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Search for New Particles Which Decay to WZ 0

Search for New Particles Which Decay to WZ 0. Chris Battle & David Toback Texas A&M Henry Frisch University of Chicago for the CDF Collaboration. Outline. Theory Signature Fermilab & The CDF Detector Backgrounds & What Signal Would Look Like The Data Results Conclusions.

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Search for New Particles Which Decay to WZ 0

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  1. Search for New Particles Which Decay to WZ0 Chris Battle & David Toback Texas A&M Henry Frisch University of Chicago for the CDF Collaboration

  2. Outline • Theory • Signature • Fermilab & The CDF Detector • Backgrounds & What Signal Would Look Like • The Data • Results • Conclusions

  3. X WZ0 evjj • We want to search for new physics in a model independent manner • Many models predict new particles which decay via X WZ0 • W’  WZ0 ; Heavy version of Standard Model W • WR  WZ0 ; Right-handed version of Standard Model W • Technicolor Rho: rT WZ0

  4. Feynman Diagram

  5. Searching for the WZ0 Signature • Identify the W via the decay to electron and neutrino • Identify the Z0 via the decay to quark anti-quark which can be identified as “jets” • Search for new X particles at different masses and widths

  6. CDF Detector at Fermilab • Proton Anti- Proton Collisions at center of mass energy = 1.8 TeV • Approximately 3*1012 collisions studied (100 pb-1) in Run 1

  7. Standard Model Backgrounds • W+jets ( W  eν, W τν  eννν ) • Non W+jets • tt  WWbb  eνjj • bt  Wbb  eνjj • WW  eνjj • WZ0  eνjj • Z0 ( ee) + jets; one electron lost fakes ν • Z0 (ττ) + jets; one τ  e, one τ lost • Detector Malfunctions (Fake e and ν)

  8. Looking for Signal Events W+dijet mass bump Dijet mass bump

  9. What signal would look like

  10. Look for Mass Resonances in Data Dijet mass outside Z0 mass region:Control Sample Dijet mass inside Z0 mass region; Signal Region • Data outside Z0 mass region is well modeled. • No evidence for resonant WZ0 production.

  11. Set Cross Section Limits vs.Width • Example New Particle: Heavy Version of W, called W’ • 95% C.L. upper limits on the cross section vs. W’ width

  12. Limits on Mixing Factor vs. W’ Mass • Any new W’ would have to mix with Standard Model W • 95% C.L. exclusion region for W-W’ mixing factor vs. W’ mass

  13. Conclusions • No evidence forXWZ0 using the enjjdecay channel • Limits as a function of new particle mass • Limits as a function of new particle width • Most comprehensive limits on direct W’ WZ0 • Paper submitted to Phys. Rev. Lett. • hep-ex/0108004

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