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SUSY studies at UCSC

SUSY studies at UCSC. Bruce Schumm UC Santa Cruz Cornell Linear Collider Workshop July 13-16, 2003. Participants. Sharon Gerbode , Heath Holguin, Paul Mooser, Adam Pearlstein, Bruce Schumm (all UCSC), with substantial help from Tim Barklow at SLAC.

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SUSY studies at UCSC

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  1. SUSY studies at UCSC Bruce Schumm UC Santa Cruz Cornell Linear Collider Workshop July 13-16, 2003

  2. Participants Sharon Gerbode, Heath Holguin, Paul Mooser, Adam Pearlstein, Bruce Schumm (all UCSC), with substantial help from Tim Barklow at SLAC Sharon, Heath, Paul, and Adam are upper-division physics majors at UCSC. Sharon just finished her senior thesis this year and is staying on a bit longer; other three are just getting started

  3. Motivation Resolution of forward tracking degrades in nominal tracker designs. SUSY endpoint measurements require high precision. Might there be information in the forward direction? Will our instrumentation be up to the task?

  4. selectrons LSP

  5. Right-handed selectrons at Ecm = 1 TeV

  6. Background Simulation I Making use of WHIZARD Monte Carlo package Some credits: • WHIZARD due to Wolfgang Kilian • Making use matrix elements from O’Mega program (Thorsten Ohl) • Implementation by Tim Barklow, SLAC Background processes characterized by final state (e.g. e+e-e+e- includes Z0 Z0 channel as well as nominal gg channel)

  7. Background Simulation II We have gotten started with eeee backgrounds e+ e+ e- g* e+ g* e- e-

  8. Background Simulation III The cross section for this process is effectively infinite • Must choose cut-offs which are guided by experi- mental constraints. This can be tricky, and there is a risk that a dom- inant background will go unmodelled N.B. Background simulations done by Tim Barklow

  9. Hard Cut-off Sample For this sample, a hard cutoff was applied to the invariant mass of any e+in/e+out e-in/e-out or final- state e+e- pair In the absence of any feedback, Tim chose a cut- off of

  10. e e g* e- * e+ g* Weiszacker-Williams Sample Complementary to hard cutoff sample Cross-section determined by integral over Cut of imposed on any eg pair

  11. Mmin Hard Cutoff W-W 10 GeV Un-simulated region Q2 10 GeV Idealized Background-Generation Phase Space Mmin is the least of the invariant masses of all final-state e+e- pairings

  12. SUSY-Inspired Cuts Look at distribution of backgrounds for SUSY-like events Define two detector regions |cosq| < 0.80 (100 mrad)  Tracking region (central!) ( - 20) mrad > q > 20 mrad pt >  Tagging region `SUSY event’ if and only if 1 electron and 1 positron in tracking region, no additional tracks in tagging region Note: We are doing analysis in central region for now as we continue to ramp up our group.

  13. e  < 20 mrad e * SUSY-Inspired Cuts II If neither beam particle in e+e-e+e- event makes it into the tagging region, the event can be confused with SUSY For such events, maximum pt carried by beam particles is ptmax = 2*Ebeam*tagmin = 20 GeV  Require ptmiss > 20 GeV for tracks in tracking region (DELPHI) Completely eliminates e+e-e+e- process up to radiative effects

  14. SPS1 Selectrons Results for 10 fb-1:

  15. Weiszacker-Williams Sample; 10 GeV cutoffs Qmin

  16. Weiszacker-Williams Sample; 10 GeV cutoffs Mmin

  17. Simulation Phase-space Question: Are events piling up against artificial kinematic cut-offs, particularly in Mmin?  Lower cut-offs to 4 GeV and se what happens! Mmin Hard Cutoff W-W 10 GeV 4 GeV Un-simulated region 4 GeV Q2 10 GeV

  18. Hard-cut sample; 4 GeV cutoffs Qmin

  19. Weiszacker-Williams sample; 4 GeV cutoffs Should cut off at 4 GeV? Qmin

  20. Weiszacker-Williams sample; 4 GeV cutoffs Mmin

  21. SPS1 Selectrons Again Results for 10 fb-1:

  22. Cunclusions, Outlook e+e-e+e- backgrounds seem adequately modeled (use samples with 4 GeV cut to be safe) WW samples should cut off at Q  4? Incorporate ee,  backgrounds (full SM whizdata files?) Start to push cos, p coverage Tracking specifications?

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