Supersymmetry (SUSY)

1. Supersymmetry (SUSY) Kevin

2. Overview • Introduction of SUSY • MSSM • Current Research and Future Prospects

3. What is SUSY? • Supersymmetry is a generalization of the space-time symmetries of quantum field theory that transforms fermions into bosons and vice versa. • Possible that supersymmetry will ultimately explain the origin of the large hierarchy of evergy scales from the W and Z masses to the Planck scale. • It also provides a framework for the unification of particle physics and gravity which is governed by Planck scale. Mp=1019 Gev

4. Why SUSY? • Weakness of gravity relative to the other forces Plank scale: Mp= 1019 GeV Coupling constant: 1,1/137,10-6,10-39 Gauge hierarchy problem. • Supersymmetry allows the electromagnetic force, the weak force and the strong force—to be unified into one. • Supersymmetry solves the gauge hierarchy problem by introducing superpartners

5. Review of the forces

6. Unification of all the forces &Planck length.

7. Massive superpartners • The supersymmetric theory postulates that every particle we observe has a massive "shadow" particle partner.

8. SUPERPARTNERS

9. SUPERPARTNERS Superpartner names are derived from their Standard Model counterparts by appending the suffix "-ino" for supersymmetric fermions and adding the prefix "s-" for supersymmetric bosons. Symbolically, they are denotedby adding tildes (~) to the symbols for their Standard Model partners

10. Properties of superpartners

11. Region in the plane excluded by search at CDF LEP D0

12. LSP • LSP means the lightest supersymmetric particle.For most typical choices of model parameters, the lightest neutralino is the LSP. • The supersymmetric particles must be produced in pairs and they are unstable and decay quickly into lighter states---LSP. • LSP is absolutely stable if R-parity is conserved. • In order to be consistent with cosmological constraints, a stable LSP is almost certainly electrically and color neutral. • In order to better understand these, we need to know MSSM.

13. MSSM • The minimal supersymmetric extensionn of the Standard Model. • The unification of the three gauge couplings at an energy scale close to the Planck scale, which does not occur in the Standard Model, is seen to occur in the minimal supersymmetric extension of the Standard Model.

14. Structure of the MSSM • It consists of taking the Standard Model and adding the supersymmetric partners. • It contains two hypercharge Y=+1and –1 Higgs doublets,which is the minimal structure of the Higgs sector of an anomaly-free supersymmetric extension of Standard Model. • It requires two Higgs doublets to generate mass for both “up” –type and “down”-type quarks(and charged leptons) • All renormalizable supersymmetric interactions consistent with (global) B-L conservation are included. • The most general soft-supersymmetry-breaking terms are added.

15. Parameters for SM and MSSM • 19 free parameters for SM: 3 gauge couplings, 9 charged fermion masses, 4 mixing angles,Higgs VEV,Quartic couping(Mz),and QCD  parameter. • 124 Parameters for MSSM: 105 new. • Constrained MSSMs: mSUGRA (minimal supergravity) etc. They have less parameters.

16. R parity • As a consequence of B-L invariance, the MSSM possesses a multiplicative R-parity invariance, where R= (-1) 3(B-L)+2S for a particle of spin S. • All the ordinary Standard Model particles have even R parity and superpartners have odd R parity. • if R parity was conserved, starting from an initial state involving ordinary particles, it follows that superpartners must be produced in pairs and the LSP is absolutely stable.

17. CURRENT SEARCHES AND FUTURE PROSPECTS • Searching for superpartners in high- energy collider experiments. • Searching for supersymmetry are also underway in a variety of low-energy particle physics experiments. Although such experiments cannot produce superpartners, they may be sensitive to the effects of short-lived superpartners that may exist as a result of Heisenberg's uncertaintyprinciple. • In many supersymmetric theories, the lightest superpartner is stable and interacts weakly with ordinary matter. Such particles are natural candidates for dark matter, the mass responsible for the observed binding together galaxies and galaxy clusters, which has not yet been identified. Searches for dark matter are also, then, searches for superpartners, and many current and future dark matter detection experiments are sensitive to supersymmetric dark matter

18. CERN • The Large Hadron Collider : pp@ 7 TeV • The Large Electron Positron (LEP) e- e+ @ 200GeV

19. Fermi Lab • the Collider Detector at Fermilab (CDF), is searching for this escaping LSP

20. One possible way to produce smuons at LEP.

21. The background for smuon production

22. Selectron production

23. Gluinos production 4 jets + E

24. How winos and zinos might be produced?

25. Prediction for missing energy distribution

26. CDF Search for Squarks and Gluinos in MET 3jets