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SUSY Dark Matter. Daniel Stolarski. Outline. What is (and isn’t) dark matter Why weak scale dark matter MSSM dark matter Digression: MSSM parameter space Gravitino LSP Ben will talk about “usual” scenario. What is (and isn’t) Dark Matter?. The majority of particles in our universe

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Daniel Stolarski


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    1. SUSY Dark Matter Daniel Stolarski Physics 290E Seminar 1/18

    2. Outline • What is (and isn’t) dark matter • Why weak scale dark matter • MSSM dark matter • Digression: MSSM parameter space • Gravitino LSP • Ben will talk about “usual” scenario Physics 290E Seminar 2/18

    3. What is (and isn’t) Dark Matter? • The majority of particles in our universe • Not charged under strong or EM forces • Must be cold (heavy) • Low interaction cross section Physics 290E Seminar 3/18

    4. WIMP Dark Matter • Assume WIMP starts out in thermal equilibrium • Eventually freezes out due to expansion of universe • With standard history can compute relic density today Physics 290E Seminar 4/18

    5. Relic Density Estimate DM number density Annihilation frequency Hubble constant Thermally averaged annihilation cross section Scale factor Reduced Planck Mass Physics 290E Seminar 5/18

    6. Cross section for top quark at Tevatron χ SM g g χ SM Mass of the Dark Matter Weak scale comes out miraculously! H. Murayama, arXiv:0704.2276 [hep-ph] Physics 290E Seminar 6/18

    7. R-parity makes LSP stable Must be neutral to be reasonable dark matter candidate Sneutrino? Most natural Ruled out by direct detection Neutralino Mixture of photino, Zino, Higgsino Generically allowed by direct detection expts. Gravitino Spin 3/2 partner of graviton Will never be directly detected Produced at LHC MSSM Dark Matter Physics 290E Seminar 7/18

    8. DIGRESSION: MSSM Parameters Physics 290E Seminar 8/18

    9. Constraints On Parameter Space • Flavor and CP violation experiments put strong constraints on parameter space • Neutron and electron EDMs Physics 290E Seminar 9/18

    10. SUSY theory will contain flavor universality Down to 15 new parameters Assume some kind of unification of forces and matter One gaugino mass m1/2 One matter mass m0 One trilinear term A Four parameters in Higgs sector Trade two for mZand tanβ Reproducing mSUGRA Physics 290E Seminar 10/18

    11. Instead of a flavor universality ansatz, can have a mechanism SM gauge interactions are flavor universal Mass proportional to gauge coupling Parameters: {F, M, N, tanβ} Gauge Mediated SUSY Breaking Physics 290E Seminar 11/18

    12. Back to Regularly Scheduled Dark Matter Program Physics 290E Seminar 12/18

    13. Gravitino LSP • mSUGRA always has neutralino LSP • Could be gravitino, especially in GMSB • Properties ; • Can use NLSP decay to tune relic density Next-to-lightest SUSY particle (NLSP) Physics 290E Seminar 13/18

    14. Must be cold (nonrelativistic at structure formation) For mN = 100 GeV, m3/2=1keV, lifetime = 40 ns For heavy gravitino, there is bound from BBN because of long lifetime Constraints on Gravitino F. Steffen, arXiv:hep-ph/0605306 Physics 290E Seminar 14/18

    15. Phenomenology controlled by next-to-lightest SUSY particle (NLSP) All events cascade to NLSP NLSP later decays to gravitino + SM particle Look for particles coming from random places in the detector Can be neutralino If lifetime ≤ 1 sec., NLSP can be charged or even colored Stau Stop Sneutrino Could give spectacular collider signatures if lifetime greater than time of flight LHC Signatures Physics 290E Seminar 15/18

    16. Charged “stable” sleptons are easy to see Measure momentum in tracker Measure β by time of flight to muon chamber Can discriminate for 0.6 ≤β ≤ 0.91 Produced in cascade decays with many leptons No missing energy can reconstruct full event Can measure mass of most low lying states Charged Stable Sleptons • S. Ambrosanio et. al., • arXiv:hep-ph/0010081 Physics 290E Seminar 16/18

    17. Long lived NLSP escapes main detector Want to measure NLSP lifetime and decays Look for SM particles coming in rock1 Build stopper detector outside main detector2 Signatures – Long Lived NLSP • arXiv:hep-ph/0508198 • arXiv:hep-ph/0612060 Physics 290E Seminar 17/18

    18. Conclusion • Standard mSUGRA scenario is an assumption • Only small regions of parameter space fit dark matter data • Nonstandard scenarios can be more interesting, not less well motivated • All this assumes WIMP scenario, but many other possibilities Physics 290E Seminar 18/18