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何红建 清华大学

LHC: Seeking the Origin of Symmetry Breaking and Mass LHC: 探索对称性破缺与质量起源. 何红建 清华大学. Nanchang, April 17-19, 2010. LHC: this not the end of the beginning --. It is beginning of the new start !. L. H. C. LHC Runs: 7 TeV… 10 TeV… 14 TeV……. What discovery expected at LHC ?

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何红建 清华大学

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  1. LHC: Seeking the Origin of Symmetry Breaking and Mass LHC: 探索对称性破缺与质量起源 何红建 清华大学 Nanchang, April 17-19, 2010.

  2. LHC: this not the end of the beginning-- It is beginning of the new start ! L H C

  3. LHC Runs: 7TeV…10TeV…14TeV…… What discovery expected at LHC ? What should Wedo for it ?

  4. All Matter(Spin-1/2)+Forces(Spin-1) are discovered in SM! The only Missing Particle: Higgs Boson H0 (Spin-0). Higgs Boson gives Masses to All Particles except γ, gluons.

  5. All SM Particles: Area of circle ∝ Particle-MassOnly Top, W/Z and Higgs stand out !

  6. All spin-1/2 matter particles have Masses∝Arbitrary Yukawa Couplings: ( Mw = g v/2 ) ??

  7. SM: (Un)Naturalness of Matter Masses • Only Top & Neutrino masses are Natural (adding Right-handed Neutrinos): • But,WhyAll Other Yukawa’sso tiny ?? e.g.,

  8. It is often said that LHC is just to finda light fundamental Higgs Boson. BUT, this is a quite misleading statement － 1. Higgs Boson may be heavy. 2. Higgs may be more than one and charged. 3. Higgs Boson may be composite. 4. Higgs Boson may Not exit at all. 5. Smoking-Gun Signals other than Higgs.

  9. See: Gian Giudice (CERN), talk at Tsinghua on 3-28-2010 The two best measurements of sin2W do notagree : NO compelling evidence for Light Higgs Boson even in SM ! ★Possibility of Heavy Higgs or No Higgs is fully open ! 10

  10. Heavy Higgs vs Precision Data:No Problem ! HJH etal, TopSeesaw Composite Higgs mH ≈ 400-500GeV Top Seesaw Model

  11. “Natural” SUSY requires heavier Higgs too ! MSSM is already Fine-tuned ! ’ Barbieri et al, 1004.2256 ’ Extended SUSYs give:

  12. Fine-Tuning Problem ? ● Radiative Corrections to Higgs Mass: ●Degree of Fine-Tuning (DFT):

  13. Fine-Tuning is aTechnical Problem ! 14.5TeV 10TeV 7TeV 6.5TeV 3TeV 0.01 0.05 Not strong enough for LHC (ILC) !

  14. Mysteries of Mass Origin: What can LHC probe ? ν 10-2 eV GeV • Origin of Electroweak Symmetry Breaking: -- Why are (W, Z) Massive but photon Massless ? • Does t-Quark conspire Electroweak Symmetry Breaking: -- Why is t-Quark Mass so Close to W/Z Masses ? • Why is Neutrino Mass so tiny ? →SeesawMechanism !

  15. Origin of Electroweak Symmetry Breaking:Why Higgs Boson (light or heavy) at all ?!? Real Physics Problem withElectroweak Symmetry Breakingis Unitarity Violation inHigh Energy Scattering!!!!!

  16. Unitarity of WLWL → WLWL: Electroweak Symmetry Breaking Scale No Way to Escape this Physics Bound !!! MuchStronger & More RobustthanFine-tuning bound!

  17. 0.7

  18. A New Way to RestoreUnitarity:Higgsless Theory!!! Crucial Observation: New Spin-1 Gauge Bosons can Replace Spin-0 Higgs to Restore Unitarity !!! Chivukula,Dicus,He, 2001:New Gauge Bosons from 5d-KK Chivukula,He, 2002: New Gauge Bosons from 4d-Deconstruction and 19 series papers in 2003-2009

  19. LHC Signals for Higgsless W1 Boson: • pp→W1Z→WZZ→jj+4Leptons • pp→jjWZ (including WZ─W1*→WZ→3l+nu) HJH, YPK,YHQ, BZ & MSU arXiv:0708.2588

  20. HJH, YPK, YHQ, BZ & MSU LHC Sensitivity for W1in WZZ & jjWZ Channels:

  21. Does top-Quark ConspireElectroweak Symmetry Breaking ?? Whyist-Quark Mass so Close toW/Z Masses ?

  22. 50 Years Ago Lee and Yang, 1956 Parity Ni60

  23. We reveal the Intrinsic Connection between Spontaneous Parity Violation (SPV) and Electroweak Symmetry Breaking (EWSB) • SPV Scaleis tied toTeV Scale • SPV InducesEWSB (W,Z Masses) as Uniquely fixed by Top-quark Mass = 174 GeV

  24. Predictions: A Sample Higgs Spectrum ： E.g.

  25. LHC Discovery: Luminosity vs Higgs Mass

  26. Signals at the LHC:and pp (gb) → t H+→ t t b. pp → WR→ bbW

  27. New Physics that LHC canNot do ? Scales of Fermion Mass Generation

  28. Exciting Future: After LHC !!!

  29. New Physics that LHC cannot do: Neutrino Mixing,CP-Violation, Matter-Antimatter Asymmetry…

  30. Daya Bay’s Physics Potential on θ13is Non-trivial to justify:

  31. Our Theory Prediction givesstrongest support forDaya Bay !!! Ge, He, Yin, JCAP(2010), 1001.0940

  32. Nature may be more complicated and more interesting than we naively thouhght !! Many New Scales ? Many New Forces ? Is Gravity Emergent? Is M_Planck fundamental? 1019 GeV KeV TeV

  33. 2010 ─ 2030 Keep Your MindFully Open !!!

  34. Thank You !

  35. Backup Slides

  36. 4 Fundamental Forces evolve back withTime/Temperature(Energy):Unification?

  37. New Physics at TeV Scale ? • Hierarchy/Fine-Tuning Problem ? →Not strong enough ! • Unification ? →Many possible realizations ! • Light Higgs ? →Not enforced by data ! • Then, WHAT best justifies TeV Scale?…

  38. Fine-Tuning Problem ? SM Higgs Mass 1-Loop Quadratical Divergence: Quadratical Divergence vanishes if →No Fine-Tuning for MH around 300GeV !

  39. SM Higgs Potential runs intomore seriousVacuum Energy Problemeven at TREE-Level: (eg, S.Weinberg, 1989) <ρ> = Vmin–λv4/4 = Vmin－O(100GeV)4 == (2∙10-3eV)4 → 55 Ordersof Magnitude Fine-tuning ! Soft Breaking SUSY faces the same problem! So, WHY do we care 1% Tuning at 1-Loop?! Neutrino Mass !

  40. RSC, DAD, HJH

  41. VLHC: http://vlhc.org(50-200TeV)

  42. Lessons: (1) A Good Theory ! (2) Vigorous Experiments !! (3) Courage !!!

  43. Conclusions: Origin of Masses, TeV Scale & LHC • Why TeV Scale: ( Strongest Bound is from Unitarity ! ) Unitarity of WLWL → WLWL ( < 1.2TeV ) Justify 1TeV Scale for LHC + ILC !! • What New Physics: Higss vs HiggsLess + SPV Light Higgs or Heavy Higgs or HiggsLess; 4d Deconstruction vs Extra-dim →Unitarity ! New Spin-1 Gauge Bosons Restore Unitarity !! • How to Observe New Gauge Bosons:Signalsvs Bkgnds LHC is very Promising to find W1by 2011-12 !!!

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