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Forward Proton Detector Update. 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

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Forward proton detector update
Forward Proton Detector Update



  • 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



Andrew Brandt, UTA


























  • Personnel and Physics Goals

  • Hardware/Operations

  • Trigger

  • Elastic Analysis

  • Software

  • Outlook and Plans

UTA FPD Personnel/Resources

Andrew Brandt (UTA): FPD L3 Manager


Michael Strang (UTA GRA): data analysis

Duncan Brown (UTA post-doc): operations, trigger, diffractive physics (May 04--


Ricardo Ramirez (UTA EE GRA): trigger firmware

No longer employed by UTA:

Daniel Mendoza (UTA EE): readout and trigger commissioning

Funding DOE OJI ($81k), NSF MRI (NIU+UTA $125,000, equipment+GRA for 2 years through Aug. 05) , 6 months post-doc from UTA VP for research (one time seed money) {start-up, ARP finished}

Other FPD Senior Personnel


Gilvan Alves, general software (3 months Fermi)

Jorge Barreto, tracking (0)

Marcia Begalli, detector commissioning (6 months)

Jorge Molina, data analysis (3 months)

Maria Elena Pol, detector commissioning (4 months)

others with smaller DØ research fractions


Carlos Avila, alignment (3 months)

FNAL $200k support for Brazilian and Columbian visitors for 2004-2005

(FPD +Luminosity Monitor)

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

<100 W boson events in Run I, >100

tagged events expected in Run II

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

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 accident in 12/03 grounded TeV for 2 weeks, pots for 1 month.


  • Operations in 2004 have been routine, only occasional minor problems, much less than average sub-detector

  • Currently FPD expert shifters inserts pots and Captains removing pots and setting system to standby

  • 18 pots inserted every store when lum<45E30, note in 2003

  • we often only inserted dipole pots due to readout commishioning

  • 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

Detector hit resolutions
Detector Hit Resolutions

  • Starting in January 2004, all 18 detectors regularly inserted (dipoles since February 2003)

  • Commissioning underway on quadrupoles

  • 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

FPD Readout

Front View of PW08 (11/10/03)

2004 fall shutdown work
2004 Fall Shutdown Work


  • Repair P2I and A2O (light leak tests), move to one spectrometer

  • Investigate A1O first step in problems

  • Test spare multiplexor+control boards, spare PMT’s

  • Camera repairs

  • Survey before and after separator alignment changes

  • Ground searches+repairs

    In Progress

  • Investigate any cabling/mapping problems

  • Replace veto counters and veto PMT's+survey

  • Trigger commissioning

  • LM commissioning

  • Automatic pot insertion tests

Trigger team
Trigger Team

  • Andrew Brandt (Trigger Logic/List/Oversight)

  • Duncan Brown (Trigger Implementation)

  • Mario Vaz (FPD DFE equations/TM firmware)

  • Wagner Carvalho (DFE equations/test vectors)

  • Ricardo Ramirez (FPD/DFE Interface)

  • Tom Fitzpatrick (FPD/DFE Interface/DFE Timing)

  • Brian Cox, Dave Mercer, Scott Kolya (LM)

  • Carlos Avila, Luis Mendoza (Stand-alone trigger)

Current Diffractive Triggers

Jet +Gap(s):

JT_15TT_GAPN or S CJT(2,3)+GAP L3(1,15)

Prescaled, currently .3-.4 Hz each L<40E30; <.1Hz at 40 E30

JT_15TT_GAPSN CJT(2,3)+GAPS L3(1,15)

Currently unprescaled 0.6 Hz at 40E30; small prescale above

JT_45TT_GAPN or S CJT(2,5)+GAP L3(1,45)

Currently prescaled by 2 at 60E30 .08 Hz each

JT_45TT_GAPSN CJT(2,5)+GAPS L3(1,45)

Unprescaled at all luminosity 0.03 at 40E30

J/ +Gap(s)

2MT1_2TRK_GAPN = 2MT1_C_2L2L_2TRK + ALMNorth[v]

2MT1_2TRK_GAPS = 2MT1_C_2L2L_2TRK + ALMSouth[v]

2MT1_2TRK_GAPSN = 2MT1_C_2L2L_2TRK + ALMSouth[v]ALMNorth[v}

Unprescaled at all luminosity

These triggers are being used to search for exclusive J/ and C , a key step

towards validating diffractive Higgs models

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.

  • mostly can get this info separately

  • DFE information from scintillating fiber detectors,

  • forseen to give , t now using segment information, multiplicity





















  • 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 x=Up,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 TDC’s (shutdown)

  • Step III Pass bit info to vertex board (and then to TM)

  • and add scalar info (December?)

2004 Trigger Strategy

  • Input information:

  • Currently no global run trigger capability

  • LM Vertex board is delayed (may now be finished during shutdown)

  • 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 are hit. 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

  • Issues:

  • Setting ADC threshold, need special run (and analysis)

  • Dealing with noisy channels, variable means, could initially set threshold high,

  • later load in mean pattern, known hot channels

  • Measure efficiency with jet triggers, scint triggers from special runs

  • Exposure groups, triggers in global run or separate global run

Exposure Groups etc.

  • For normalization purposes each trigger is assigned an exposure group

  • and live time is measured for that group—different beam conditions require

  • different groups

  • Only 8 exposure groups (6 used), we have more combos so must

  • operate outside exposure groups—new value NOLUM

  • This is a trigger database change which was requested more than one

  • year ago and was hostage to internal Fermilab DØ/CD politics

  • Now estimated completion of DB work is January

  • Once FPD DFE/TM is ready we are mostly restricted to dedicated special

  • runs until database issue resolved

Interim Trigger Plan

  • Proceed with DFE/TM debugging during shutdown

  • 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 <45E30;

  • accepted by trigger board, will be operational in December

Trigger progress
Trigger Progress

  • DFE/TM chain tested by Duncan with help from Jamieson and Jeff Temple, works with simple test firmware. All hardware works.

  • Two versions of DFE firmware developed by Mario+Ricardo, being incorporated by Tom into standard DØ framework.

  • Early failures traced to delays between different inputs to DFE, Tom worked out solution similar to TM, which waits for all inputs before processing; Duncan just tested successfully.

    4. Ricardo is working on arbiter, which is necessary to add outputs from 3 spectrometers to form 96 bit DFE word sent to TM. He has produced a 3-chip testbench to simulate full DFE, simulations work, about to be tested on platform.

    5. Jeff +Mario produced first version of TM firmware, Duncan testing it this week.

V4 TM Algorithm

DFE will pass word for each spectrometer indicating coincidence of two detectors

tight track: exactly 1 hit with 3/3 fine segments in each detector

medium : >0 with 2/3 + <20 wide segement

loose: => 0 with 2/3 + <20 wide segement

At TM we form terms

DIFF=any spectrometer track

DIFFQ=any quadrupole spectrometer track (could be false if >1 or 2 on A or P side)

DIFFD=dipole track


DPOM=AU-(PU or PI or PO) or AD-(PD or PI or PO) or AI-(PU or PI or PD) or

AO-(PU or PD or PO)+DI -(PU or PD or PO or PI)

OVER=AU-DI or AD-DI or AO-DI or AI-DI (over-constrained track for alignment)

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) CJT(2,3) + FPD Track (DIFFQ or DIFFD) +GAPS or GAPN if needed

6) CEM(1,3) +FPD track +GAP (if needed)

7) TTK(1,1.5) +FPD track +GAP

8) MU(1,x) +FPD track +GAP

Rates are not yet well known. If 4 (dpom) it is not low enough to

run unprescaled we would need to repeat 5-8 with two FPD tracks.

Special Run Trigger



Halo Early Hits







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 TDC’s for

commissioning FPD_LM system, and CAMAC scalars), veto

counters, and LM. Can trivially switch from elastic to double

pomeron (Aup-Pup for example)

Elastic scattering
Elastic Scattering









  • Elastic scattering: ξ = 0 (no momentum lost by beam particle)

  • Quadrupole acceptance:

    • t > 0.8 GeV2 (requires sufficient scattering angle to leave beam envelope)

    • all ξ (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)

Dn dt result of the week
dN/dT Result of the week

Tremendous work especially by the Jorge’s to obtain the preliminary

dN/dT measurement. Congrats again to Dr. Molina for first FPD PhD!

Separator plates

Fall 2003 shutdown survey data (points A+B) made available by accelerator in April show offsets of up to 0.7 cm! Required rewriting of MC to separate separators,

reanalysis of acceptance.


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)

Elastic status
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


  • Silver lining: nearly 100% of effort directly transferable to

    new analyses

Software status
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 discussed in other talks

Outlook and plans
Outlook and Plans

  • Finish Level 1 Trigger Commissioning

  • Continue routine data collection, add new triggers=new data


  • Emphasis on physics/publishing mature results and

    obtaining new preliminary results

  • Plan to operate FPD through 2006 shutdown, perhaps

    periodic special runs after that

  • AB will ramp down involvement as commissioning phase finally draws to a close; continue in a consulting role only after mid-2006