the higgs boson & beyond
DESCRIPTION
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? - PowerPoint PPT PresentationTRANSCRIPT
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The Higgs Boson & Beyond
To Higgs or not to Higgs?just one of the questions being studied at the LHC
John EllisKing’s College London
(& CERN)
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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
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Some Questions
• What is it?–Higgs or …?
• What else is there?–Supersymmetry or …?
• What next?–A Higgs factory or …?
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The Seminal Papers
The only one
who mentioned a
massive scalar boson
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A Phenomenological Profile of the Higgs Boson
• First attempt at systematic survey
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A Preview of the Higgs Boson @ LEP
• First LEP Yellow Report in 1976:– Higgsstrahlung “Bjorken process”
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A Preview of the Higgs Boson @ LHC
• Prepared for LHC Lausanne workshop 1984
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• First attempts in 1990,
• Easier after the discovery of the top quark
Estimating the Mass of the Higgs Boson
JE, Fogli & Lisi
1991
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Calculating the Mass of the Higgs Boson
Expensive – but maybe not my most costly calculation …
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2011: Combining Information from Previous Direct Searches and Indirect Data
mH = 125 ± 10 GeV Gfitter collaboration
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Higgs Production at the LHC
A la recherche du Higgs perdu …
Many production modes measurable if Mh ~ 125 GeV
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• Couplings proportional to masses (?)
• Important couplings through loops:– gluon + gluon → Higgs → γγ
Higgs Decay Branching Ratios
Many decay modes measurable if Mh ~ 125 GeV
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Higgsdependence Day!
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Unofficial Combination of Higgs Search Data from December 13th
Is this the
Higgs Boson?
No Higgs here!No
Higgs
here!
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The Particle Higgsaw Puzzle
Is LHC finding the missing piece?
Is it the right shape?
Is it the right size?
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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?
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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
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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
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• 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)
Does the ‘Higgs’ have Spin Two ?
JE, Sanz & You, arXiv:1211.3068
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• Fit of vector-boson couplings to spin-two model
• Prediction of AdS-type graviton-like model disfavoured by > 3 σ
Does the ‘Higgs’ have Spin Two ?
JE, Sanz & You, arXiv:1211.3068
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Does the ‘Higgs’ have Spin Two ?
• Discriminate spin 2 vs spin 0 via angular distribution of decays into γγ
JE, Fok, Hwang, Sanz & You: arXiv:1210.5229
JE & Hwang: arXiv:1202.6660
Monte Carlo simulations
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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%
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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?
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• Kinematic distribution of ZZ* final state
• 0- disfavoured @ 97% level
The ‘Higgs’ probably has Parity +
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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?
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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
New technicolour force?-Heavy scalar resonance?-Inconsistent with precision electroweak data?
Cut-off Λ ~ 1 TeV with
Supersymmetry?
Cutoff
Λ = 10 TeV
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Higgs as a Pseudo-Goldstone
Boson
Loop cancellation mechanism
SupersymmetryLittle Higgs
‘Little Higgs’ models
(breakdown of larger symmetry)
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General Analysis of ‘unHiggs’ Models
• Parametrization of effective Lagrangian:
• Fits
Azatov, Contino, Galloway: arXiv:1202.3415
a ≠ c
CMS fit assuming c > 0
c
a
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Global Analysis of Higgs-like Models
• Rescale couplings: to bosons by a, to fermions by c
• Standard Model: a = c = 1 JE & Tevong You, arXiv:1207.1693
JE & Tevong You, arXiv:1204.0464
CDF/D0ATLASCMSUpdate
from KyotoGlobal
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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?
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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
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It Walks and Quacks like a Higgs
• Do couplings scale ~ mass? With scale = v?
• Red line = SM, dashed line = best fitJE & Tevong You, arXiv:1207.1693
Global
fitUpdate
from Kyoto
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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?
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Loop Corrections ?
• Experimental limits on anomaly coefficients
• Anomalous triangle diagrams > Standard Model?
Global
fit
JE, Sanz & You, arXiv:1211.3068
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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?
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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 …?
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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 < 0at some scale Λ→ vacuum unstable
• Vacuum could be stabilized by SupersymmetryDegrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:1205.6497
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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
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What else is there?
Supersymmetry
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Data
• Electroweak precision observables
• Flavour physics observables
• gμ - 2
• Higgs mass
• Dark matter
• LHCMasterCode: O.Buchmueller, JE et al.
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Search with ~ 5/fb @ 8 TeV
Jets + missing energy
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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
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• LHCb finds ~ (1 ± 0.3) × Standard Model
Measurements of Bs μ+μ-
Update
from Kyoto
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5
--- 1/fb___ 5/fb
p-value of simple models < 10%
1
Buchmueller, JE et al: arXiv:1207.3715
With LHCb update
from Kyoto
CMSSM
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51
Favoured values of gluino mass significantly
above pre-LHC, > 1.5 TeV
Gluino mass
Buchmueller, JE et al: arXiv:1207.3715
CMSSM
With LHCb update
from Kyoto
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51
Favoured values of close to Standard Model:
Almost no change with new LHCb result
Bs μ+μ-
Buchmueller, JE et al: arXiv:1207.3715
CMSSMWith LHCb update
from Kyoto
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XENON100 & other Experiments
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Favoured values of dark matter scattering
cross section significantly below XENON100
5
--- 1/fb___ 5/fb
Buchmueller, JE et al: arXiv:1207.3715
Spin-independent
Dark matter scattering
Excluded by
XENON100
Excluded by LHC
2
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• Favoured regions of parameter space
• Focus on the coannihilation strip
• Small mass difference – long-lived stau?
What remains for the CMSSM? Citron, JE, Luo, Marrouche, Olive, de Vries: arXiv:1212.2886
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• Stau lifetime sensitive to Δm, may be long
• May decay inside or outside the detector
• Decays into 1 or 3 charged particles, also neutrals
What remains for the CMSSM?
Citron, JE, Luo, Marrouche, Olive, de Vries: arXiv:1212.2886
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• Small Δm favoured in χ2 analysis
• May decay inside or outside the detector
Search for long-lived Staus?
Citron, JE, Luo, Marrouche, Olive, de Vries: arXiv:1212.2886
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Conversation with Mrs Thatcher: 1982
What do you do?
Think of things for the experiments to look
for, and hope they find something different
Wouldn’t it be better if they
found what
you predicted?
Then we would not learn anything!
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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?
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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
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e+e- Collider Summary
ICFA Higgs Factory Workshop
Fermilab, Nov. 2012