Physics Beyond the Standard Model

1. Physics Beyond the Standard Model J. Hewett, ITEP Winter School 2010

2. Why New Physics @ the Terascale? • Electroweak Symmetry breaks at energies ~ 1 TeV (SM Higgs or ???) • WW Scattering unitarized at energies ~ 1 TeV (SM Higgs or ???) • Gauge Hierarchy: Nature is fine-tuned or Higgs mass must be stabilized by New Physics ~ 1 TeV • Dark Matter: Weakly Interacting Massive Particle must have mass ~ 1 TeV to reproduce observed DM density All things point to the Terascale!

3. A Revolution is Upon Us!

4. Science Timeline: The Tools Auger PLANCK LSST/JDEM WMAP Fermi LHC Upgrade Tevatron LHC 2020 2005 2007 2010 2012 2015 2018 LHCb ILC B-Factories T2K/Noa Numi/Minos Super-K Kamland 0 Underground & IndirectDark Matter Searches

5. Science Timeline: The Tools Auger PLANCK LSST/JDEM WMAP Fermi LHC Upgrade Tevatron LHC 2020 2005 2007 2010 2012 2015 2018 LHCb ILC B-Factories T2K/Noa Numi/Minos Super-K Kamland 0 Underground & IndirectDark Matter Searches

6. The Standard Model Brief review of features which guide & restrict BSM physics

7. TheStandardModelofParticlePhysics Building Blocks of Matter: Symmetry: SU(3)C x SU(2)L x U(1)Y QCD Electroweak Spontaneously Broken to QED This structure is experimentally confirmed!

8. The Standard Model on One Page SGauge =  d4x FY FY + F F + Fa Fa SFermions =  d4x   fDf SHiggs =  d4x (DH)†(DH) – m2|H|2 + |H|4 SYukawa =  d4x YuQucH + YdQdcH† + YeLecH† ( SGravity =  d4x g [MPl2 R + CC4] ) Generations f = Q,u,d, L,e

9. Gauged Symmetries Color Electroweak SU(3)C x SU(2)L x U(1)Y Q 3 2 +1/6 uc 3 1 -2/3 dc3 1 +1/3 L 1 2 -1/2 ec1 1 +1 Matter Fermions

10. EW measurements agree with SM predictions @ 2+ loop level Jet production rates @ Tevatron agree with QCD Standard Model predictions well described by data! Pull

11. Search for the Higgs Boson: Tevatron Search Direct Searches at LEP: mH > 114.4 GeV Indirect Searches at LEP/SLC: mH < 186 GeV @ 95% CL Higgs Z Z Z

12. Global Flavor Symmetries Q1 u1 d1 L1 e1 . . 2 . . 3 Rotate 45 fermions into each other U(45) SM matter secretly has a large symmetry: Explicitly broken by gauging 3x2x1 Rotate among generations U(3)Q x U(3)u x U(3)d x U(3)L x U(3)e Explicitly broken by quark Yukawas + CKM Explicitly broken by charged lepton Yukawas U(1)e x U(1) x U(1) Explicitly broken by neutrino masses U(1)B Baryon Number Lepton Number U(1)L (Dirac) (or nothing) (Majorana)

13. Global Symmetries of Higgs Sector 1 + i2 3 + i4 Four real degrees of freedom Higgs Doublet: Secretly transforms as a 1 2 3 4 4 of SO(4) Decomposes into subgroups (2,2) SU(2) x SU(2) SU(2)L of EW Left-over Global Symmetry

14. Global Symmetries of Higgs Sector 1 + i2 3 + i4 Four real degrees of freedom Higgs Doublet: Secretly transforms as a Gauging U(1)Y explicitly breaks Size of this breaking given by Hypercharge coupling g’ 1 2 3 4 SU(2)Global Nothing 4 of SO(4) Decomposes into subgroups MW2 g2 =  1 as g’0 MZ2 g2 + (g’)2 (2,2) SU(2) x SU(2) New Physics may excessively break SU(2)Global SU(2)L of EW Remaining Global Symmetry Custodial Symmetry

15. Standard Model Fermions are Chiral - Fermions cannot simply ‘pair up’ to form mass terms i.e., mfLfR is forbidden

16. Standard Model Fermions are Chiral - Fermions cannot simply ‘pair up’ to form mass terms i.e., mfLfR is forbidden Try it! (Quc) 1 2 -1/2 (Qdc) 1 2 +1/2 (QL) 3 1 -1/3 (Qe) 3 2 +7/6 (ucdc) 3x3 1 -1/3 (ucL) 3 2 -7/6 (uce) 3 1 +1/3 (dcL) 3 2 -5/6 (dce) 3 1 +4/3 (Le) 1 2 +1/2 SU(3)C SU(2)L U(1)Y Fermion masses must be generated by Dimension-4 (Higgs) or higher operators to respect SM gauge invariance! - - - - - -

17. An anomaly leads to a mass for a gauge boson Anomaly Cancellation Quantum violation of current conservation

18. Anomaly Cancellation SU(3) SU(3) SU(2)L SU(2)L U(1)Y U(1)Y g g 3[ 2‧(1/6) – (2/3) + (1/3)] = 0 Q uc dc U(1)Y U(1)Y U(1)Y U(1)Y 3[3‧(1/6) – (1/2)] = 0 Q L 3[ 6‧(1/6)3 + 3‧(-2/3)3 + 3‧(1/3)3 + 2‧(-1/2)3 + 13] = 0 3[(1/6) – (2/3) + (1/3) – (1/2) +1] = 0 Q uc dc L e Can’t add any new fermion  must be chiral or vector-like!

19. Standard Model Summary SU(3)C x SU(2)L x U(1)Y Exact Broken to U(1)QED • Gauge Symmetry • Flavor Symmetry • Custodial Symmetry • Chiral Fermions • Gauge Anomalies U(3)5 U(1)B x U(1)L (?) Explicitly broken by Yukawas SU(2)Custodial of Higgs sector Broken by hypercharge so  = 1 Need Higgs or Higher order operators Restrict quantum numbers of new fermions

20. Standard Model Summary SU(3)C x SU(2)L x U(1)Y Exact Broken to U(1)QED • Gauge Symmetry • Flavor Symmetry • Custodial Symmetry • Chiral Fermions • Gauge Anomalies U(3)5 U(1)B x U(1)L (?) Explicitly broken by Yukawas SU(2)Custodial of Higgs sector Broken by hypercharge so  = 1 Need Higgs or Higher order operators Restrict quantum numbers of new fermions Any model with New Physics must respect these symmetries

21. Standard Model is an Effective field theory An effective field theory has a finite range of applicability in energy: , Cutoff scale Energy Theory is valid Particle masses All interactions consistent with gauged symmetries are permitted, including higher dimensional operators whose mass dimension is compensated for by powers of 

22. Lepton Number Violation Precision Electroweak Generic Operators Flavor Violation CP Violation Baryon Number Violation Contact Operators Constraints on Higher Dimensional Operators

23. 1 Counts charged matter 40 30 Weak scale measurement 2 20 High scale particle content 10 3 (GeV) Gauge coupling unification: Our Telescope

24. Telescope to Unification Unification of Weak and Electromagnetic forces demonstrated at HERA ep collider at DESY  Electroweak theory!

25. 16 Grand Unification Gauge coupling unification indicates forces arise from single entity

26. What sets the cutoff scale  ? • What is the theory above the cutoff? New Physics, Beyond the Standard Model! Three paradigms: • SM parameters are unnatural • New physics introduced to “Naturalize” • SM gauge/matter content complicated • New physics introduced to simplify • Deviation from SM observed in experiment  New physics introduced to explain

27. How unnatural are the SM parameters? Technically Natural • Fermion masses (Yukawa Couplings) • Gauge couplings • CKM Logarithmically sensitive to the cutoff scale • Technically Unnatural • Higgs mass • Cosmological constant • QCD vacuum angle • Power-law sensitivity to the cutoff scale

28. The naturalness problem that has had the greatest impact on collider physics is: The Higgs (mass)2 problem or The hierarchy problem

29. Do we really need a Higgs? Higgs Higgs Bad violation of unitarity A = a s/MW2 + … Restores unitarity A = - a (s – mh2)/MW2 + … Expand cross section into partial waves Unitarity bound (Optical theorem!)  Gives mh < 4MW LHC is designed to explore this entire region!

30. The Hierarchy Energy (GeV) 1019 Planck 1016 GUT desert Future Collider Energies 103 Weak All of known physics Solar System Gravity 10-18

31. The Hierarchy Problem Energy (GeV) 1019 Planck Quantum Corrections: Virtual Effects drag Weak Scale to MPl 1016 GUT desert Future Collider Energies mH2 ~ ~ MPl2 103 Weak All of known physics Solar System Gravity 10-18

32. Electroweak Hierarchy Problem Higgs (mass)2 is quadratically divergent In the SM, mh is naturally ~ Λ, the largest energy scale mh ~ 100 GeV & Λ ~ MPl ~ 1019 GeV → cancellation in one part of 1034

33. A Cellar of New Ideas a classic! aged to perfection better drink now mature, balanced, well developed - the Wino’s choice ’67 The Standard Model ’77 Vin de Technicolor ’70’s Supersymmetry: MSSM ’90’s SUSY Beyond MSSM ’90’s CP Violating Higgs ’98 Extra Dimensions ’02 Little Higgs ’03 Fat Higgs ’03 Higgsless ’04 Split Supersymmetry ’05 Twin Higgs svinters blend all upfront, no finish lacks symmetry bold, peppery, spicy uncertain terrior complex structure young, still tannic needs to develop sleeper of the vintage what a surprise! finely-tuned double the taste J. Hewett

34. Last Minute Model Building Anything Goes! • Non-Communtative Geometries • Return of the 4th Generation • Hidden Valleys • Quirks – Macroscopic Strings • Lee-Wick Field Theories • Unparticle Physics • ….. (We stilll have a bit more time)

35. A Cellar of New Ideas a classic! aged to perfection better drink now mature, balanced, well developed - the Wino’s choice ’67 The Standard Model ’77 Vin de Technicolor ’70’s Supersymmetry: MSSM ’90’s SUSY Beyond MSSM ’90’s CP Violating Higgs ’98 Extra Dimensions ’02 Little Higgs ’03 Fat Higgs ’03 Higgsless ’04 Split Supersymmetry ’05 Twin Higgs svinters blend all upfront, no finish lacks symmetry bold, peppery, spicy uncertain terrior complex structure young, still tannic needs to develop sleeper of the vintage what a surprise! finely-tuned double the taste J. Hewett

36. The Hierarchy Problem: Supersymmetry Energy (GeV) 1019 Planck Quantum Corrections: Virtual Effects drag Weak Scale to MPl 1016 GUT desert boson Future Collider Energies mH2 ~ ~ MPl2 103 Weak fermion ~ - MPl2 mH2 ~ All of known physics Large virtual effects cancel order by order in perturbation theory Solar System Gravity 10-18

37. Supersymmetry Supersymmetry is a new symmetry that relates fermions ↔ bosons

38. Superpartners • Translations: Particle P at point x → Particle P at point x’ • Supersymmetry: Particle P at point x → Particle P at point x • P and P differ by spin ½: fermions ↔ bosons • P and P are identical in all other ways (mass, couplings….) ~ ~ ~ ~ ~ γ γ γ

39. Supersymmetry and Naturalness Dependence on Λ is softened to a logarithm SUSY solves hierarchy problem, if sparticle masses <1 TeV

40. Supersymmetry: Recap • Symmetry between fermions and bosons • Predicts that every particle has a superpartner of • equal mass • Suppresses quantum effects • Can make quantum mechanics consistent with • gravity (with other ingredients)

41. Supersymmetry: Recap • Symmetry between fermions and bosons • Predicts that every particle has a superpartner of • equal mass (  SUSY is broken: many competing models!) • Suppresses quantum effects • Can make quantum mechanics consistent with • gravity (with other ingredients)

42. Higgs Doubling • SUSY requires 2 Higgs doublets to cancel anomalies and to give mass to both up- and down-type particles • Anomaly cancellation requires Σ Y3 = 0, where Y is hypercharge and the sum is over all fermions • SUSY adds an extra fermion with Y = -1 • To cancel this anomaly, we add another Higgs doublet with Y = +1

43. Supersymmetric Parameters

44. Minimal Supersymmetric Standard Model • Conserved multiplicative quantum number (R-parity) • Superpartners are produced in pairs • Heavier Superpartners decay to the Lightest • Lightest Superpartner is stable • Collider signatures dependent on this assumption • and on model of SUSY breaking

45. R-Parity: New Multiplicative Quantum Number • One problem: proton decay! • Forbid this with R-parity conservation: Rp = (-1)3(B-L)+2S • P has Rp = +1; P has Rp = -1 • Requires 2 superpartners in each interaction • Consequence: the Lightest Supersymmetric Particle (LSP) is stable and cosmologically significant. • What is the LSP? ~

46. Neutral SUSY Particles

47. Electroweak Symmetry Breaking

48. Telescope to Unification • Superpartners modify the scale dependence of couplings • With TeV superpartners, the forces are unified! • Unification scale ~ 1016 GeV

49. Telescope to Unification • All parameters have scale dependence • Superpartner mass determinationsprovide tests for unification Evolution of superpartner masses to high scale:

50. SUSY Breaking SUSY is not an exact symmetry We don’t know how SUSY is broken, but SUSY breaking effects can be parameterized in the Lagrangian