Non-Prompt Tracks with the SiD Baseline Detector
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Non-Prompt Tracks with the SiD Baseline Detector. ALCPG07 FNAL Oct 22 – 26 2007 Bruce Schumm Santa Cruz Institute for Particle Physics. Many have contributed…. SLAC: Tim Nelson. Kansas State: Dima Onoprienko, Eckard von Toerne.

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Non-Prompt Tracks with the SiD Baseline Detector

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Non prompt tracks with the sid baseline detector

Non-Prompt Tracks with the SiD Baseline Detector

ALCPG07 FNAL

Oct 22 – 26 2007

Bruce Schumm

Santa Cruz Institute for Particle Physics


Non prompt tracks with the sid baseline detector

Many have contributed…

SLAC: Tim Nelson

Kansas State: Dima Onoprienko, Eckard von Toerne

Santa Cruz: Chris Betancourt, Chris Meyer, Tyler Rice, Lori Stevens, Bruce Schumm, Eric Wallace


Non prompt tracks with the sid baseline detector

In all its glory:

The SiD Tracker


Non prompt tracks with the sid baseline detector

“Inside-Out” Tracking requires 4 VXD layers

For e+e- qq, 5% of charged tracks originate outside of rorg = 2cm

“Cheat” these particles and their hits away (remove them from the banks). How well can we do on remaining “non-prompt” tracks?


Non prompt tracks with the sid baseline detector

Initial Tool: Axial Barrel Track Finder (ABTF)

Originally written by Tim Nelson to find tracks when VXD is tired or sick.

Finds tracks in 5-layer central tracker by extending three-hit seeds inward.

Optimized for non-prompt tracks (relax IP constraint, add a few tricks) by UCSC students.

UCSC students also added capability to use modular z information


Non prompt tracks with the sid baseline detector

1cm

5cm

10cm

30cm

1cm

5cm

10cm

30cm

Apply to qq events at Z Pole and at Ecm = 500 GeV (require at least 4 hits; all fakes are 4-hit)


Non prompt tracks with the sid baseline detector

Kansas State’s “Garfield” Algorithm

Extrapolates calorimeter “stubs” into tracker, attaching hits as appropriate

Adapted by UCSC students to run as third-pass tracker, after “cheating” and ABTF

Goal: improve efficiency and/or clean up 4-hit tracks and, if we can, reconstruct the 3-hit tracks.


Non prompt tracks with the sid baseline detector

Start with Z-Pole Events

ABTF 4-hit tracks already fairly pure; can Garfield help with leftovers?


Non prompt tracks with the sid baseline detector

Garfield gets a few more. But what about3-hit tracks?


Non prompt tracks with the sid baseline detector

Not so exciting.

Can we reliably reconstruct tracks that originate outside the second tracking layer?


Non prompt tracks with the sid baseline detector

Seeds-to-Stubs Program

Instead, UCSC students proposed matching precise three-hit tracker seeds to Garfield stubs

  • Helix – Stub Matching (optimized for Z  qq)

  • Base Difference < 2 mm

  • Phi Difference < 100 milliradians

  • Curvature Ratio ( (seed - stub)/ seed ) < 10

e.g.: Position-matching for isolated muons (mm)


Non prompt tracks with the sid baseline detector

Seed-to-Stubs Performance; Z  qq

  • Of a total of 20 3-hit particles:

  • 12 were reconstructed as 3-hit tracks, with only 4 fakes

  • Two additional 4-hit particles were found

  • BUT: Performance vastly worse for e+e-  qq at Ecm = 500 GeV. Could optimize for this type of event, but do we want to?

  •  Algorithm tuning dependent on signature under exploration


Non prompt tracks with the sid baseline detector

Next Steps: GSMB?

With Jonathan’s help, will generate meta-stable e+e-  stau+ stau- with stau+  ++ gravitino

Signature will be stiff charged track with kink (1-prong tau) or star (3-prong tau) in midst of tracker

Challenge will be to reconstruct kink again SM background of e+e-  +-

We’ve just started on this.


Non prompt tracks with the sid baseline detector

Conclusions

In the abstract, four-hit tracks (Rorg < 46 cm, compared to Rmax = 125 cm) seem possible with tracker + cal assist

Three-hit tracks (Rorg < 72 cm) very scenario-dependent, so trying to look at meaningful signature (GSMB)… what else?

Use these signatures to pin down value of z segmentation

What about detector concepts other than SiD?

Note: Much of this work done with junior and senior UG physics majors.


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