Update on CHAMP search

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 Sjostrands 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 stopquark
• 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 Sjostrands
  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, ptgt10 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 gt 4 GeV 40kHz (scaled up to 1E32)
• pT gt 8 GeV 6500 Hz
• pT gt 12 GeV 4300 Hz
• pT gt 20 GeV 2500 Hz
• pT gt 35 GeV 1650 Hz
• Also measured non-overlapping L1 rate for ptgt35
  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 pTgt10 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 Ptgt8 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).