# Presentation: 707502

## Update on CHAMP search

- Bill Orejudos, LBNL
- Exotics Meeting
- Oct 19, 2001

## Outline

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

## 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.

## 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.

## 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.

##                       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

## Pt from Pythia

- stau

- stop

-           (generator level pT)

## 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.

## Reconstructed Pt

- Stau (OBSP matching)

- Stop (OBSP Matching)

## Isolation

- Number of tracks in 30 degree cone around CHAMP

- stau

- stop

## 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.

## 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).

## 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.

## 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

## 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.

## 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

## 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).