(Very) Preliminary Look at Gap Triggers

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(Very) Preliminary Look at Gap Triggers

• Andrew Brandt (analysis by Michael Strang)
• University of Texas at Arlington

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Gap Triggers

• There are several dedicated gap triggers in the
  Global DØ trigger list (Gap triggers first added
  in V7.4, reached current form in V8.2 after
  problems with CJT(3).
• JT_25TT_Gap CJT(2,5) L3JET(1,25)
• JT_25TT Requires 2 calorimeter jet towers at
  level 1 with ET above 5 GeV. At Level 3, a jet
  above 25 GeV with simple cone algorithm
• Gap Can be GAPN (-h, pbar-side), GAPS (h,
  Pside), GAPSN (both) or NG (no gap required)
• Starting to look at data to determine what Run II
  gaps look like (preliminary analysis on special
  run failed due to corrupted cal chunk)
• Also have zero_bias_Gap triggers for this study
• Mike Strang (diffractive jets) and Tamsin Edwards
  (double pomeron) and Pavel Demine working on
  defining a rapidity gap for RunII
• Compare diffractive jets to inclusive jets
• From Run I, expect Gap events to be quieter (less
  energy in forward region), with fewer and
  narrower jets than inclusive sample

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North vs. South Rates

• We have observed a difference in rate between
  GapN and GapS (higher) at Level 1. For trigger
  list 8.2
• (note cross sections not Begel-approved)
• L1(mb) L3(mb) prescale
• NG 10.0 3.57 220
• GapN 0.07 0.03 2
• GapS 0.70 0.25 8
• GapSN 0.01 0.01 1
• Would expect GapS and GapN to be equivalent, GapN
  appears closer to expectations, needs to be
  studied

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Data Selection

• Run 165008 (V8.3), reconstructed with p11.12.01
  4 hours at low (10e30) luminosity
• Applied standard event quality cuts
• pvtx lt 50. cm
• nvtx 1 for now
• Esum (cells gt 100 MeV) lt 2 TeV
• Events with 1 jet
• mET lt 0.7 jet.pt0
• Applied standard jet quality cuts and looked at
  jets gt 15 GeV
• 0.05 lt EMF lt 0.95
• CHF lt 0.4
• HotF lt 10.
• n90 gt 1.
• f90 lt -.05 CHF 0.8 where f90 n90 / nitm

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Cal Energy Comparison
GapS
?E ?gt2.5 (S)
?E ?lt-2.5 (N)
GapS
?E ?lt-2.5 (N)
?E ?gt2.5 (S)
GapN
GapN
Energy correlations as expected for GapN, but
GapS is contaminated
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NG energy vs. opposite side
NG
NG
GapN
GapS
Good gap events (GapN) have lower energy on
non-gap side than NG
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Leading Jet ET
NG
GapN
GapS
GapSN
Jets have similar ET distributions
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NJets (GapN vs. NG ET gt 15 GeV)
Gap-like events have less jets
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Jet Width (GapN vs. NG)
NG
GAPN
Gap-like events have narrower jets
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Summary

• Gap triggers are providing useful data, but GapS
  term is contaminated by large fraction of non-Gap
  events.
• - Could be due to timing of GapS and/or term
  (most likely)
• - Could be due to inefficiency of LM counters
  on South side
• Further study required (quick look by Rich
  inconclusive
• need time from Begel)
• Look at Zero Bias data to define gap (set
  thresholds)
• Move to more recent data, large stats
• Request lower prescale on JT_25TT_GapN trigger,
  balanced
• by higher prescale on GapS. Will be using
  GapN trigger for
• FPD AFE commissioning