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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. 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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  1. Non-Prompt Tracks with the SiD Baseline Detector ALCPG07 FNAL Oct 22 – 26 2007 Bruce Schumm Santa Cruz Institute for Particle Physics

  2. 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

  3. In all its glory: The SiD Tracker

  4. “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?

  5. 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

  6. 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)

  7. 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.

  8. Start with Z-Pole Events ABTF 4-hit tracks already fairly pure; can Garfield help with leftovers?

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

  10. Not so exciting. Can we reliably reconstruct tracks that originate outside the second tracking layer?

  11. 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)

  12. 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

  13. 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.

  14. 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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