Diffractive Triggers

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Diffractive Triggers
Andrew Brandt, U. Texas at Arlington
FPD Workshop March 29, 2004 UERJ, Brazil
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Trigger Strategy I

• Write out FPD, LM for every DØ event (may need to
  strip LM info
• from Raw data?)
• -cross section determined using standard
  methods x fraction
• that are diffractive corrected for
  acceptanceefficiency
• 2) Trigger on events that would not get written
  otherwise
• (Ex. single diffractive, elastic, double
  pomeron)
• using FPD track AND/OR terms, sometimes
  combined
• with gaps (veto on LM N or S)
• -high rate processes, cross sections will
  be measured in special
• run at some point (along with total cross
  section?)
• -these triggers will be in global list (or
  2nd global run) to measure ? and t
• distributions, also be used as monitors and
  for alignment,
• calibration, and efficiency studies
• -double pomeron lower rate, will require
  extra thought for cross
• section, may be able to tie to elastics, or
  work backwards
• from double pomeron object triggers

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Trigger Strategy II
3) Trigger on events that would otherwise be
too heavily prescaled (Ex. Jets, J/?, and
then add gap(s) and/or track(s)) -cross
sections determined using object trigger that
does not have diffractive conditions and
then bootstrapping
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GapJet Triggers
JT_15TT_GAPN or S CJT(2,3)GAP L3(1,15)
Prescaled, currently .3-.4 Hz each Llt40E30
lt.1Hz at 40 E30 e80-l40-n30? JT_15TT_GAPSN
CJT(2,3)GAPS L3(1,15) Currently unprescaled
0.6 Hz at 40E30 prescaled (although natural
prescale from double gap should take
hold) JT_45TT_GAPN or S CJT(2,5)GAP L3(1,45)
Currently prescaled by 2 at 40E30 .08 Hz each
would like to keep unprescaled at least to 60E30
(like highest inclusive ET trigger). Also will
have natural SI prescale JT_45TT_GAPSN
CJT(2,5)GAPS L3(1,45) Unprescaled at all
luminosity 0.03 at 40E30 Also have 3
zero-biasgap triggers
These triggers are used for single diffractive
and double pomeron jet physics (Gaps and FPD).
Needs more people looking at data.
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J/?? Gaps
J/?? Gap 2MT1_2TRK_GAPN 2MT1_C_2L2L_2TRK
ALMNorthv 2MT1_2TRK_GAPS 2MT1_C_2L2L_2TRK
ALMSouthv Before Sep. shutdown prescale of 4
at 30E30, 200 at 40E30 (prescale now
lowered) Unprescaled rate .25 Hz _at_20E30 .5
Hz_at_40E30 e80-l60-n40 would be good Could be
unprescaled at all lum, when low PT track match
works J/?? Gaps 2MT1_2TRK_GAPSN
2MT1_C_2L2L_2TRK ALMSouthvALMNorthv lt.01 Hz
at 20E30 lt.04 at 80E30 should be unprescaled at
all luminosity These triggers are being used to
search for exclusive J/?? and ?C , a key
step towards validating diffractive Higgs models
No one has looked at this data yet!!!
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FPD DAQ
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FPD L1 Trigger

• Modelled after CTT (central fiber tracker
  trigger) but with fiber detectors read out by
  multi-anode phototubes (MAPMTs) instead of
  VLPCs
• Requires a transition board (TPP) to shape
  signals and discard excess charge for use with
  AFEs (Analog Front End boards) which receive
  signals, record analog values, and discriminate
• DFE (Digital Front End boards) receive digital
  signals from AFEs and apply tracking firmware to
  select potential good events and remove spray
  events
• LM TDC boards used to perform timing from hits in
  scintillators from the Luminosity Monitor
  sub-detector as well as the FPD trigger
  scintillators
• FPD timing and LM information will feed into FPD
  trigger manager (TM)
• along with DFE information to form FPD AND/OR
  terms

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FPD_LM
Includes 3 TDC boards for timing and one VTX
board which sends info to trigger manager, James
will update status
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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.
• (is anyone in LM group doing this) mostly
  can get this info separately
• DFE information from scintillating fiber
  detectors,
• forseen to give ?, t now using segment
  information, multiplicity

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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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Previous Plan for FPD Triggers

• The FPD Trigger Manager allows cuts on ?1-?p/p
  and t, and
• also incorporates information from the
  trigger scintillator via
• the LM boards.
• A track is defined as two detector hits in any
  spectrometer with
• a valid x and t, a trigger scint. confirm, and
  no halo veto set.
• AND-OR term definitions (13 used of 16 allowed)
• RTK track in any spectrometer, (D veto on
  halo)
• RPT proton track RAT anti-proton track
• RTK(1) x gt 0.99, all t
• RTK(2) 0.99 gt x gt 0.9 all t
• RTK(3) x gt 0.9 all t, no halo veto
• RTK(4) x gt 0.9, tgt1 GeV2
• RTK(5) x gt 0.9, all t
• REL Elastic (diagonally opposite p and )
• ROV Overconstrained track (DQ proton tracks)
• REL(1) x gt 0.99, all t REL(2) x gt
  0.99, t gt 1 GeV2
• ROV(1) x gt 0.90, all t ROV(2) x gt
  0.90, t gt 1 GeV2)

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New Trigger Plan

• Input information
• Currently no global run trigger capability
• Vertex board is delayed
• DFE boards work and TM ready to be commissioned
• Main background not from pileup (multiple
  interactions) but from halo spray
• New strategy
• Instead of calculating bin 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
• Need to settle on bit pattern to proceed with TM
  logic
• Measure efficiency with jet triggers, scint
  triggers from special runs

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Exposure Groups

• For normalization purposes each trigger is
  assigned an exposure group
• and live time is measured for that
  groupdifferent beam conditions require
• different groups
• Only 8 exposure groups (7 used), we have more
  combos so must
• operate outside exposure groupsnew value
  NOLUM
• If this is not changed we cannot run in global
  run
• Another issue is dynamic dowloading, which allows
  multiple global runs
• This would allow us to take elastic or other
  monitoring data in separate
• global run, so as to avoid general reco
  streaming and other issues with this
• Once TM is ready we are restricted to dedicated
  special runs until these
• other issues are resolved

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TM Algorithm
DFE will pass word for each spectrometer (Marios
talk) indicating coincidence of two detectors
(loose track and tight track, for example) At TM
we would form terms DIFFany spectrometer
track DIFFQany quadrupole spectrometer track
(could be false if gt1 or 2 on A or P
side) DIFFDdipole track ELASAU-PD or AD-PU or
AI-PO or AO-PI DPOMAU-(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) OVERAU-DI or AD-DI or
AO-DI or AI-DI (over-constrained track for
alignment)
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FPD Trigger List
Tentative L1 FPD trigger list. V13.x/V14
(April?) 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? 7) TTK(1,?) FPD track
GAP? 8) MU(1,x) FPD track GAP? Monitors may
be necessary, will need to study with
special runs. Also rates are unknown. If 4
(dpom) it is not low enough to run unprescaled we
would need to repeat 5-8 with two FPD
tracks. Possibly 1-3any monitors are best done
in a separate global run since they will not need
general farm reconstruction.
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Trigger Work
Short term trigger work DFE algorithms Mario,
Wagner Data analysis inputs from special runs
Molina, Mike, James, Renata DFE firmware
Ricardo, Daniel CTS tests Daniel DFE
examine? TM Daniel, Mario MC? Trigsim Wagner
Trigger database? L2 Gap ? L3 SI, Gap,
PLtot, FPDreco?
With detectors in readout, next key is maximizing
useful data sample getting L1 trigger online is
vital to FPD physics success