The D0 Forward Proton Detector (FPD) Status Jorge Barreto UFRJ/CBPF - Brazil pbar D2 TDC p D1 TDC

Forward Proton Detector Layout P1U P2O D S A1 Q2 Q4 Q3 Q2 D2 D1 A2 Q3 Q4 S P1D P2I Veto 59 57 33 23 23 33 Z(m) 9 momentum spectrometers comprised of 18 Roman Pots Scintillating fiber detectors can be brought close (~10 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 GeV2) where the high t range was never before explored at Tevatron energies Allows combination of tracks with high-pT scattering in the central detector

installed in the beam line. 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. A1 Quadrupole castle installed in the beam line.

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 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

Detector Construction At the University of Texas, Arlington (UTA), scintillating and optical fibers were spliced and inserted into the detector frames. The cartridge bottom containing the detector is installed in the Roman pot and then the cartridge top with PMT’s is attached.

Segments to Hits 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 y x 10 u v

Detector Status 10 of the 18 Roman pots have been fully instrumented with detectors Funds to add detectors to the remainder of the pots have recently been obtained from NSF. During the shutdown (Sep-Nov. 2003), the final eight detectors and associated readout electronics are being installed. P2 Quadrupole castle with up and down detectors installed

Pot Motion Software Pot motion is controlled 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.

Operations Currently FPD pots are inserted in every store Commissioning integrated FPD Have some dedicated FPD triggers, more when TM operational Working towards automated pot insertion

Stand-alone DAQ – Phase 1 In phase I we used a stand-alone DAQ (2000 engineering run). We build the trigger with NIM logic using signals given by our trigger PMT’s, veto counters, DØ clock, and the luminosity monitor. If the event satisfies the trigger requirements, the CAMAC module will process the signal given by the MAPMT’s. With this configuration we can read the fiber information of only two detectors, although all the trigger scintillators are available for triggering.

Quadrupole Elastic Data A1U A2U P2D P1D P Pbar Halo Early Hits LM VC In-time hits in AU-PD detectors, no early time hits, or LM or veto counter hits Over 1 million elastic trigger events taken with stand-alone DAQ About 1% pass multiplicity cuts Multiplicity cuts used for ease of reconstruction and to remove halo spray background

Initial Reconstruction Reconstructed  Y (mm) beam P1D X (mm) DØ Preliminary Y (mm) P2D beam =p/p should peak at 0 for elastic events!! Dead Fibers due to cables that have since been fixed X (mm)

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

Elastic Data Distributions Before alignment After alignment After alignment correction, x peaks at 0 (as expected for elastics) The t distribution has a minimum of 0.8 GeV2; tmin is determined by how close the pots are from the beam, shape is in rough agreement with expected angular acceptance from MC. FPD is also a tool helping BD Gaussian fit t distribution DØ Preliminary

TDC Timing from Trigger PMTs tp – tp = 18ns TOF: 197ns 190ns From TDCs : 18ns = (396ns – L1/c) – L1/c 4ns = (396ns – L2/c) – L2/c  L1 = 56.7 m; L2 = 58.8 m DØ Preliminary tp – tp = 4ns Tevatron Lattice: L1 = 56.5m; L2 = 58.7m

TDC Resolution DØ Preliminary Can reject proton halo at dipoles using TDC timing Can see bunch structure of both proton and antiproton beam 1ns ~ 4 TDC channels pbar D2 TDC p DØ Preliminary D1 TDC

FPD Trigger and Readout – Phase 2

Standalone Readout vs. AFE Readout No TDC cut such cut removes lower correlation in y plot Diffracted pbars fall in upper correlation of y plot Uses a trigger based on particles passing through trigger scintillators at detector locations x1 y1 D0 Preliminary x2 y2 AFE readout Uses trigger: one jet with 25GeV and North luminosity counters not firing This trigger suppresses the halo band Similar correlations x1 y1 D0 Preliminary x2 y2

Dipole Diffraction Results - Alignment All units in mm Y1 Y2 Raw data sample has 4640 events Reconstruction of ~50% of events Hit patterns: Misalignment? Hit correlations: pbar halo? Poor  and t distributions X1 Beam X2 X1 Y1 D0 Preliminary Y2 X2  t (GeV2)

Dipole Diffraction Results - II All units in mm Shifts ΔY1= ΔY2=+2mm Cut the pbar blob (X2 > -14mm) Fair agreement between MC and Data More realistic  and t distributions Allow to study  vs t correlation MC Data X1 X2 Y1 Y2  t (GeV2) D0 Preliminary

Dipole Diffraction Results - III Geometrical Acceptance 14σ Data  Flat-t distribution  0.08 D0 Preliminary 0.06 D0 Preliminary 0.04 0.02 0. |t| (GeV2 ) |t| (GeV2 )

Run II Diffractive Z → µµ candidate

DØ Run II Diffractive Topics 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   E <100 W boson events in Run I, >1000 tagged events expected in Run II

Summary and Future Plans Run II analysis still in early stages Early FPD stand-alone analysis shows that detectors work FPD now integrated into DØ readout Commissioning of FPD and trigger in progress Gap results in Run II not yet approved Full 18 pot FPD will start taking data after shutdown (12/03) Tune in next year for first FPD physics results Elastic cross section is used in measurement of luminosity (discrepancy between D0 and CDF)