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Supersymmetry (SUSY)

Supersymmetry (SUSY). Jennifer Temple December 1, 2005 QFT I. Outline. Introduction Standard Model Motivations for SUSY History of SUSY Theory SUSY Experiments Conclusion. The Standard Model (SM). Fermions: Quarks & leptons Half-integer unit spins (1/2, 3/2, …) Bosons:

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Supersymmetry (SUSY)

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  1. Supersymmetry(SUSY) Jennifer Temple December 1, 2005 QFT I

  2. Outline • Introduction • Standard Model • Motivations for SUSY • History of SUSY • Theory • SUSY Experiments • Conclusion

  3. The Standard Model (SM) • Fermions: • Quarks & leptons • Half-integer unit spins (1/2, 3/2, …) • Bosons: • Force mediators • Integer unit spins (0, 1, 2, …)

  4. The gauge hierarchy problem Characteristic energy of the SM: MW ~100 GeV Characteristic energy scale of gravity: MP ~ 1019 GeV Quantum gravity (?) SUSY algebra contains generator of space-time translations Quadratic divergence of the mass of scalar bosons Arbitrary parameters in the SM Electroweak symmetry breaking (EWSB) mechanism Why the SM is not enough…

  5. A (Very) Brief History of SUSY • First mathematically consistent formulation was made in the 1970’s by several independent groups • Part of superstring theory • Current collider studies set limits on the masses of SUSY particles

  6. So, what does SUSY actually say?

  7. Soft symmetry breaking SUSY is broken in nature, this is why we don’t observe it everyday This gives SUSY particles different masses Minimal Supersymmetic Model Electroweak symmetry breaking emerges naturally Unification R-Parity Some other features of SUSY

  8. SUSY Algebra • Supersymmetry is a symmetry that relates boson to fermion degrees of freedom. • The generators of supersymmetry are two component anticommuting spinors, satisfying:

  9. SUSY Lagrangian

  10. How would we detect SUSY experimentally? • Missing energy • SUSY particles must be produced in pairs and all but the lightest SUSY (LSUSY) particle will quickly decay into other SUSY particles or SM particles • LSUSY doesn’t interact with normal matter and so escapes the detector carrying off some energy • Jets

  11. SUSY Data

  12. Conclusion • Supersymmetry is a symmetry that relates boson to fermion degrees of freedom. It provides the basis for an extension of the SM description of particle interactions. • This is still an unproven theory and has a lot of opposition • Future experiments: • LHC @ CERN – 2007/8 • Linear Collider

  13. References • Haber, Howard E. and Kane, Gordon L., Is Nature Supersymmetric? • Schwarz, John H., String Theory, Supersymmetry, Unification, and All That, Reviews of Modern Physics, Vol. 71, No. 2, The American Physical Society, 1999 • Tata, Xerxes, What is Supersymmetry and How Do We Find It?, 1997 • Wagner, Carlos, SUSY Lectures I & II, Fermilab, June 2005 (http://www-cdf.fnal.gov/physics/lectures/) • Supersymmetry, Wikipedia

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