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?
LHC
due to a Higgs boson?
• Why so many types of matter particles? LHC
• What is the dark matter in the Universe? LHC
• Unification of fundamental forces?
LHC
• Quantum theory of gravity?
LHC
Some Questions
• What is it?
–Higgs or …?
• What else is there?
–Supersymmetry or …?
• What next?
–A Higgs factory or …?
The Seminal Papers
The only one
who mentioned a
massive scalar boson
A Phenomenological Profile
of the Higgs Boson
• First attempt at systematic survey
A Preview of the Higgs Boson @ LEP
• First LEP Yellow Report in 1976:
–
Higgsstrahlung
“Bjorken process”
A Preview of the Higgs Boson @ LHC
• Prepared for LHC Lausanne workshop 1984
Estimating the Mass of the Higgs Boson
• First attempts in 1990, 1991
• Easier after the discovery of the top quark
JE, Fogli & Lisi
Calculating the Mass of the Higgs Boson
Expensive – but maybe
not my most costly
calculation …
2011: Combining Information from
Previous Direct Searches and Indirect Data
mH = 125 ± 10 GeV
Gfitter collaboration
A la
recherche du
Higgs perdu
…
Higgs Production at the
LHC
Many production modes measurable if Mh ~ 125 GeV
Higgs Decay Branching Ratios
• Couplings proportional to masses (?)
• Important couplings through loops:
– gluon + gluon → Higgs → γγ
Many decay modes measurable if Mh ~ 125 GeV
Higgsdependence Day!
Unofficial Combination of Higgs Search
Data from December 13th
Is this the
Higgs Boson?
No
Higgs
here!
No Higgs here!
The Particle Higgsaw Puzzle
Is LHC finding the missing piece?
Is it the right shape?
Is it the right size?
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?
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
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
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 JE, Sanz & You, arXiv:1211.3068
(Also expect vector mass < tensor mass X LHC)
Does the ‘Higgs’ have Spin Two ?
• Fit of vector-boson couplings to spin-two model
JE, Sanz & You, arXiv:1211.3068
• Prediction of AdS-type graviton-like model
disfavoured by > 3 σ
Does the ‘Higgs’ have Spin Two ?
• Discriminate spin 2 vs spin 0 via angular
JE & Hwang: arXiv:1202.6660
distribution of decays into γγ
Monte Carlo simulations
JE, Fok, Hwang, Sanz & You: arXiv:1210.5229
The ‘Higgs’ probably does not
have Spin Two
• ATLAS γγ analysis prefers spin 0 over 2+
2+ disfavoured @ 91%
• No discrimination from CMS ZZ* analysis
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?
The ‘Higgs’ probably has Parity +
• Kinematic distribution of ZZ* final state
• 0- disfavoured @ 97% level
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?
• Does it couple to particle masses?
• Quantum (loop) corrections?
• What are its self-couplings?
Elementary Higgs or Composite?
• Higgs field:
<0|H|0> ≠ 0
• Quantum loop problems
• Fermion-antifermion
condensate
• Just like QCD, BCS
superconductivity
Cutoff
Λ = 10 TeV • Top-antitop condensate?
needed mt > 200 GeV
Cut-off Λ ~ 1 TeV with
Supersymmetry?
New technicolour force?
- Heavy scalar resonance?
- Inconsistent with
precision electroweak data?
Higgs as a
Pseudo-Goldstone
Boson
‘Little Higgs’ models
(breakdown of larger symmetry)
Loop cancellation mechanism
Little Higgs
Supersymmetry
General Analysis of ‘unHiggs’
Models
• Parametrization of effective Lagrangian:
• Fits
c
a≠c
Azatov, Contino, Galloway: arXiv:1202.3415
CMS fit assuming c > 0
a
Global Analysis of Higgs-like Models
• Rescale couplings: to bosons by a, to fermions by c
Update
from Kyoto
Global
CDF/D
ATLAS
CMS
0
JE & Tevong You, arXiv:1204.0464
• Standard Model: a = c = 1
JE & Tevong You, arXiv:1207.1693
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?
• Quantum (loop) corrections?
• What are its self-couplings?
It Walks and Quacks like a Higgs
• Do couplings scale ~ mass? With scale = v?
Global
fit
Update
from Kyoto
JE & Tevong You, arXiv:1207.1693
• Standard Model Higgs: ε = 0, M = v
It Walks and Quacks like a Higgs
• Do couplings scale ~ mass? With scale = v?
Global
fit
Update
from Kyoto
JE & Tevong You, arXiv:1207.1693
• Red line = SM, dashed line = best fit
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?
• What are its self-couplings?
Loop Corrections ?
• Experimental limits on anomaly coefficients
Global
fit
JE, Sanz & You, arXiv:1211.3068
• Anomalous triangle diagrams > Standard Model?
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?
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 …?
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
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
What else is there?
Supersymmetry
Data
• Electroweak precision
observables
• Flavour physics
observables
• gμ - 2
• Higgs mass
• Dark matter
• LHC
MasterCode: O.Buchmueller, JE et al.
Search with ~ 5/fb @ 8 TeV
Jets + missing energy
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
Measurements of Bs  μ+μD c2
9
8
7
6
5
4
3
2
1
0
0
2
4
6
s
BR(B ® mm)[x10-9]
Update
from Kyoto
8
• LHCb finds ~ (1 ± 0.3) × Standard Model
1
3000
5
--- 1/fb
___ 5/fb
CMSSM
With LHCb update
from Kyoto
2000
0
5 .9 9 0
2 .3 0
m 1/ 2[GeV]
2500
1500
2 .3 0 0
5.990
1000
2.
30
0
500
0
0
1000
2000
m 0[GeV]
3000
4000
Buchmueller, JE et al: arXiv:1207.3715
p-value of simple models < 10%
1
Gluino mass
5
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
1
Bs μ+μ-
5
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
XENON100 & other Experiments
2
-40
10
-41
10
-42
10
-43
10
-44
10
-45
10
-46
10
-47
10
-48
Spin-independent
Dark matter scattering
Excluded by
XENON100
5 .9 9
0
1
10
2
m χ˜ 01 [GeV]
5 .9 9 0
5 .9 9 0
10
Excluded
by LHC
2.
30
2.3 00
5 .9 9 0
σpSI [cm 2 ]
--- 1/fb
___ 5/fb
10
5
0
10
3
Buchmueller, JE et al: arXiv:1207.3715
Favoured values of dark matter scattering
cross section significantly below XENON100
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?
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
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:1212.2886
Conversation with Mrs Thatcher: 1982
What do you do?
Think of things for the
experiments to look
for, and hope they find
something different
Then we would not
learn anything!
Wouldn’t it be
better if they
found what
you predicted?
The ‘Higgs Legacy’?
• Seize the moment to engage students, general
public, Government, ….
–
–
–
–
–
Local communities
Schools
Visits to CERN
Science centres
MPs
• ‘Higgs Day’ Nov. 7th 2013?
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
e+e- Collider Summary
ICFA Higgs Factory Workshop
Fermilab, Nov. 2012