Summary and Conclusions

1. Summary and Conclusions John Ellis King’s College London & CERN

2. Open Questions beyond the Standard Model • What is the origin of particle masses? due to a Higgs boson? • Why so many types of matter particles? • What is the dark matter in the Universe? • Unification of fundamental forces? • Quantum theory of gravity? LHC LHC LHC LHC LHC

3. The basis for everything at the LHC Producing new particles • e.g., Higgs Possible signals • e.g., boosted jets Backgrounds • e.g., jets, pile-up Cosmic rays • forward production

4. Soft QCD • Underlying event (Mt, MW): • Pile-up, colour reconnection, … • Important for some BSM signatures: • RPV, long-lived, … • Interesting in own right: • Totalσ, single, multiple rapidity gaps, • Exclusive Higgs production: 420m, CPV? • Near-side ridge: cf, heavy ions? • Forward particles: cosmic rays

5. QCD Theory • Lund string vs clusters: “no new ideas in 30 years” • Continuing work towards universal MC tunes • Which experimental measurements would help make better event generators? • From soft to hard: • Showers with Catani-Seymour dipoles • Matrix element-parton shower matching: • differences for Higgs pT • Boosted jets

6. Hard QCD • Many perturbativeQCD calculations to NNLO • Precision important for discovery & interpretation • New input from string methodology • ✓ over many orders, to pT > 2 TeV • Measurement of αs • Unsung PDF heroes • BUT: convergence for ggH? • Better scheme than MSbar? • ISR? e.g., for dark matter search

7. Hot and Dense Nuclear Matter • Explore QCD thermodynamics: • QGP, CSB, deconfinement, … • Signatures: • Particle abundances: few protons? • Strangeness enhancement • Direct photon production: TLHC = 1.37 TRHIC • J/Ψ, ϒ suppression, recombination • Elliptic flowv2, etc.: small η • Jet quenching

8. Quark-Hadron Phase Diagram • As energy density increases: • Nuclear liquid (A) meson gas (B)  “perfect” liquid (C)  gas asymptotically at higher T? (D) D C B B D A C

9. Multiverse of Little Bangs • Thermalizationat speed of light • Initial conditions, fluid properties • Various vn:hydrodynamics • AdS/CFT “bound”: η ≥ 1/4π • RHIC: η < (3 to 6)/4π • LHC: η< (2 to 3)/4π • Jet quenching • Dijet energy asymmetry • Near-side ridge(s): collective effects in pp, p-Pb?

10. Electroweak Measurements • Impressive progress at LHC • Mt comparable to TeVatron • BUT: challenges for MW: • pile-up, low-x PDFs, material, … • First measurement of sin2θW = 0.2297 ± 0.0010 • Single boson production cross section large?

11. Electroweak Measurements • Diboson production  constraints on couplings • BUT: need more accurate dibosonσcalculation • Limited sensitivity to tribosons • Parameterize vertices using Leff • Run at low pile-up?

12. Electroweak Theory • From LEP paradox to LHC paradox • Light Higgs + nothing else? • If something light, why no indirect evidence? • If nothing light, is light Higgs unnatural? • Electroweak and Higgs coupling measurements complement searchesfor New Physics

13. Top Physics • Interesting, independently of electroweak theory • Added interest in view of EW • Does top have partner: stop? T5/3, … • Why are t and H living dangerously? • Coincidence that (Mh, Mt) close to stability boundary?

14. Top Measurements • Many production mechanisms @ LHC: • ttbar, single t, t + W/H, 4t? • What do we know so far? • Vtb ~ 1 • δMt ~ 0.5%, LHC to improve (but colour reconnection, etc.) • Spin measurements • Puzzle of AFB: • Measure Al • Ac@ LHC

15. Flavour Physics • CKM picture works very well • Dominates over new physics • 2 + 13 modes of CPV • In K0, B0, B±, Bssystems • D0? New LHCbresults  • Also rare decays: Bsμ+μ- • Any new physics at TeV scale must copy CKM • Minimal flavour violation

16. Prospects @ LHC • Not just LHCb, also CMS & ATLAS • Bsμ+μ-: important constraint on BSM • Need to push down to SM error • Measure Bdμ+μ- • Is Bsτ+τ- observable? • B K*μ+μ-: AFB zero crossing point ~ SM • LHCb upgrade in 2018: • 40 MHz, trigger in software • L = 2 × 1033, 50/fb • Aim at φs, D CPV @ SM level, …

17. B Factories • Measurements of sin 2β with error ~ LHCb/3 • World leaders for α = 89.5+6.0-6.3, γ = 67 ± 11 • B Xγand Bτν constrain NP • Some puzzles: • B D*τν 3σ from SM • SuperKEKB: luminosity × 40 • Complementarity to LHCb • Some unique capabilities: • Decays to νν; cand τ decays

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

19. But the Higgs Boson Guralnik, Hagen & Kibble Englert & Brout Higgs Also Goldstone in global case

20. A Phenomenological Profile of the Higgs Boson • First attempt at systematic survey

21. Higgsdependence Day!

22. From Discovery to Measurement • Mass measurements: 125.6 ± 0.3 GeV • Signal strengths ~ SM in many channels • Frontiers: • VBF significance 2σ in several channels, 3σ combined • Decay to ττ emerging, limits on ττ (μτ, eτ) • Decay to bbbar emerging (CMS, Tevatron) • Indirect evidence for ttbar coupling (search for ttbar + H/W, Zγ)

23. Couples like Higgs of Standard Model • No indication of any significant deviation from the Standard Model predictions JE & Tevong You, arXiv:1303.3879

24. The Particle Higgsaw Puzzle Is LHC finding the missing piece? Is it the right shape? Is it the right size?

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

26. What is it ? • Does it have spin 0 or 2? • Is it scalar or pseudoscalar? • Is it elementary or composite? • Does it couple to particle masses? • Quantum (loop) corrections? • What are its self-couplings?

27. Does the ‘Higgs’ have Spin Two ? • Discriminate spin 2 vs spin 0 via angular distribution of decays into γγ JE & Hwang: arXiv:1202.6660 Monte Carlo simulations 2+ disfavoured @ 99% JE, Fok, Hwang, Sanz & You: arXiv:1210.5229

28. The ‘Higgs’ is probably a scalar • Pseudoscalar 0-disfavoured at > 99% CL

29. 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

30. 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

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

32. What is it ? Beyond any Reasonable Doubt • Does it have spin 0 or 2? • Simple spin 2 couplings excluded • Is it scalar or pseudoscalar? • Pseudoscalar strongly disfavoured • Is it elementary or composite? • No significant deviations from Standard Model • Does it couple to particle masses? • Prima facie evidence that it does • Quantum (loop) corrections? • γγ coupling > Standard Model? • What are its self-couplings? Hi-lumi LHC or …?

33. A or The? • Others? • Upper limits on couplings of massive H’ • Extra singlet? 2HDM? Fermiophobic? MSSM? • Non-SM decays? • Invisible decays? SM4? μμ? ττ? aa? H±±? • VV scattering? • Closure test • Another way? Other scenarios? • Precision of BSM predictions? • Will the HL-LHC be enough?

34. Completing the Holy Trinity • Hierarchy possible only in theory that can be calculated over many magnitudes of energy “Renormalizable” • Theorem: (1) vectors (2) fermions (3) scalars • Need to specify: (1) group (2) representations (3) symmetry breaking (1) = SU(3) × SU(2) × U(1) [so far] (2) = Singlets + doublets + triplets • Finally: (3) A scalar and the mechanism of symmetry breaking Cornwall, Levin & Tiktopoulos; Bell;Llewellyn-Smith

35. 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 Degrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:1205.6497

36. Theoretical Confusion • High mortality rate among theories • (MH, Mt) close to stability bound • Λ close to Weinberg upper bound • Split SUSY? High-scale SUSY? • Modify/abandon naturalness? Does Nature care? • String landscape? • SUSY anywhere better than nowhere • SUSY could not explain the hierarchy • New ideas needed!

37. The Dog(s) that did not Bark • To Sherlock Holmes: “Is there any other point to which you would wish to draw my attention?” • Holmes: "To the curious incident of the dog in the night-time." • To Holmes: "The dog did nothing in the night-time." • Holmes: "That was the curious incident.” • We have many clues: Waiting for our Holmes: maybe a string player?

38. Neutrino Models • No convincing models • Anarchy works just fine! • Normal or inverted hierarchy? • Majorana or Dirac masses? (*) • CP violation? (*) • (*) Important in principle for leptogenesis, but not sufficient to calculate it • Main competition weak-scale baryogenesis? • Seesaw mass scale accessible at LHC?

39. Neutrino Experiments • Hierachy of masses? • ‘Holy Grail’ of CP violation? • ESS 400 MeV ν source, Water Č • Sterile neutrinos? • LSND, MiniBooNE, reactor anomaly • Possible experiments: • IsoDAR, ICARUS/NESSIE (CERN) • Towards another ‘Holy Grail’? • Cosmic neutrino background using Mcu of Tritium

40. Astroparticle Physics • Focus on dark matter  LHC • Interesting other topics: • VHE ν’s in IceCube • Inflation (Planck): Higgs boson? • Dark matter: axions or WIMPs? • Strong CP problem not same naturalness problem as Mh • ADMX experiment probing dark matter parameter space

41. Cosmological Inflation in Light of Planck • A scalar in the sky?

42. Inflationary Models in Light of Planck • Planck CMB observations consistent with inflation • Tilted scalar perturbation spectrum: ns = 0.9603 ± 0.073 • BUT strengthened upper limit on tensor perturbations: r < 0.10 • Challenge for simple inflationary models • Starobinsky R2 to rescue? • Similar predictions from Higgs inflation

43. If at first you don’t succeed … • … postulate a new particle: • QM and Special Relativity: Antimatter • Nuclear spectra: Neutron • Continuous spectrum in β decay: Neutrino • Nucleon-nucleon interactions: Pion • Absence of lepton number violation: Second neutrino • Flavour SU(3): Ω- • Flavour SU(3): Quarks • FCNC: Charm • CP violation: Third generation • Strong dynamics: Gluons • Weak interactions: W±, Z0 • Renormalizability: H • Dark matter: WIMP/axion?

44. WIMP Searches • Direct search for dark matter scattering: • Spin-independent and –dependent σlimits from XENON100, COUPP • CoGeNT & DAMA well excluded • 3 CDMS candidates (~threshold, compatibility with XENON100?) • Cf, monojet searches at LHC: • LHC wins for interactions with quarks and gluons • XENON, DARWIN, EURECA

45. Indirect WIMP Searches • Rising positron fraction? • Require large boost factor • Limits from γrays • No antiproton signal • Fermi γline @ 130 GeV: 4.6 σ (3.3 σ with look-elswhere effect) • Need σ > SUSY? • Seen from earth’s limb! • Test with HESS-II et al. Falsify WIMP hypothesis?

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

47. Data • Electroweak precision observables • Flavour physics observables • gμ - 2 • Higgs mass • Dark matter • LHC Deviation from Standard Model: Supersymmetry at low scale, or …? MasterCode: O.Buchmueller, JE et al.

48. 1 5 Gluino mass CMSSM Yesterday’s update of Buchmueller, JE et al: arXiv:1207.3715 Favoured values of gluino mass significantly above pre-LHC, > 1.5 TeV

49. Towardsuniversal mass limits in SUSY • Many searches in specific scenarios: • CMSSM, “natural”, (over)simplified models • Combination may be less model-dependent Buchmueller & Marrouche

50. 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, … • A photon-photon collider: SAPPHiRE • A muon collider