From an obscure term in an equation to a headline discovery – and beyond

1. Different Scales for Higgs Physics From an obscure term in an equation to a headline discovery – and beyond John Ellis King’s College London (& CERN)

2. The (G)AEBHGHKMP’tH Mechanism The only one who mentioned a massive scalar boson

3. Why a Higgs Boson is Needed • Trouble with WW scattering: M ~ E2  uncontrollable infinities in loop diagrams • can be cancelled by • scalar exchange with HWW couplings • Need new physics @ TeV scale

4. 2011: Combining Information from Previous Direct Searches and Indirect Data mH = 125 ± 10 GeV Gfitter collaboration

5. Higgs Mass Measurements • CMS γγ and ZZ* measurements consistent

6. Higgs Mass Measurements • Tension in ATLAS γγ and ZZ* measurements

7. Comparison with Electroweak Fit Quite consistent: Δχ2 ~ 1.5

8. Theoretical Constraints on Higgs Mass • Large Mh → large self-coupling → blow up at low-energy scale Λ due to renormalization • Small: renormalization due to t quark drives quartic coupling < 0 at some scale Λ → vacuum unstable • Vacuum could be stabilized by Supersymmetry Instability @ 1010 – 1013 GeV Degrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:1205.6497

9. Vacuum Instability in the Standard Model • Very sensitive to mt as well as MH • Present vacuum probably metastable with lifetime >> age of the Universe Degrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:1205.6497

10. Some Questions • What is it? • Higgs or …? • What else is there? • Supersymmetry …? • What next? • A Higgs factory or …? Supersymmetric model fits

11. Higgs field: <0|H|0> ≠ 0 Quantum loop problems Fermion-antifermion condensate Just like QCD, BCS superconductivity Top-antitop condensate? needed mt > 200 GeV Elementary Higgs or Composite? e.g., cutoff Λ = 10 TeV New technicolour force? • Heavy scalar resonance? • Inconsistent with precision electroweak data? Cut-off Λ ~ 1 TeV with Supersymmetry?

12. Higgs as a Pseudo-Goldstone Boson ‘Little Higgs’ models (breakdown of larger symmetry) Loop cancellation mechanism Little Higgs Supersymmetry

13. Phenomenological Framework • Assume custodial symmetry: • Parameterize gauge bosons by 2 × 2 matrix Σ: • Coefficients a = c = 1 in Standard Model

14. Global Analysis of Higgs-like Models • Rescale couplings: to bosons by a, to fermions by c • Standard Model: a = c = 1 No evidence for deviation from SM W W Global b bbar τ τ γ γ Z Z JE & Tevong You, arXiv:1303.3879

15. It Walks and Quacks like a Higgs • Do couplings scale ~ mass? With scale = v? • Red line = SM, dashed line = best fit Global fit JE & Tevong You, arXiv:1303.3879

16. Loop Corrections ? • ATLAS sees excess in γγ, CMS sees deficit • Loop diagrams ~ Standard Model? JE & Tevong You, arXiv:1303.3879

17. What else is there? • Higher-dimensional operators as relics of higher-energy physics? • Operators constrained by SU(2) × U(1) symmetry: • Constrain using LHC + Tevatron Higgs measurements Corbett, Eboli & Gonzalez2

18. What else is there? Combine Higgs coupling measurements with constraints on anomalous triple-gauge boson couplings Corbett, Eboli & Gonzalez2

19. What else is there? Constraints from energy dependence of Higgs production cross section on Λ > ~ 250 GeV JE, Sanz & You, arXiv:1303.0208

20. What else is there? Supersymmetry • Successful prediction for Higgs mass • Should be < 130 GeV in simple models • Successful predictions for Higgs couplings • Should be within few % of SM values • Could explain the dark matter • Naturalness, GUTs, string, … (???)

21. MSSM Higgs Masses & Couplings Lightest Higgs mass up to ~ 130 GeV Heavy Higgs masses quite close Consistent With LHC

22. Searches ~ 5/fb @ 8 TeV Searches with 8 TeV Data “Classic” missing-energy search Multiple searches including b, leptons

23. 2 5 Scan of CMSSM Impacts of searches with full 2012 data Update of Buchmueller et al: arXiv:1207.3715 p-value of simple models < 10%

24. 1 5 Gluino mass CMSSM Update of Buchmueller, JE et al: arXiv:1207.3715 Favoured values of gluino mass significantly above pre-LHC, > 1.5 TeV

25. 2 5 Spin-independent Dark matter scattering --- 1/fb ___ 5/fb Excluded by XENON100 Excluded by LHC Buchmueller, JE et al: arXiv:1207.3715 Favoured values of dark matter scattering cross section significantly below XENON100

26. What Next: A Higgs Factory? To study the ‘Higgs’ in detail: • The LHC • Rethink LHC upgrades in this perspective? • A linear collider? • ILC up to 500 GeV • CLIC up to 3 TeV (Larger cross section at higher energies) • A circular e+e- collider: LEP3, TLEP • A photon-photon collider: SAPPHiRE • A muon collider

27. What Higgs Factory? New large tunnel could also be used for pp collisions ECM up to 100 TeV TLEP Steering Group, arXiv:1208.0504, 1305.6498, 1306.5981

28. Possible Layouts for TLEP

29. Comparison of Possible HiggsFactory Measurements

30. Impact of Higgs Factory? • Predictions of current best fits in simple SUSY models • Current uncertainties in SM calculations [LHC Higgs WG] • Comparisons with • LHC • HL-LHC • ILC • TLEP • Don’t decide before LHC 13/4 Supersymmetric model fits

31. Part of a Vision for the Future • A large circular tunnel • Circumference ~ 80 to 100 km • Could accommodate TLEP and VHE-LHC • ECM up to 100 TeV with 15 Tesla magnets • Could be sited around Geneva • Interest in China, US • TLEP Study Group under way • Timely to study VHE-LHC

32. Conversation with Mrs Thatcher: 1982 Wouldn’t it be better if they found what you predicted? Think of things for the experiments to look for, and hope they find something different What do you do? Then we would not know how to progress!