1. Higgser ou ne pas Higgser ?
Ce n’est qu’une des questions étudiées au 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? What else is there? What next? Higgs or …?
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 @ LHC
Prepared for LHC Lausanne workshop 1984

7. 2011: Combining Information from Previous Direct Searches and Indirect Data
mH = 125 ± 10 GeV
Gfitter collaboration

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

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

10. Higgsdependence Day!

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

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

13. 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?

14. 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

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

16. 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:

17. 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:

18. Does the ‘Higgs’ have Spin Two ?
Discriminate spin 2 vs spin 0 via angular distribution of decays into γγ
JE & Hwang: arXiv:
Monte Carlo simulations
JE, Fok, Hwang, Sanz & You: arXiv:

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

20. What is it ? Does it have spin 0 or 2? Is it scalar or pseudoscalar?
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?

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

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

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

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

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

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

27. What is it ? Does it have spin 0 or 2? Is it scalar or pseudoscalar?
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?
Quantum (loop) corrections?
What are its self-couplings?

28. 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:

29. 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:

30. What is it ? Does it have spin 0 or 2? Is it scalar or pseudoscalar?
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?
What are its self-couplings?

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

32. What is it ? Does it have spin 0 or 2? Is it scalar or pseudoscalar?
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?

33. What is it ? Does it have spin 0 or 2? Is it scalar or pseudoscalar?
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 …?

34. 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:

35. 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:

36. What else is there?
Supersymmetry

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

38. Search with ~ 8 TeV
Jets + missing energy 38

39. 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

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

41. Favoured values of gluino mass significantly1 5
Gluino mass
CMSSM
With LHCb update
from Kyoto
Buchmueller, JE et al: arXiv:
Favoured values of gluino mass significantly
above pre-LHC, > 1.5 TeV

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

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

44. 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:

45. Search for long-lived Staus?
Small Δm favoured in χ2 analysis
May decay inside or outside the detector
Citron, JE, Luo, Marrouche, Olive, de Vries: arXiv:

46. 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

47. ICFA Higgs Factory Workshop
e+e- Collider Summary
Best
precision
ICFA Higgs Factory Workshop
Fermilab, Nov. 2012

48. Circular e+e- Colliders
FNAL
Blondel JE et al: arXiv:

49. Photon-Photon Colliders
Bogacz, JE et al: arXiv:

50. Muon Collider

51. Conversation with Mrs Thatcher: 1982
What do you do?
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
Then we would not learn anything!