1. Hong-Jian He Tsinghua University Physics Case for Circular Colliders Physics Case for Circular Colliders International WS on FHECC, IHEP, Beijing, Dec.16-17, 2013.

2. High Energy Physics at Turning Point  LHC Discovery of H(125GeV) in 2012 is a Historic Turning Point － SM seems complete. Historic Turning Point － SM seems complete.  Leads to a New Set of Key Physics Questions !  High Energy Frontier: Needs Global Effort & Global Program, world-wide! Needs Global Effort & Global Program, world-wide!  Circular Colliders: a Major Direction of Future High Energy Colliders. a Major Direction of Future High Energy Colliders. LEP-LHC is such an example with Great Success! LEP-LHC is such an example with Great Success! — So, What’s the Next ?! — So, What’s the Next ?!

3. Physics Discoveries on Energy Frontier vs Advances in Accelerator/Technology VLHC ILC Snowmass-2013

4. TLEP+VHE-LHC ee(350GeV)+pp(100TeV) TLEP Proposal (arXiv:1308.6176)

5. Circular Higgs factory (Phase I) + Super pp Collider (Phase II) in the Same Tunnel e  e + Higgs Factory Super pp collider Circular ee Collider (CEPC) + Super pp Collider (SPPC) A Chinese Proposal

6. High Energy Physics at Turning Point High Energy Physics at Turning Point New Set of Key Physics Questions LHC New Discovery of H(125GeV) puts leading to

7. New Set of Key Physics Questions Within SM Structure New Set of Key Physics Questions Within SM Structure SM contains 3 kinds of Fundamental Interactions: SM contains 3 kinds of Fundamental Interactions:  1. Gauge Interactions: via Spin-1 Gauge Bosons  2. Yukawa Interactions: via Spin-0 Higgs Boson  3. Higgs Self-Interactions: via h 3 and h 4 Couplings  LHC only has weak sensitivities to hττ, hbb, htt. ─ All other Yukawa + Self couplings fully unknown!! ─ All other Yukawa + Self couplings fully unknown!! ─ Origins of Fermion Masses + Higgs Mass Itself ?? ─ Origins of Fermion Masses + Higgs Mass Itself ??  Quantitative Tests of Type-1(h) + Type-2,3 Interactions are KEY Tasks for Next Generation Colliders !!! are KEY Tasks for Next Generation Colliders !!!

8. Sensitivity to Higgs Couplings: M.E.Peskin, arXiv:1207.2516 LHC(300/fb) has poor sensitivity to Fermion-Yukawa-Couplings !

9. Sensitivity to Higgs Couplings: M.Klute etal, arXiv:1301.1322 HL-LHC(3/ab) does not improve much on Yukawa Couplings !

10. Theory Predictions for Modifications

11. New Set of Key Physics Questions Beyond SM Structure New Set of Key Physics Questions Beyond SM Structure  SM does not include Gravity Force ! So it cannot explain Dark Energy, Inflation..... So it cannot explain Dark Energy, Inflation.....  85% Matter in the universe is Dark Matter, but SM contains no DM ! but SM contains no DM !  SM with h(125GeV) gives too small Baryon Asymmetry of the universe, in contradiction with observations !  SM cannot account for Neutrino Mass without adding New Particles. New Particles.  ν Mixings fully differ from Quarks. Leptonic CP ?…

12. High Energy Physics at Turning Point Additional Remarks High Energy Physics at Turning Point Additional Remarks  H(125) completes SM spectrum. We enter a New Era where Verification of SM takes 2nd Place to Search for New Forces & Interactions. Search for New Forces & Interactions.  A Mystery concerns Higgs Itself: It gives masses to all SM particles － Why is God Particle as simple as this? Why is Higgs mass sensitive to Heavy Particles in UV ? Why is Higgs mass sensitive to Heavy Particles in UV ?  Higgs itself gives us a New Exp approach: Once SM Higgs is extended, its properties are hardly constrained. It is compelling to tug on this particle until SM breaks !!

13. What LHC-14 at 300/fb Will Do ?  Increase mass reach by a factor ~2 in most channels. Search glunio to ~2TeV, Z’, t’ above 1TeV, …… Search glunio to ~2TeV, Z’, t’ above 1TeV, ……  Make 1st measurement on V V V V Scattering.  Test h gauge couplings, mass, spin, CP to 10% level.  Give 1st measurement on h-t-t coupling.  Measure M W to precision < 10MeV, M t to < 600MeV.  Measure t couplings to Z, W, g, γ with sensitivities increased by a factor 2-5 better than today.  Carry out ISR-based searches for DM particles.  Provide data for new generation of PDFs. ………

14. What HL-LHC at 3/ab Will Do ? What HL-LHC at 3/ab Will Do ?  Increase mass reach by 20-40% for generic New Particle searches; increase a factor-2 in mass reach via EW force searches; increase a factor-2 in mass reach via EW force  Make precise measurement on V V V V Scattering, to probe Higgs sector resonance. to probe Higgs sector resonance.  Test Higgs couplings to 2-10%, 1% for h γγ /hZZ ratio.  Make powerful searches for Extended Higgs Sector.  Measure Rare Decays h μμ,γZ with 100M Higgs bosons.  Measure M W to precision < 5MeV, M t to < 500MeV.  Search for flavor-changing t couplings with 10B t-quarks.  Follow up an earlier discovery at LHC or in DM searches …

15. Circular e + e - Higgs Factory at 240GeV  Offer 10 times higher Luminosity than ILC(240), improve Higgs Coupling measurements by factor 3, and provide Multiple Detectors working at the same time.  Make better measurements than ILC by factor-4 in sin 2 θ eff, a factor-4 in M W, and a factor-10 in M Z. a factor-4 in M W, and a factor-10 in M Z.  Search for rare top coupling via ee t c, t u.  Offer possible improvement of α s by a factor-5 over Giga-Z, to < 0.1% precision.  TLEP350 measures top mass more precisely to ±100MeV.  …………

16. Circular e + e - : Precision Higgs Machine  e + e - Higgs Factory (240GeV) can more precisely measure Higgs properties than LHC: Mass, J PC, Couplings, especially h-Z-Z, h-b-b, h-τ-τ, h-g-g couplings, and invisible decays. It can also measure h-c-c Coupling, which cannot be carried out at LHC.  Most of important Precision-Higgs-Tests can be already done at HF(240GeV), without ILC500. Higgs self-couplings’ll be probed at Super pp(50-100TeV). M. E. Peskin, arXiv:1207.2516 ILC1(250GeV) & HF(240-250) can do well !

17. Circular HF(240) vs ILC(250) Snowmass-Higgs-Rept, arXiv:1310.8361

18. Circular pp Collider at 50-100TeV  Give high rates for gg hh production, and measure h 3 coupling to 8% at pp(100TeV) with 3/ab luminosity. h 3 coupling to 8% at pp(100TeV) with 3/ab luminosity.  Sensitively search New Higgs bosons of extended Higgs sector in multi-TeV range.  Significantly improve sensitivity to WW Scattering and multi-weak-boson production. multi-weak-boson production.  Search for WIMP DM Particle up to TeV mass range.  Follow up any discovery at LHC or DM & flavor searches, with further probes for related higher-mass particles. with further probes for related higher-mass particles. Both energy + luminosity matter! Both energy + luminosity matter!  ………… Brock & Peskin, Snowmass-Summary-Rept

19. Sensitivity to Higgs Couplings: M.E.Peskin, arXiv:1207.2516v3

20. Collider Reach for New Physics Upper Limits on New Particles Reaches at 95%CL Snowmass-Summary-2013

21. Higgs Gauge Couplings via WW Scattering LHC(14TeV) vs pp(50-100TeV)

23. Higgs Gauge Couplings via WW Scattering LHC(14TeV, 300/fb) Sensitivity: |Δκ| < 0.2 (2σ level)

24. For pp(50-100), we have E_cm(WW) = 10-30TeV. — Sensitive to Δκ ~ O(10 -3 ) J. Ren & HJH

25. For pp(50-100), we have E_cm(WW) = 10-30TeV. — Sensitive to Δκ ~ O(10 -3 ) J. Ren & HJH

26. Modify Effective hWW/hZZ Couplings in Einstein Frame:

27. General Unitarity Bound W + W + W + W + for LHC Energy

28. W + W + W + W + for pp(50-100TeV): — Sensitive to Δκ ~ O(10 -3 ) J. Ren & HJH

29. Origins of Fermion Masses: Probing Yukawa ! All spin-1/2 matter particles have ∝ Masses ∝ Arbitrary Yukawa Couplings: (in SM)

32. Why 2 n Scattering ? Dicus & HJH, 2005

35. PP(50-100TeV): Direct Probe of b & c Yukawa Couplings J. Ren & HJH

36. Testing Higgs Self-Couplings LHC(14TeV) vs pp(50-100TeV) pp hh + X bbγγ h 3 coupling with 50% accuracy.  LHC(14TeV, 3/ab) probe h 3 coupling with 50% accuracy. h 3 coupling with 20% accuracy.  HE-LHC(33TeV, 3/ab) probe h 3 coupling with 20% accuracy. h 3 coupling with 8% accuracy.  pp(100TeV, 3/ab) probe h 3 coupling with 8% accuracy. W. Yao, Snowmass-2013 (arXiv:1308.6302)

37. Can Circular e  e + (240) Probe h 3 Coupling?  TLEP(240GeV) can measure σ[Zh] to 0.4%. Estimate: Can probe h 3 to 28%. Estimate: Can probe h 3 to 28%.  Recall: HL-LHC probes h 3 to 50%. HL-LHC probes h 3 to 50%. ILC500 probes h 3 to 83%. ILC500 probes h 3 to 83%. M. Mcullough, arXiv:1312.3322

38. Beyond Higgs Boson(125) ??? We need: Big Machines + Big Ideas ! Cooperate Exp & Theory !

39. Thanks to Nima as our Great Theory Inspirator !

40. Thanks to All of You for Global Efforts in the World !