June 2003 M.Mulders - Fermilab 1 Diffractive results from DØ and prospects for Run II Martijn Mulders Fermilab for the DØ collaboration (with special thanks to C. Royon, M. Strang, A. Brandt, J. Womersley and L.Coney for plots and useful discussions) Xth Blois Workshop on Elastic and Diffractive Scattering, Helsinki, June 2003

June 2003 M.Mulders - Fermilab 2 Tevatron at Fermilab p pp Run I ( ) :  s =1.8 TeV Run II ( ? ) :  s =1.96 TeV Batavia, Illinois Main Injector & Recycler Tevatron Booster pp p  p source Chicago CDF DØ

June 2003 M.Mulders - Fermilab 3 Examples of Soft Diffraction Modeled by Regge Theory Non-perturbative QCD No quantum number exchanged –Synonymous with exchange of a Pomeron

June 2003 M.Mulders - Fermilab 4 Examples of Hard Diffraction Described by Different Models –DGLAP based (q/g partonic structure of Pomeron) –BFKL based (gluon ladder structure of Pomeron) –Soft Color Interactions (non-perturbative effects of standard QCD) Diffractively Produced Jets Diffractively Produced W

June 2003 M.Mulders - Fermilab 5 Why study Diffractively Produced W?

June 2003 M.Mulders - Fermilab 6 Particle Kinematics The total center of mass energy is sqrt (s) The standard four-momentum transfer |t| is defined as –|t| = (p f – p i ) 2 –|t| ~    (the scattering angle) The momentum fraction (  ) taken by the Pomeron is defined as –  = 1 – x p = 1 – p f / p i Diffraction dominates for  < 0.05 Maximum diffractive mass (M x ) available is –M x = sqrt (  s) pipi pfpf IP

June 2003 M.Mulders - Fermilab 7 Hard Diffraction W boson has 80 times the mass of the proton !! How can proton stay intact ?? 100 times

June 2003 M.Mulders - Fermilab 8 Experimental Signature:

June 2003 M.Mulders - Fermilab 9 DØ Detector (Run I) EM Calorimeter L0 Detector (n l0 = # tiles in L0 detector with signal 2.3 < |  | < 4.3) End Calorimeter Central Calorimeter (n cal = # cal towers with energy above threshold) Hadronic Calorimeter Forward Gaps EM Calorimeter E > 150 MeV 2.0 < |  | < 4.1 Had. Calorimeter E > 500 MeV 3.2 < |  | < 5.2)

June 2003 M.Mulders - Fermilab 10 Z boson sample: Start with Run1b Z ee candidate sample Central and forward electron W boson sample: Start with Run1b W e candidate sample Data Samples

June 2003 M.Mulders - Fermilab 11 Multiplicity in W Boson Events   Minimum side Peak at (0,0) indicates diffractive W boson signal (91 events) DØ Preliminary Plot multiplicity in 3<|  |<5.2

June 2003 M.Mulders - Fermilab 12 W Boson Event Characteristics M T =70.4 E T =36.9 E T =35.2 Standard W Events Diffractive W Candidates E T =35.1 E T =37.1 M T =72.5 DØ Preliminary

June 2003 M.Mulders - Fermilab 13 Multiplicity in W Boson Events DØ Preliminary diffractive Non-diffractive

June 2003 M.Mulders - Fermilab 14 Observation of Diffractive W/Z Observed clear Diffractively produced W and Z boson signals fraction diffractive significance over Sample over All background Central W( )% 7.7  Forward W( )% 5.3  All W( – 0.17)% 7.5  All Z ( )% 4.4  DØ Preliminary Background from fake W/Z gives negligible change in gap fractions

June 2003 M.Mulders - Fermilab 15 R D =  (W D ) /  ( Z D ) = R*(W D /W)/ (Z D /Z) where W D /W and Z D /Z are the measured gap fractions from this measurement and R=  (W)/  (Z) = ±0.15 (stat) ±0.20 (sys)±0.10 (NLO) B. Abbott et al. (D0 Collaboration), Phys. Rev D 61, (2000). Substituting in these values gives R D = This value of R D is somewhat lower than, but consistent with, the non-diffractive ratio. DØ Preliminary W/Z Cross Section Ratio

June 2003 M.Mulders - Fermilab 16 Calculate  =  p/p for W boson events using calorimeter : Diffractive W Boson   data  E t i e y i /2E Sum over all particles in event: those with largest E T and closest to gap given highest weight in sum (particles lost down beam pipe at –  do not contribute Use only events with rapidity gap {(0,0) bin} to minimize non-diffractive background Correction factor derived from MC used to calculated data  DØ Preliminary

June 2003 M.Mulders - Fermilab 17 CDF {PRL (1997)} measured R W = (1.15 ± 0.55)% for |  |<1.1 where R W = Ratio of diffractive/non-diffractive W (a significance of 3.8  ) This number is corrected for gap acceptance using MC giving 0.81 correction, so uncorrected value is (0.93 ± 0.44)%, consistent with our uncorrected data value: We measured ( –0.17)% for |  |<1.1 Uncorrected measurements agree, but corrections derived from MC do not… Our measured(*) gap acceptance is (21 ± 4)%, so our corrected value is 5.1% ! (*) : derived from POMPYT Monte Carlo Comparison of other gap acceptances for central objects from CDF and DØ using 2-D method: DØ central jets 18% (q) 40%(g) CDF central B 22%(q) 37% overall CDF J/  29% It will be interesting to see Run II diffractive W boson results! DØ / CDF comparison

June 2003 M.Mulders - Fermilab 18   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 1000 tagged events expected in Run II DØ Run II Diffractive Topics

June 2003 M.Mulders - Fermilab 19 D0 Run II integrated luminosity

June 2003 M.Mulders - Fermilab 20 D0 Run II data taking efficiency

June 2003 M.Mulders - Fermilab 21 Run I  Run II: DØ Upgrade All New Inner Tracker New Muon Detectors & Shielding Faster readout electronics New Trigger, DAQ, and offline software 2 Tesla Solenoid Magnet Silicon Vertex Detectors Preshower Detectors Scint. Fiber Tracker

June 2003 M.Mulders - Fermilab 22 Rapidity Gap System Run II Use signals from Luminosity Monitor (and later Veto Counters) to trigger on rapidity gaps with calorimeter towers for gap signal Use calorimeter at Level 2 to further refine rapidity gaps VC: 5.2 <  < 5.9 LM: 2.7 <  < 4.4

June 2003 M.Mulders - Fermilab 23 Calorimeter Energy for Gap Triggers DØ Preliminary Gap+ Jet Trigger North Gap + Jet Trigger South EM energy North EM energy South

June 2003 M.Mulders - Fermilab 24 Leading Jet E T Inclusive Jets North Gap Jets South Gap JetsDouble Gap Jets E T (GeV) DØ Preliminary

June 2003 M.Mulders - Fermilab 25 Forward Proton Detector Layout 9 momentum spectrometers composed 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 < 4.5 GeV 2 ) never before explored at Tevatron energies Allows combination of tracks with high-p T scattering in the central detector D S Q2Q2 Q3Q3 Q4Q4 S A1A1 A2A2 P 1U P 2I P 2O P 1D p p Z(m) D2 D Veto Q4Q4 Q3Q3 Q2Q2

June 2003 M.Mulders - Fermilab 26 Quadrupole and Dipole acceptance Quadrupole ( p or p ) : Dipole ( p only) : _ _  

June 2003 M.Mulders - Fermilab 27 FPD Detector Setup 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 channels, X planes have 16 channels Planes in a frame offset by ~2/3 fiber Each channel filled with four fibers 2 detectors in a spectrometer 0.8 mm 3.2 mm 1 mm mm U U’ X X’ V V’ Trigger

June 2003 M.Mulders - Fermilab 28 Segments to Hits y x 10  y u x v Segments (270  m) Combination of fibers in a frame determine a segment Need two out of three possible segments to get a hit –U/V, U/X, V/X Can reconstruct an x and y Can also get an x directly from the x segment Require a hit in both detectors of spectrometer

June 2003 M.Mulders - Fermilab 29 Tagged Elastic Trigger NO HITS IN LMN OR LMS OR VCN OR VCS NO EARLY HALO HITS IN A1U-A2U, P1D-P2D IN TIME HITS IN A1U-A2U, P1D-P2D A1UA2U P2DP1D P Pbar Halo Early Hits Approximately 3 million raw elastic events About 1% (30 thousand) pass multiplicity cuts (used for ease of reconstruction and to try to handle high halo background from Tevatron) 1 or 0 hits in each of 12 planes of the PD spectrometer Each frame of both PD detectors needs a valid segment (i.e. 6 segments total) Segments turned into hits and then reconstructed into tracks

June 2003 M.Mulders - Fermilab 30  =  p/p should peak at 0 for elastic events!! Dead Fibers due to cables that have since been fixed P1D P2D beam Y X Y Reconstructed  beam DØ Preliminary Initial Reconstruction

June 2003 M.Mulders - Fermilab 31 Spectrometer Alignment Good correlation in hits between detectors of the same spectrometer but shifted from kinematic expectations –3mm in x and 1 mm in y P1D x vs. P2D x (mm) P1D y vs. P2D y (mm) DØ Preliminary

June 2003 M.Mulders - Fermilab 32 Distributions after Alignment Correction After correction,  now peaks at 0 –MC  resolution is (including z smearing and dead channels), data is 0.015, 1.15 times larger The t distribution has a minimum of 0.8 GeV 2. t min is determined by how close the pots are from the beam (would expect 0.6 GeV 2 with clean beam). Shape is in agreement with expected angular acceptance from MC. |t| (GeV 2 )  -reco DØ Preliminary

June 2003 M.Mulders - Fermilab 33 TDC Timing from Trigger Tubes From TDCs : 18ns = (396ns – L1/c) – L1/c 4ns = (396ns – L2/c) – L2/c  L1 = 56.7 m; L2 = 58.8 m Tevatron Lattice: L1 = 56.5m; L2 = 58.7m TOF: 197ns 190ns t p – t p = 18ns t p – t p = 4ns DØ Preliminary

June 2003 M.Mulders - Fermilab 34 TDC Resolution Can see bunch structure of both proton and antiproton beam Can reject proton halo at dipoles using TDC timing D1 TDC D2 TDC pbar p

June 2003 M.Mulders - Fermilab 35 Conclusions First observation of diffractively produced Z bosons. Measurement of W D /W, Z D /Z and W D /Z D Early stand-alone analysis FPD (with 10 out of 18 Roman Pots) shows that detectors work FPD is now fully integrated in D0 readout Installation remaining pots later this year, and further commissioning FPD and trigger in progress Definition of rapidity gaps in Run II detector underway. Inclusion of FPD (anti-)proton tags expected soon Expect rich D0 diffractive physics program in Run II !!