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(Very) Preliminary Look at Gap Triggers

(Very) Preliminary Look at Gap Triggers. Andrew Brandt (analysis by Michael Strang) University of Texas at Arlington. P. X. I. P. J 2. Pbar. X. X. J 1. Gap Triggers.

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(Very) Preliminary Look at Gap Triggers

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  1. (Very) Preliminary Look at Gap Triggers Andrew Brandt (analysis by Michael Strang) University of Texas at Arlington P X I P J2 Pbar X X J1

  2. 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

  3. 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

  4. Data Selection • Run 165008 (V8.3), reconstructed with p11.12.01; 4 hours at low (~10e30) luminosity • Applied standard event quality cuts • |pvtx| < 50. cm • nvtx = 1 for now • Esum (cells > 100 MeV) < 2 TeV • Events with 1 jet: • mET < 0.7 * jet.pt[0] • Applied standard jet quality cuts and looked at jets > 15 GeV • 0.05 < EMF < 0.95 • CHF < 0.4 • HotF < 10. • n90 > 1. • f90 < -.05 * CHF + 0.8 where f90 = n90 / nitm

  5. Cal Energy Comparison E >2.5 (S) E <-2.5 (N) GapS GapS E <-2.5 (N) E >2.5 (S) GapN GapN Energy correlations as expected for GapN, but GapS is contaminated

  6. NG energy vs. opposite side E >2.5 (S) E <-2.5 (N) E >2.5 (S) E <-2.5 (N) NG NG GapN GapS Good gap events (GapN) have lower energy on non-gap side than NG

  7. Leading Jet ET NG GapN GapS GapSN Jets have similar ET distributions

  8. NJets (GapN vs. NG ET > 15 GeV) Gap-like events have less jets

  9. Jet Width (GapN vs. NG) NG GAPN Gap-like events have narrower jets

  10. 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

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