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Supersymmetry Basics: Lecture II

Supersymmetry Basics: Lecture II. J. Hewett. SSI 2012. J. Hewett. Implications of LHC Results. Implications of LHC Results. Soft SUSY Breaking Mechanisms. Spontaneous SUSY breaking ( vev w/ tree-level couplings) Requires a gauge extension to the MSSM

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Supersymmetry Basics: Lecture II

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  1. Supersymmetry Basics:Lecture II J. Hewett SSI 2012 J. Hewett

  2. Implications of LHC Results

  3. Implications of LHC Results

  4. Soft SUSY Breaking Mechanisms • Spontaneous SUSY breaking (vev w/ tree-level couplings) • Requires a gauge extension to the MSSM • Tends to yield unacceptably small sparticle masses Assume MSSM soft terms arise radiatively • SUSY breaking occurs in hidden sector which has little to none direct couplings to visible sector • SUSY breaking mediated through shared interactions Supersymmetry breaking origin (Hidden sector) MSSM (Visible sector)

  5. Gravity-Mediated SUSY Breaking • vev <F> in hidden sector breaks SUSY • Communicated to visible sector by gravitational interactions • msoft ~ <F>/MPl • msoft ~ 100 GeV if √<F> ~ 1010-11 GeV Supersymmetry breaking origin (Hidden sector) MSSM (Visible sector)

  6. Minimal Supergravity • Assume universal scalar and gaugino masses @ GUT scale • Terms in Lsoft determined by just 4 parameters: m1/2 = f<F>/MPl , m02 = (k+n2)|<F>|2/MPl2 , A0 = (α+3n)<F>/MPl , B0 = (β+2n)<F>/MPl , (α,β,f,k,n dimensionless parameters of order 1, determined by full underlying theory) • Eliminate B0 in favor of tanβ, and include sign of μ (value of μ fixed by requiring correct Z mass in Higgs potential)  4 parameters describe the complete theory! m1/2 , m0 , A0 , tanβ, sgn μ known as mSUGRA or Constrained MSSM

  7. Evolution of Scalar/Gaugino Masses • Evolve common scalar/gaugino masses from GUT scale via RGE’s • Gauge couplings increase mass, Yukawa couplings decrease mass • Results in predictive SUSY spectrum @ EW scale w/ Bino as LSP • M3 : M2 : M1 = g32 : g22 : (5/3)gY2 |GUT yields M3 : M2 : M1 = 7 : 2 : 1 |EW

  8. Gauge-Mediated SUSY Breaking messengers • vev <F> in hidden sector breaks SUSY • Communicated to visible sector by SM gauge interactions • msoft arise from loop diagrams containing messenger particles (new chiral supermultiplets) • msoft ~ αa<F>/4πMmessenger • msoft ~ 100 GeV if √<F> ~ Mmess ~ 104 GeV Supersymmetry breaking origin (Hidden sector) MSSM (Visible sector)

  9. Minimal Gauge Mediation • Messenger supermultiplets split by SUSY breaking in • hidden sector • Communicated to MSSM through radiative corrections • Gaugino masses arise from 1-loop diagrams involving messenger particles • Scalar masses arise from 2-loop diagrams

  10. Minimal Gauge Mediation • Masses depend on • Messenger scale • Number of SU(5) 5+5-bar messenger representations • Number and strength of gauge interactions • Gauginos tend to be heavier than scalars (for N5 >1) • If N5 is too large, there is no unification • Gravitino is the LSP  strikingly different phenomenology!

  11. phenomenological MSSM • Most general CP-conserving MSSM • Minimal Flavor Violation • Lightest neutralino is the LSP • First 2 sfermion generations are degenerate w/ negligible Yukawas • No GUT, SUSY-breaking assumptions! • ⇒19(20) real, weak-scale parameters scalars: mQ1, mQ3, mu1, md1, mu3, md3, mL1, mL3, me1, me3 gauginos: M1, M2, M3 tri-linear couplings: Ab, At, Aτ Higgs/Higgsino: μ, MA, tanβ (Gravitino mass, if Gravitino LSP)

  12. SUSY Spectrum • Details of the sparticle spectrum depend on the soft SUSY breaking mechanism! • Precision measurements of the sparticle masses can reveal insight into the soft SUSY breaking mechanism!

  13. Sample Sparticle Spectra: CMSSM and GMSB Gravity mediated Gauge mediated

  14. The SUSY Higgs Sector • SUSY Higgs sector: h0, H0, H±, A0 • 2 free parameters in the Higgs potential: very predictive at tree-level! • Radiative corrections are important! Higgs mass is very senistive in particular to the lightest stop mass

  15. The SUSY Higgs Sector MStop Haber, Hempfling ~ A heavy h0 needs a heavy stop-squark t1

  16. Predictions for Lightest Higgs Mass in the CMSSM • Χ2 fit to EW, Flavor, Collider, Cosmology global data set Ellis etal arXiv:0706.0652

  17. Predictions for Lightest Higgs Mass in the pMSSM Models consistent with EW Precision, B Physics, Cosmology, and Collider data Neutralino LSP Gravitino LSP Cahill-Rowley, JLH, Ismail, Rizzo

  18. 125 GeV Higgs Constraints Maximum mass for h0 in various SUSY breaking scenarios Simplest versions of GMSB, AMSB, etc are ruled out!! 1112.3028

  19. Supersymmetry and Naturalness ~ The hierarchy problem needs a light stop-squark t1

  20. Tension???

  21. Naturalness Criterion • Standard prescription to compute fine-tuning: • Take mass relation w/ radiative corrections • Compute dependence on each SUSY parameter, pi • Overall fine-tuning of model given by • Δ = max|Zi| + higher order Barbieri, Giudice Kasahara, Freese, Gondolo

  22. Naturalness and the CMSSM CMSSM global fit to the data before LHC SUSY search results

  23. Naturalness and the CMSSM CMSSM global fit to the data AFTER LHC SUSY search results

  24. Naturalness and the CMSSM Fine-tuning parameter Δ > 500 – 1000 in the CMSSM The CMSSM is untenable at this time Report submitted to European Strategy

  25. A Natural Spectrum Barbieri

  26. Future Searches • “Naturalness” dictates: • Stop < 700 GeV • Gluino < 1500 GeV • Dedicated searches for direct stop/sbottom and EW gaugino production will be a focus for the rest of the 8 TeV run • Can more complex models accommodate Naturalness?

  27. Study of the pMSSM Linear Priors Perform large scan over Parameters 100 GeV  msfermions  4 TeV 50 GeV  |M1, M2, |  4 TeV 400 GeV  M3  4 TeV 100 GeV  MA  4 TeV 1  tan  60 |At,b,|  4 TeV • Subject these points to • Constraints from: • Flavor physics • EW precision measurements • Collider searches • Cosmology ~225,000 viable models survive constraints! Cahill-Rowley, JLH, Ismail, Rizzo

  28. Subject these Models to LHC Searches Light squarks Gluinos Stop Sparticle distributions: Before LHC 7 TeV 1 fb-1 7 TeV 5 fb-1 8 TeV 5 fb-1 5 TeV 20 fb-1

  29. Non-MET Searches • Non-MET searches are also important! Bsμμ

  30. Fine-Tuning in the pMSSM NeutralinoLSP GravitinoLSP mh = 125 ± 2 GeV

  31. Fine-Tuning in the pMSSM NeutralinoLSP GravitinoLSP mh = 125 ± 2 GeV 13 + 1 models with Δ < 100

  32. Sample Spectra w/ low FT

  33. Sample Spectra w/ low FT

  34. Light Stop Decay Channels

  35. Dark Matter Direct Detection

  36. Summary • Weak-scale Supersymmetry extremely well motivated • Simplest models (CMSSM) in tension with LHC searches • Some minimal models excluded by 125 GeV Higgs (GMSB, AMSB) • More complex scenarios (pMSSM) are still robust • Don’t give up on Weak-scale SUSY until 14 TeV with 300 fb-1 !

  37. The theory community is presently working hard in light of the LHC results! A. Pomarol, ICHEP 2012

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