The results are in excellentagreementwith the model of M. Bloch showed in the figure Warning: error bars need the contribution of the unsmearing errors  in progress Dr. Jorge Molina, (LAFEX, Brazil) defended his thesis on these results 10/31/03 (first FPD thesis!)

  20. Dipole TDC Resolution • Can see bunch structure of both proton and antiproton beam • Can reject proton halo at dipoles using TDC timing p D2 TDC p halo from previous bunch Timing is important D1 TDC

  21. Fall Shutdown Work Primary Goals:Installation of final 8 detectors and full readout system (new TPP and AFE boards)Tunnel:1) ***Installation and testing of final 8 detectors2) ***Pot motion tests 3) New 12V LVPS installation 4) Amp/shaper tests+repairs for new detectors5) LVDT tests6) Radiaton shielding ; Camera+light work 8) Extension cord work for ORC9) TLDs installedCollision Hall:1) ***Installation and testing of new TPP boards and AFE's2) Cable repairs 3) HV for final detectors4) DFE installationControl Room/Fixed Counting house:1) Automatic pot insertion tests2) Uncabling small control room 3) FPD_LM commissioning in progress4) ACnet+rate watcher mods5) Pots in/out dispaly switch 6) TM commissioning XLab 31) ***Detector assembly Always a lot of work to do in tunnel: access and reliable robust detector, electronics and pot motion system essential

  22. FPD Trigger and Readout

  23. FPD Readout Front View of PW08 (11/10/03)

  24. TPP (Transition Patch Panel) • Interface to connect flat ribbon cables to AFE flex cables. • Decouples tunnel and platform grounds. • Discards extra charge to work within dynamic range of AFE. • Mimics shape of VLPC signals.

  25. Resolution of Noise Problem Old board- 1 cable attached • Large rms pedestsal values with TPP/AFE setup (not seen in test stand) • Traced to a capacitive coupling between grounds • Isolating one of the grounding planes fixes the problem • Required redesign, very tight schedule; new board also has optimized dynamic range S/N=7 10.0 4.0 New board- 1 cable attached

  26. New TPP/AFE Pedestals

  27. Standalone Readout vs. AFE Readout Standalone Readout • Uses a trigger based on particles passing through trigger scintillators at detector locations • No TDC cut • this cut removes lower correlation (halo) in y plot • Diffracted pbars fall in upper correlation of y plot AFE readout • Similar correlations • Uses trigger: • one jet with 25GeV and North luminosity counters not firing • This trigger suppresses the halo band

  28. Dipole Diffraction Results Geometrical Acceptance 14σ (Monte Carlo) Data  Flat-t distribution  0.08 0.06 0.04 0.02 0. |t| (GeV2 ) |t| (GeV2 )

  29. Run II Diffractive Z → µµ Event Display MZ all gap MZ gap muons Tagged Z event in FPD

  30. Summary and Future Plans • Early FPD stand-alone analysis shows that detectors work, will result in elastic dN/dt publication (already 1 Ph.D.) • FPD now integrated into DØ readout (detectors still work) • Commissioning of FPD and trigger in progress • Full 18 pot FPD ready to take data after shutdown (12/03) • Tune in next year for first integrated FPD physics results

  31. Lessons Learned • Bigger project than you (I) might think: more manpower, time, cost, CABLES • Using other people’s electronics is risky • Need a budget and some level of priority (Beyond the Baseline Syndrome) • Early integration is essential • Good contacts in the Accelerator Division are crucial • Halo not well-understood • Grounding issues • Elastics for alignment, redundancy needed • Splicing fibers is painful • Need more access than you might think Not to mention software effort: track reconstruction, Monte Carlo alignment, database, online, etc.

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