D DiffractionForward Proton Detector Update

1
DØ Diffraction/Forward Proton Detector Update

• Andrew Brandt
• University of Texas at Arlington

Run I
Goals of talk Present FPD status Reality check
for 420m project Results relevant for 420m project
Run II
Manchester Workshop December 14, 2004
Manchester, UK
2
DØ Run I Gaps

• 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 Forward Proton Detector (FPD) allows
  accumulation of large hard diffractive data
  samples
• Measure ?, t over large kinematic range
• Higher ET jets allow smaller systematic errors
• Comparing measurements with track tag vs.
• gap tag yields new insight into processes

4
Diffractive Topics and Students!
5
Forward Proton Detector (FPD)
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 (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 lt t lt 3.0 GeV2) never before
  explored at Tevatron energies
• Allows combination of tracks with high-pT
  scattering in the central detector

6
Tevatron Modifications
Bypass
BEFORE
Sep
Sep
Sep
Modify low beta quad girders, make new extended
bypasses (21 spare)
p
Sep Girder
Tunnel Floor
Pit Floor
Run I Girder Configuration
Modifying accelerator takes time and money in
this case 2 years and 300k (cryo engineering
not included)
7
Detector/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.
• 20 detectors built over a 2 year period at UTA
• In 2001-2002, 10 of the 18 Roman pots were
  instrumented with detectors.
• During the fall 2003 shutdown the final eight
  detectors and associated readout
• electronics were installed.

A2 Quadrupole castle with all four detectors
installed
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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. CDF pots (controlled by Beams Div.)
accident in 12/03 grounded TeV for 2 weeks, DØ
pots for 1 month, CDF pots for seveeral months
(who moves pots and how are key issues)
9
Operations

• Operations in 2004 have been routine, only
  occasional minor problems, much less than average
  sub-detector
• Currently FPD expert shifters inserts pots and
  Captains remove pots and set system to standby
• 18 pots inserted every store when lumlt45E30, read
  out for
• all events
• Combine shifts with CFT, since similar readout
  system,
• standard FPD fiber plots incorporated into
  CFT online
• examine program
• Working towards automated pot insertion by shift
  captain

10
Detector Hit Resolutions

• Starting in January 2004, all 18 detectors
  regularly inserted (dipoles since February 2003)
• Resolutions calculated by the difference of the x
  value of a hit calculated from u/v segments
  compared to the x value of the x segment show
  that most of the detectors are working as
  expected
• With detectors integrated in readout, focus turns
  to trigger

11
2004 Fall Shutdown Work

• Minor repairs
• Replace veto counters (minor rad damage) and veto
  PMT'ssurvey
• Test spares in situ
• Camera repairs
• Survey before and after separator alignment
  changes
• Grounding studies
• Trigger commissioning
• FPD_LM commissioning
• Automatic pot insertion tests

Shutdown list is much shorter than last years!
Since access is restricted, a reliable robust
detector,electronics and pot motion system are
essential
12
Current Diffractive Triggers
Jet Gap(s) 15 GeV jet 1 or 2 gaps 2 gap
trigger has low prescale up to intermediate
lums 45 GeV jet 1 or 2 gaps prescale of 2 for
single gap up to 60E30, double gap unprescaled at
all lum J/?? Gap(s) 2 low pT muons1 or 2
gaps unprescaled at all luminosity
These triggers are being used to search for
exclusive dijets and exclusive ?c (among other
things), a key step towards validating
diffractive Higgs models. No results for public
display yet.
13
FPD Trigger and Readout
14
Trigger Team

• Andrew Brandt (UTA prof Trigger
  Logic/List/Oversight)
• Duncan Brown (UTA post-doc Trigger
  Implementation)
• Mario Vaz (UFRJ eng/phys FPD DFE equations/TM
  firmware)
• Wagner Carvalho (UERJ prof DFE equations/test
  vectors)
• Ricardo Ramirez (UTA EE M.S. FPD/DFE Interface)
• Tom Fitzpatrick (FNAL EE FPD/DFE Interface/DFE
  Timing)
• Brian Cox, Scott Kolya, Marc Kelly (Manchester
  FPD_LM)
• Carlos Avila, Luis Mendoza (Los Andes
  Stand-alone trigger)

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Trigger Manager Inputs

• FPD_LM
• Information on which detectors are hit and
  halo
• 2) LM pass through 16 LM and/or terms
• includes GapN GapS GAPSN SI etc.
• (much of this info is available through a
  different path)
• DFE information from scintillating fiber
  detectors,
• forseen to give ?, t now using segment
  information, multiplicity

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FPD-LM

• TDC Details
• Step I TDC in readout
• 3 TDC boards for FPD compared to 6 LM boards
• 1 board consists of Px1, and Ax1 where
  xUp,Down, In,
• Out pots (first quadrupole castle on
  either side of IP)
• 2 board consists of Px2, and Ax2
• (second quadrupole castle)
• 2 dipoles 4 veto counter signals
• Step II Add halo bit information to TDCs (almost
  finished by
• Man. guys during shutdown)
• Step III Pass bit info to vertex board (and then
  to TM)
• and add scalar info for pot insertion
  (January?)

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2004 Trigger Strategy

• Input information
• Currently no global run trigger capability
• LM Vertex board is delayed (just received)
• DFE boards and TM work and ready to be
  commissioned
• Main background not from pileup (multiple
  interactions) but from
• halo spray
• Strategy
• Instead of calculating bins of ? and t, use
  fiber hit patterns to
• demand 2 or 3 out of 3 planes of each
  detector have valid hits.
• Replaces trigger scintillator, simpler algo
• Use multiplicity cut to reject halo spray, code
  several multiplicity
• levels
• NOTE fiber ADC threshold must be high enough to
  avoid noise, low
• enough to retain efficiency and allow
  vetoing of halo
• One advantage is pot positions not needed at
  trigger level

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Interim Trigger Plan

• Proceed with DFE/TM debugging during shutdown
  hardware
• and firmware successfully tested, aiming
  for next major global
• trigger list in spring
• Since current FPD commissioning is special run
  intensive and
• new elastic triggers with adjacent
  spectrometer veto have rates
• around 1 Hz, we proposed adding an elastic
  trigger to first
• post-shutdown global trigger list
• This will only take one exposure group and allow
• us to obtain good elastic sample at lums
  lt45E30
• accepted by trigger board, will be
  operational in December

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FPD Trigger List
Tentative L1 FPD V14 trigger list (early 2005)
1) elastic (diag opposite spectrometers)
GAPSN 2) soft diffraction (single
spectrometers)GAPS or GAPN 3) overconstrained
track (pbar in quadrupole dipole
spectrometers)GAPN 4) double pom (up-up, dn-dn
etc.)GAPSN if needed 5) Jet FPD Track (DIFFQ
or DIFFD) GAPS or GAPN if needed 6) EM FPD
track GAP (if needed) 7) CFT Track(1.5) FPD
track GAP 8) Muon FPD track GAP
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Special Run Trigger
In-time hits in AU-PD detectors, no early time
hits, or LM or veto counter hits
Current NIM logic allows us to form several
elastic and diffractive triggers for special
runs using trigger scintillators (in parallel
information from scintillators is sent to TDCs
for commissioning FPD_LM system, and CAMAC
scalars), veto counters, and LM. Can trivially
switch from elastic to double pomeron (Aup-Pup
for example)
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Elastic Scattering

• Elastic scattering ? 0 (no momentum lost by
  beam particle)

• Quadrupole acceptance
• t gt 0.8 GeV2 (requires sufficient scattering
  angle to leave beam envelope)
• all ? (no longitudinal momentum loss necessary)

• Measure dN/dt for elastic scattering using early
  stand-alone FPD data

• antiproton side
• quadrupole up spectrometer
• trigger only

• proton side
• quadrupole down spectrometer
• full detector read-out

veto on LM and VETO counters, early time hits
(halo tracks)
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dN/dT Result of the week
http//www.fnal.gov/pub/today/archive_2004/today04
-03-18.html
Tremendous work especially by the Jorges to
obtain the preliminary dN/dT measurement.
Congrats again to Dr. Molina for first FPD PhD!
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Separator plates
Fall 2003 shutdown survey data (points AB) made
available by accelerator in April show offsets of
up to 0.7 cm! Required rewriting of MC to
separate separators, reanalysis of acceptance.
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The acceptance for the PD spectrometer
Before sep correction
After sep correction
Much better high-t acceptance (previously high-t
data thought to be halo)
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Elastic Status

• Re-evaluating acceptance and backgrounds based
  on
• new alignment, also studying AU-PD correlations
  
• Will decide soon if data is sufficiently well
  understood to
• publish
• Silver lining nearly 100 of effort directly
  transferable to
• new analyses

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FPD Dipole Jet Data
WORK IN PROGRESS
pbar
beam
x
p halo
y
(0,0)
D0
pbar halo
D2
D1

• Trigger one jet with pT gt 25 GeV and Gap on North
  (pbar side)
• Read out using AFE (Analog Front End) board FPD
  info extracted from raw data

inclusive
jet pT
tagged
jet ?f
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Dipole TDC Resolution
p
D2 TDC
p halo from previous bunch

• Can see bunch structure of both proton and
  antiproton beam
• Can reject proton halo at dipoles using TDC
  timing

D1 TDC
Timing is important
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Software Status

• L1 Firmware in good shape
• L3 FPD tracking tools and single interaction
  tools included in latest L3 release
• Offline reconstruction modified to run with
  standard DØ reconstruction program or in
  standalone mode
• Online examine programs incorporated in standard
  shifts
• Alignment and calibration routines being refined
• MC and Analysis software well-developed

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Lessons Learned

• Bigger project than you (I) might think more
  manpower, time, cost, CABLES
• Need a sufficient budget and some level of
  priority (Beyond the Baseline Syndrome)
• Using other peoples electronics is risky (minor
  adaptations often arent, make sure
• their schedule is much earlier than yours)
• Early integration (softwarehardware) is
  essential
• Good contacts in the Accelerator Division are
  crucial
• Halo not well-understood (mokhov did simulations,
  but), collimators not optimized,
• using bpms as found not so gooddo you know how
  to get bpms into data stream, etc.
• Commissioning phase long and personnel
  intensive, must have sufficient physicists and
  engineers on-site (lack of brazil travel funds
  really hurt us)
• Grounding issues (long cables in tunnel plugged
  into detector might cause problemsactual or
  perceived)
• Elastics for alignment critical, every store if
  possible
• Splicing fibers is painful
• Late trigger -gt late calibration sample
• Need more access than you might think

Not to mention software effort track
reconstruction, Monte Carlo database, online, etc.
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Diffractive Z
Event Selection Z?µµ- Events from 2003 data
sample Two good (PT gt 15GeV) oppositely charged
muons (at least one isolated), cosmic ray
rejection
Demand Activity North and South
Forward Gap (North or South)
Tamsin Edwards (Manchester) thesis work,
expected to be completed in next couple months
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Outlook and Plans

• Finish Level 1 Trigger Commissioning
• Continue routine data collection, add new
  triggersnew data
• samples
• Emphasis on physics/publishing mature results
  and
• obtaining new preliminary results
• Plan a special low-t (0.1-1) run soon, get your
  predictions
• of if/where the dip(s) will be for
  SD,DPEElastic
• Accelerator start-up going well (too well!)
  indications that
• halo background reduced