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 EllisKing’s College London

(& CERN)

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

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

• First attempts in 1990,

• Easier after the discovery of the top quark

Estimating the Mass of the Higgs Boson

JE, Fogli & Lisi

1991

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

Higgs Production at the LHC

A la recherche du Higgs perdu …

Many production modes measurable if Mh ~ 125 GeV

• Couplings proportional to masses (?)

• Important couplings through loops:– gluon + gluon → Higgs → γγ

Higgs Decay Branching Ratios

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

• 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

• 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

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

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%

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?

• Kinematic distribution of ZZ* final state

• 0- disfavoured @ 97% level

The ‘Higgs’ probably has Parity +

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

• 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

Higgs as a Pseudo-Goldstone

Boson

Loop cancellation mechanism

SupersymmetryLittle Higgs

‘Little Higgs’ models

(breakdown of larger symmetry)

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

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

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?

• Standard Model Higgs: ε = 0, M = v

Global

fit

Update

from Kyoto

JE & Tevong You, arXiv:1207.1693

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

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

• Anomalous triangle diagrams > Standard Model?

Global

fit

JE, Sanz & You, arXiv:1211.3068

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 < 0at some scale Λ→ vacuum unstable

• Vacuum could be stabilized by SupersymmetryDegrassi, 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

• LHCMasterCode: 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

• LHCb finds ~ (1 ± 0.3) × Standard Model

Measurements of Bs μ+μ-

Update

from Kyoto

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

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

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

XENON100 & other Experiments

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

• 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

• 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

• 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

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!

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