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Update on CHAMP search

Update on CHAMP search. Bill Orejudos, LBNL Exotics Meeting Oct 19, 2001. Outline. CHAMPS: CHA rged M assive (long-lived) P articles Work done since last talk (Aug 24) Addition of stops in cdfSim Some small tests for triggers. Stable Stops in cdfSim.

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Update on CHAMP search

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  1. Update on CHAMP search Bill Orejudos, LBNL Exotics Meeting Oct 19, 2001

  2. Outline • CHAMPS: CHArged Massive (long-lived) Particles • Work done since last talk (Aug 24) • Addition of stops in cdfSim • Some small tests for triggers

  3. Stable Stops in cdfSim • SUSY models exists in which a stable stau acts as the CHAMP • But, also SUSY models in which stable stop acts as the CHAMP • Have already introduced stable staus into cdfSim • All efficiency studies so far based on staus • Recently managed to get stable stops into cdfSim as well • Was it straightfoward? No. Is all work on this done? Absolutely not.

  4. Step 1: Pythia • Standard Pythia crashes when you force stop to be LSP. • Got code from T. Sjostrand to take care of stop fragmentation. Stan Thompson helped with the implementation • Need to turn master frag switch OFF, mstp(111)=0 • Then use Sjostrand’s function • The call pyexec seperately to do fragmentation for rest of the event.

  5. Sample output • The “stop hadron” is actually composed of 2 particles listed separately: the stop itself and the quark/antiquark • For convenience, in cdfSim I just look at the stop squark rather than the “stop+quark” • The stop hadron is assigned a non-standard stability code of 16.

  6. KS KF PX PY PZ E MASS 23 (~t_1)16 1000006 9 -141.034 -71.437 -104.218 274.658 198.951 24 (ubar)16 -2 9 0.000 0.000 0.000 0.000 0.000 25 (~t_1bar)16 -1000006 19 128.328 77.233 -270.066 367.448 199.121 26 (u)16 2 19 0.000 0.000 0.000 0.000 0.000 27 (string) 11 92 9 14.782 -6.119 863.678 867.517 79.930 28 K+ 1 321 27 -0.939 -0.543 -0.248 1.217 0.494 29 (Kbar0) 11 -311 27 0.372 0.120 0.648 0.906 0.498 30 (Delta-) 11 1114 27 0.289 -0.177 4.269 4.458 1.239 31 (rho0) 11 113 27 0.099 0.118 3.501 3.579 0.727 32 (Sigmabar+) 11 -3112 27 1.216 -0.324 18.877 18.957 1.197 33 K- 1 -321 27 0.048 -0.084 7.967 7.983 0.494 34 pi+ 1 211 27 3.997 -0.292 25.336 25.652 0.140

  7. Pt from Pythia (generator level pT) stop stau

  8. Step 2: cdfSim/Geant • Also need to repeat the steps taken to get stable staus into the simulation • Pdg code / cdf code correspondence (hepevt table in ParticleDB package) • Geant code / cdf code correspondence (CdfParticledatabase.cc in ParticleDB) • Declare particle to Geant (geant_i) • Additional step of modifying lunhep to deal with non-standard KS codes assigned in Sjostrand’s function. • Will work on getting all these mods put into standard software release next week.

  9. Reconstructed Pt Stau (OBSP matching) Stop (OBSP Matching)

  10. Isolation Number of tracks in 30 degree cone around CHAMP stop stau

  11. Trigger Efficiency • Use high-pt 2 track trigger • 2 XFT trks, pt>10 at L1 • Isolation, SVT trks at L2 • Check efficiency after L1 cuts (looked at XFT bits after running XFTSIM) • 200 GeV stable staus: 60% efficient • 200 GeV stable stops: 58% efficient • L1 efficiency essentially the same! • Eff. After isolation also essentially the same.

  12. 1 Track Trigger Rates • Measured L1 trk rates for different thresholds (total allowed is 40kHz): • pT > 4 GeV: 40kHz (scaled up to 1E32) • pT > 8 GeV: 6500 Hz • pT > 12 GeV: 4300 Hz • pT > 20 GeV: 2500 Hz • pT > 35 GeV: 1650 Hz • Also measured non-overlapping L1 rate for pt>35 GeV to be 600 Hz (takes overlap with B-phys 2 trk trigger and 6 track auto accept into account).

  13. 2 Track Trigger Rates • Estimated the high pt 2 track rate by looking at the XFT tracks offline • Require 2 XFT tracks with 4 layers and pT>10 GeV. • Get a L1 rate of about 40 Hz (scaled up to 1E32) • In my CDF note, estimated L1 rate from run 1 min bias data was about 40 Hz.

  14. First look at measured L2 rates • Recently, Alex ran some SVT tests for me! • Important because high pt 2 track trigger asks for SVT tracks to get rid of XFT fakes • Looked at Pt>8 GeV track trigger • L1 rate: 467 Hz • L2 rate: 12 Hz • L2 rate should be: 467Hz * 0.1-0.5 (SVT Eff) * 0.92 (4 SVX hits) *0.4 (Si coverage) * 0.75 (XFT non-fake) = 13-65 Hz

  15. Conclusion • Stable stops can now be generated, simulated • Preliminary tests indicate high Pt 2 track rate under control (at L1). • Runs with Tof data available – still waiting for necessary calibrations.

  16. Tools for analysis: TOF • Have done work to insure ToF code compatible with heavy, slow moving particle (for example, in T0 calculation). • Have analysis set up that uses the ToF methods • Tested with MC • Waiting for data

  17. Tools for analysis: dEdx • As discussed before, wrote class to access dEdx info • Methods to return truncated mean, vector of hits • Can get mean with, without online calibration • Recently added method to give truncated mean with the pathlength correction • Yesterday, updated online calibration code • Got rid of python script • Code now more reliable, faster – did a 40 point scan (each point a different value of injected charge) in just a few minutes).

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