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The Higgs Boson & Beyond

The Higgs Boson & Beyond. To Higgs or not to Higgs? just one of the questions being studied at the LHC. John Ellis King ’ s College London (& CERN). Open Questions beyond the Standard Model. What is the origin of particle masses? due to a Higgs boson?

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The Higgs Boson & Beyond

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  1. The Higgs Boson & Beyond To Higgs or not to Higgs? just one of the questions being studied at the LHC 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. Some Questions • What is it? • Higgs or …? • What else is there? • Supersymmetry or …? • What next? • A Higgs factory or …?

  4. The Seminal Papers The only one who mentioned a massive scalar boson

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

  6. A Preview of the Higgs Boson @ LEP • First LEP Yellow Report in 1976: • Higgsstrahlung “Bjorken process”

  7. A Preview of the Higgs Boson @ LHC • Prepared for LHC Lausanne workshop 1984

  8. Estimating the Mass of the Higgs Boson • First attempts in 1990, • Easier after the discovery of the top quark 1991 JE, Fogli & Lisi

  9. Calculating the Mass of the Higgs Boson Expensive – but maybe not my most costly calculation …

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

  11. A la recherche du Higgs perdu … Higgs Production at the LHC Many production modes measurable if Mh ~ 125 GeV

  12. Higgs Decay Branching Ratios • Couplings proportional to masses (?) • Important couplings through loops: • gluon + gluon → Higgs → γγ Many decay modes measurable if Mh ~ 125 GeV

  13. Higgsdependence Day!

  14. Unofficial Combination of Higgs Search Data from December 13th Is this the Higgs Boson? No Higgs here! No Higgs here!

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

  16. 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?

  17. What is the Spin of the ‘Higgs’? • Decays into γγ, so cannot have spin 1 • Spin 0 or 2? • Selections of WW and ZZ events are based on spin 0 hypothesis • Can diagnose spin via • angular distribution of γγ • angular correlations of leptons in WW, ZZ decays • Production in association with W or Z

  18. Does the ‘Higgs’ have Spin Two ? Vector boson + ‘Higgs’ combined invariant mass very different for spins 0 and 2 JE, Hwang. Sanz & You: arXiv:1208.6002

  19. Does the ‘Higgs’ have Spin Two ? • Would have graviton-like couplings: • Coefficients somewhat model-dependent • Warped compactification: • Expect equal couplings for photons, gluons • Larger coefficients for W, Z, b, t • Smaller coefficients for u, d, s, c (Also expect vector mass < tensor mass X LHC) JE, Sanz & You, arXiv:1211.3068

  20. Does the ‘Higgs’ have Spin Two ? • Fit of vector-boson couplings to spin-two model • Prediction of AdS-type graviton-like model disfavoured by > 3 σ JE, Sanz & You, arXiv:1211.3068

  21. 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 JE, Fok, Hwang, Sanz & You: arXiv:1210.5229

  22. The ‘Higgs’ probably does not have Spin Two • ATLAS γγ analysis prefers spin 0 over 2+ • No discrimination from CMS ZZ* analysis 2+ disfavoured @ 91%

  23. What is it ? • Does it have spin 0 or 2? • Spin 2 seems unlikely, but needs experimental checks • Is it scalar or pseudoscalar? • Is it elementary or composite? • Does it couple to particle masses? • Quantum (loop) corrections? • What are its self-couplings?

  24. The ‘Higgs’ probably has Parity + • Kinematic distribution of ZZ* final state • 0- disfavoured @ 97% level

  25. What is it ? • Does it have spin 0 or 2? • Spin 2 seems unlikely, but needs experimental checks • Is it scalar or pseudoscalar? • Pseudoscalardisfavoured by experiment • Is it elementary or composite? • Does it couple to particle masses? • Quantum (loop) corrections? • What are its self-couplings?

  26. 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? Cutoff Λ = 10 TeV New technicolour force? • Heavy scalar resonance? • Inconsistent with precision electroweak data? Cut-off Λ ~ 1 TeV with Supersymmetry?

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

  28. General Analysis of ‘unHiggs’ Models • Parametrization of effective Lagrangian: • Fits c a ≠ c a CMS fit assuming c > 0 Azatov, Contino, Galloway: arXiv:1202.3415

  29. Global Analysis of Higgs-like Models • Rescale couplings: to bosons by a, to fermions by c • Standard Model: a = c = 1 Update from Kyoto CDF/D0 ATLAS Global CMS JE & Tevong You, arXiv:1204.0464 JE & Tevong You, arXiv:1207.1693

  30. What is it ? • Does it have spin 0 or 2? • Spin 2 seems unlikely, but needs experimental checks • Is it scalar or pseudoscalar? • Pseudoscalardisfavoured by experiment • Is it elementary or composite? • No significant deviations from Standard Model • Does it couple to particle masses? • Quantum (loop) corrections? • What are its self-couplings?

  31. It Walks and Quacks like a Higgs • Do couplings scale ~ mass? With scale = v? • Standard Model Higgs: ε = 0, M = v Global fit Update from Kyoto JE & Tevong You, arXiv:1207.1693

  32. It Walks and Quacks like a Higgs • Do couplings scale ~ mass? With scale = v? • Red line = SM, dashed line = best fit Global fit Update from Kyoto JE & Tevong You, arXiv:1207.1693

  33. What is it ? • Does it have spin 0 or 2? • Spin 2 seems unlikely, but needs experimental checks • Is it scalar or pseudoscalar? • Pseudoscalardisfavoured by experiment • Is it elementary or composite? • No significant deviations from Standard Model • Does it couple to particle masses? • Some prima facie evidence that it does • Quantum (loop) corrections? • What are its self-couplings?

  34. Loop Corrections ? • Experimental limits on anomaly coefficients • Anomalous triangle diagrams > Standard Model? Global fit JE, Sanz & You, arXiv:1211.3068

  35. What is it ? • Does it have spin 0 or 2? • Spin 2 seems unlikely, but needs experimental checks • Is it scalar or pseudoscalar? • Pseudoscalar disfavoured by experiment • Is it elementary or composite? • No significant deviations from Standard Model • Does it couple to particle masses? • Some prima facie evidence that it does • Quantum (loop) corrections? • γγ coupling > Standard Model? • What are its self-couplings?

  36. What is it ? • Does it have spin 0 or 2? • Spin 2 seems unlikely, but needs experimental checks • Is it scalar or pseudoscalar? • Pseudoscalar disfavoured by experiment • Is it elementary or composite? • No significant deviations from Standard Model • Does it couple to particle masses? • Some prima facie evidence that it does • Quantum (loop) corrections? • γγ coupling > Standard Model? • What are its self-couplings? Wait for HL-LHC …?

  37. 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

  38. 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

  39. What else is there? Supersymmetry

  40. Data • Electroweak precision observables • Flavour physics observables • gμ - 2 • Higgs mass • Dark matter • LHC MasterCode: O.Buchmueller, JE et al.

  41. Search with ~ 5/fb @ 8 TeV Jets + missing energy

  42. O. Buchmueller, R. Cavanaugh, M. Citron, A. De Roeck, M.J. Dolan, J.E., H. Flacher, S. Heinemeyer, G. Isidori, J. Marrouche, D. Martinez Santos, S. Nakach, K.A. Olive, S. Rogerson, F.J. Ronga, K.J. de Vries, G. Weiglein

  43. Measurements of Bs μ+μ- • LHCb finds ~ (1 ± 0.3) × Standard Model Update from Kyoto

  44. 1 5 --- 1/fb ___ 5/fb CMSSM With LHCb update from Kyoto Buchmueller, JE et al: arXiv:1207.3715 p-value of simple models < 10%

  45. 1 5 Gluino mass CMSSM With LHCb update from Kyoto Buchmueller, JE et al: arXiv:1207.3715 Favoured values of gluino mass significantly above pre-LHC, > 1.5 TeV

  46. 1 5 Bsμ+μ- CMSSM With LHCb update from Kyoto Buchmueller, JE et al: arXiv:1207.3715 Favoured values of close to Standard Model: Almost no change with new LHCb result

  47. XENON100 & other Experiments

  48. 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

  49. What remains for the CMSSM? Citron, JE, Luo, Marrouche, Olive, de Vries: arXiv:1212.2886 • Favoured regions of parameter space • Focus on the coannihilation strip • Small mass difference – long-lived stau?

  50. What remains for the CMSSM? • Stau lifetime sensitive to Δm, may be long • May decay inside or outside the detector • Decays into 1 or 3 charged particles, also neutrals Citron, JE, Luo, Marrouche, Olive, de Vries: arXiv:1212.2886

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