The D0 Forward Proton Detector (FPD) Status

1
The D0 Forward Proton Detector (FPD) Status

• Jorge Barreto
• UFRJ/CBPF - Brazil

pbar
D2 TDC
p
D1 TDC
2
Forward Proton Detector Layout
p
P1U
P2O
Q4
D
Q2
Q3
S
Q2
S
Q4
Q3
A1
A2
D2
D1
P1D
P2I
Veto
59
57
23
33
33
23
0
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 lt t lt 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

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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.
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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
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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 PMTs is attached.
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Segments to Hits

• 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

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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
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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.
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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

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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 PMTs, 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 MAPMTs.
• With this configuration we can read the fiber
  information of only two detectors, although all
  the trigger scintillators are available for
  triggering.

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Quadrupole Elastic Data
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

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

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Elastic Data Distributions
Before 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

After alignment
Gaussian fit
t distribution
DØ Preliminary
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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
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TDC Resolution

• 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
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FPD Trigger and Readout Phase 2
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Standalone Readout vs. AFE Readout

• Standalone 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

y1
x1
D0 Preliminary
x2
y2
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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
X2
Beam
X1
Y1
D0 Preliminary
Y2
X2
?
t (GeV2)
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Dipole Diffraction Results - II
All units in mm

• Shifts ?Y1 ?Y22mm
• Cut the pbar blob (X2 gt -14mm)
• Fair agreement between MC and Data
• More realistic ? and t distributions
• Allow to study ? vs t correlation

D0 Preliminary
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Dipole Diffraction Results - III
Geometrical Acceptance 14s
Data
?
Flat-t distribution
?
0.08
D0 Preliminary
0.06
D0 Preliminary
0.04
0.02
0.
t (GeV2 )
t (GeV2 )
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Run II Diffractive Z ? µµ candidate
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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 gapsjets Double
pomeron with gaps Gap tags vs. proton tags
Topics in RED were studied with gaps only in Run
I
lt100 W boson events in Run I, gt1000 tagged events
expected in Run II
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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