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Searches for a Dark Matter Candidate in Particle Physics Experiments at the Fermilab Tevatron

Searches for a Dark Matter Candidate in Particle Physics Experiments at the Fermilab Tevatron. Paul Geffert , Max Goncharov, Eunsin Lee, Rishi Patel*, David Toback, Peter Wagner, and Slava Krutelyov** for the CDF Collaboration Texas A&M University New York University*

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Searches for a Dark Matter Candidate in Particle Physics Experiments at the Fermilab Tevatron

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  1. Searches for a Dark Matter Candidate in Particle Physics Experiments at the Fermilab Tevatron Paul Geffert, Max Goncharov, Eunsin Lee, Rishi Patel*, David Toback, Peter Wagner, and Slava Krutelyov** for the CDF Collaboration Texas A&M University New York University* University of California at Santa Barbara** Paul Geffert Texas APS 2007

  2. Outline • Dark matter • Supersymmetry and a dark matter candidate • Photon timing • The analysis and results • Future Improvements and Prospects • Conclusion Analysis Published in Phys. Rev. Lett. 99121801 (2007) Paul Geffert Texas APS 2007

  3. DarkMatter • What is dark matter? • Does not interact with photons (dark) • Has mass and interacts gravitationally • Could be an undiscovered particle Large fraction of the energy in the universe Paul Geffert Texas APS 2007

  4. Cold Dark Matter is favored for large scale galaxy formation • Warm Dark Matter is favored for subgalactic scale formation • Most searches focus on Cold Dark Matter, but we search for Warm Dark Matter because we have a powerful new search technique “Cold” Dark Matter vs. “Warm” Dark Matter Warm “Small Mass” ~1 keV Cold “Large Mass” ~100 GeV Paul Geffert Texas APS 2007

  5. g ~ G 4 neutralinos ci 2 charginos G c0i Supersymmetry • Supersymmetry is a model of particle physics that predicts new particles • If this theory is correct, one of these new particles could be the dark matter • Our warm dark matter candidate is a light gravitino, , the supersymmetric partner of the as yet undiscovered graviton For experts, a detailed discussion of GMSB Supersymmetry is Phys. Rev. D 58, 075005 (1998) Paul Geffert Texas APS 2007

  6. Supersymmetry and Dark Matter • In our model all supersymmetric particles decay into the lightest neutralino, , in the very early universe • The is long-lived (nanoseconds) and thus stable on the time scale of Inflation. At later times it decays via • The is the lightest supersymmetric particle and will not decay and thus could be dark matter • If it has a mass in the keV range, it is a good warm dark matter candidate Paul Geffert Texas APS 2007

  7. EM Calorimeter: Photon timing + 4-momentum Tevatron at Fermilab :Collider Detector at Fermilab (CDF) Surround the collision point with a huge detector CDF :To study the collisions The Tevatron (accelerator) :to produce high energy collisions Paul Geffert Texas APS 2007

  8. Neutralino Decays • Neutralinos can be produced in pairs in the Tevatron and decay(~100%) via • Nanosecond lifetime (long-lived) ’s would travel macroscopic distances in the detector before decaying Travel before decaying Escape the detector Can be detected : “Delayed” photons Paul Geffert Texas APS 2007

  9. Photons from Neutralino decays • SM photons always travel directly from the collision point to the detector with speed c • Neutralinos travel away from the collision point and then decay • The photon arrives at the detector later than expected, in other words “delayed” Photon Timing (EMTiming) Paul Geffert Texas APS 2007

  10. Searching for a “Delayed” Photon 2 candidate events in the signal region Expect 1.3±0.7 events from backgrounds Paul Geffert Texas APS 2007 PRL 99121801 (2007)

  11. Exclude Some of the Parameter Space No evidence for long-lived neutralinos Our result is the world’s best sensitivity! Neutralino Lifetime (ns) Previous Sensitivity Excluded Neutralino Mass (GeV) Paul Geffert Texas APS 2007 PRL 99121801 (2007)

  12. Future Prospects CDF Run II Preliminary Theoretically Favored Region Expected Exclusion with more data The Tevatron has already quadrupled the amount of data taken since this analysis. Expect a total of 20 times more. Current Exclusion Submitted to PRD Will have sensitivity to the theoretically favored region! Paul Geffert Texas APS 2007

  13. Improvements in Progress • Add more data to the current analysis • New data already in hand! • Improved analysis techniques • Complementary searches • Look for decay photons from both neutralinos • More sensitive to the low lifetime region Paul Geffert Texas APS 2007

  14. Conclusions • We have performed the world’s most sensitive search for long-lived particles that decay to a delayed photon and a dark matter candidate • New analyses in progress make the prospects for discovery very promising • With luck, we may be able to solve the cosmological mystery of dark matter Paul Geffert Texas APS 2007

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