Higgs, more Higgs, less Higgs, or Higgsless? John Ellis King’s College, London (& CERN)

Higgs, more Higgs, less Higgs, or Higgsless?

John Ellis

King’s College, London

(& CERN)

The ‘Standard Model’ of Particle Physics

Proposed byAbdus Salam, Glashow and Weinberg

Tested by experimentsat CERN & elsewhere

Perfect agreement betweentheory and experiments

in all laboratories

Open Questions beyond the Standard Model

• What is the origin of particle masses?

due to a Higgs boson?

• Why so many flavours of matter particles?

• What is the dark matter in the Universe?

• Unification of fundamental forces?

• Quantum theory of gravity?

LHC

LHC

LHC

LHC

LHC

Why do Things Weigh?

0

Where do the masses come from?

Newton:Weight proportional to Mass

Einstein:Energy related to Mass

Neither explained origin of Mass

Are masses due to Higgs boson? (the physicists’ Holy Grail)

The Seminal Papers

The Englert-Brout-Higgs Mechanism

Englert & Brout Guralnik, Hagen & Kibble

The Higgs Boson

• Higgs pointed out a massive scalar boson

• “… an essential feature of [this] type of theory … is the prediction of incomplete multiplets of vector and scalar bosons”

• Englert, Brout, Guralnik, Hagen & Kibble did not comment on its existence

• Discussed in detail by Higgs in 1966 paper

Mysterious Higgs Potential

Mass2 of Higgs ~ curvature of potential at minimum

Vertical scale ~ 1060 × dark energy

A Phenomenological Profile of the Higgs Boson

• Neutral currents (1973)

• Charm (1974)

• Heavy lepton τ (1975)

• Attention to search for W±, Z0

• For us, the Big Issue: is there a Higgs boson?

• Previously ~ 10 papers on Higgs bosons

• MH > 18 MeV

• First attempt at systematic survey

• Higgs decay modes and searches in 1975:

A Phenomenological Profile of the Higgs Boson

Higgs Boson placed on the Experimental Agenda

• Searches at LEP:(EG, Yellow report 76-

18)

• e+e- Z + H

(EGN 76, Ioffe & Khoze 76,

Lee, Quigg & Thacker 77)

• Z H + μ+μ-

(EG 76, Bjorken 1976)

• LEP: MH > 114.4 GeV

The State of the Higgs in Mid-2011

• High-energy search:– Limit from LEP:

mH > 114.4 GeV

• High-precision electroweak data:– Sensitive to Higgs mass:

mH = 96+30–24 GeV

• Combined upper limit:

mH < 161 GeV, or 190 GeV including direct limit

• Exclusion from high-energy search at Tevatron:

mH < 158 GeV or > 173 GeV

Latest Higgs Searches @ Tevatron

Exclude (100,109); (156,177) GeV

Standard Model

prediction

Experimental

upper limit

Higgs Hunting @ LHC: Status reported on Dec. 13th, 2011

Exclude 112.7 GeV to 115.5 GeV,

131 GeV to 237 GeV,

251 GeV to 453 GeV

Exclude 127 to 600 GeV

Has the Higgs Boson been Discovered?

Interesting hints around Mh = 125 GeV ?

CMS sees broadenhancement

ATLAS prefers125 GeV


Interesting hints around 125 GeV in both experiments- but could also be 119 GeV ?

ATLASSignals

• γγ: 2.8σ• ZZ: 2.1σ• WW: 1.4σ• Combined: 3.6σ

CMS Signals

• Combined: 2.6σ


Unofficial blogger’s combinationNOT ENDORSED BY EXPERIMENTS

but he was right last time !

Combining the Information from Previous Direct Searches and Indirect Data

mH = 125 ± 10 GeVErler: arXiv:1201.0695

mH = 124.5 ± 0.8 GeV

Assuming the Standard Model

Precision

Electroweakdata??Higgs

couplingblows up!!

Higgspotentialcollapses

Higgs coupling lessthan in Standard Model

viXra Blogger’s Combination of Dec.13th Data

There must be New PhysicsBeyond the Standard Model

Heretical Interpretation of EW Data

Do all the data tell the same story?e.g., AL vs AH

What attitude towards LEP, NuTeV?

What mostof us think

Chanowitz

Higgs + Higher-Order Operators

Precision EW data suggest they are small: why?

But conspiraciesare possible: mH

could be large, even if believeEW data …?

Do not discard possibility of heavy Higgs

Corridor toheavy Higgs?

Barbieri, Strumia

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? inconsistent with precision electroweak data? Cut-off Λ ~ 1 TeV with

Supersymmetry?

Cutoff Λ = 10 TeV

Interpolating Models

• Combination of Higgs boson and vector ρ

• Two main parameters: mρ and coupling gρ

• Equivalently ratio weak/strong scale:

gρ / mρ

Grojean, Giudice, Pomarol, Rattazzi

What if the Higgs is not quite a Higgs?

• Tree-level Higgs couplings ~ masses– Coefficient ~ 1/v

• Couplings ~ dilaton of scale invariance• Broken by Higgs mass term –μ2, anomalies

– Cannot remove μ2 (Coleman-Weinberg)– Anomalies give couplings to γγ, gg

• Generalize to pseudo-dilaton of new (nearly) conformal strongly-interacting sector

• Couplings ~ m/V (V > v?), additions to anomalies

A Phenomenological Profile of a Pseudo-Dilaton

• New strongly-interacting sector at scale ~ V• Pseudo-dilaton only particle with mass << V• Universal suppression of couplings to Standard

Model particles ~ v/V• Γ(gg) may be enhanced• Γ(γγ) may be suppressed• Modified self-couplings• Pseudo-baryons

as dark matter?

Compilationof constraints

Campbell, JE, Olive: arXiv:1111.4495

Updatedwith Dec. 11constraints

Higgsless Models?

• Four-dimensional versions:

Strong WW scattering @ TeV, incompatible with precision data?

• Break EW symmetry by boundary conditions in extra dimension:

delay strong WW scattering to ~ 10 TeV?

Kaluza-Klein modes: mKK > 300 GeV?

compatibility with precision data?• Warped extra dimension + brane kinetic terms?

Lightest KK mode @ few 00 GeV, strong WW @ 6-7 TeV

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 supersymmetryEspinosa, JE, Giudice, Hoecker, Riotto, arXiv0906.0954

LHC 95%exclusion

SUSY vs Data

• Electroweak precision observables

• Flavour physics observables

• gμ - 2

• Higgs mass

• Dark matter

• LHCMasterCode: O.Buchmueller, JE et al.

68% & 95% CL contours

….. pre-LHC___ LHC 1/fb

Favoured values of Mh ~ 119 GeV:Range consistent with evidence from LHC !

Higgs mass

χ2 price to pay if Mh = 125 GeV is < 2

Buchmueller, JE et al: arXiv:1112.3564

….. pre-Higgs___ Higgs @ 125



Favoured values of gluino mass significantlyabove pre-LHC, > 2 TeV

Gluino mass

--- pre-Higgs___ Higgs @ 125… H@125, no g-2


The Stakes in the Higgs Search

• How is gauge symmetry broken?• Is there any elementary scalar field?• Would have caused phase transition in the Universe when

it was about 10-12 seconds old• May have generated then the matter in the Universe:

electroweak baryogenesis• A related inflaton might have expanded the Universe

when it was about 10-35 seconds old • Contributes to today’s dark energy: 1060 too much!

Measurements of Higgs Couplings

• Some decays limited by statistics

• Others limited by systematics

The Spin of the Higgs Boson @ LHC

Higher mass: angular correlations in H → ZZ decays

Low mass: if H →γγ,It cannot have spin 1

Higgs Self-coupling @ Hi-Lumi LHC?

Measure triple-Higgs-boson coupling with

accuracy comparable to 0.5 TeV ILC?

Awaits confirmation by detailed experimental simulation

The Fun is just Beginning

• LHC7 may well resolve Higgs issue

• LHC7 (or 8) unlikely to resolve SUSY issue

(or other BSM scenarios)

• Premium on increasing Ecm towards 14 TeV

• Prospects for L factor 500 with Hi-Lumi LHC

• What will follow the LHC?– Higgs factory? CLIC? High-E LHC?

• A new era about to open: AH (anno Higgsi)

Quo Vadisgμ - 2?

• Strong discrepancy between BNL experiment and e+e- data:

– now ~ 3.6 σ

– Better agreement between

e+e- experiments

• Increased discrepancy between BNL experiment and τ decay data

– now ~ 2.4 σ

– Convergence between e+e-

experiments and τ decay

• More credibility?

MSSM: > 100 parametersMinimal Flavour Violation: 13 parameters

(+ 6 violating CP)

SU(5) unification: 7 parameters

NUHM2: 6 parameters

NUHM1 = SO(10): 5 parameters

CMSSM: 4 parametersmSUGRA: 3 parameters

String?

… nevertheless

Supersymmetric Dark Matter in View of 1/fb of LHC Data



MasterCode: O.Buchmueller, JE et al.

Dropping gμ - 2 allows masses up to dark matter limit


Impact of droppinggμ-2 constraint


Favoured values of gluino mass significantlyabove pre-LHC, > 1 TeV


Gluino mass


Favoured values of BR(Bs μ+μ-) above SM value !(due to increase in tan β)

+ LHCbBs μ+μ-

….. pre-LHC___ LHC 1/fb--- with CDF


Favoured values of Mh ~ 119 GeV:Coincides with value consistent with LHC !

Higgs mass

Generic LittleHiggs Models

Loop cancellation mechanism

SupersymmetryLittle Higgs

(Higgs as pseudo-Goldstone

boson of larger symmetry)

Little Higgs Models

• Embed SM in larger gauge group• Higgs as pseudo-Goldstone boson• Cancel top loop

with new heavy T quark

• New gauge bosons, Higgses• Higgs light, other new

physics heavyNot as complete as susy: more physics > 10 TeV

MT < 2 TeV (mh / 200 GeV)2

MW’ < 6 TeV (mh / 200 GeV)2

MH++ < 10 TeV

Searches for Extra Particles in

Little Higgs Models

Spread looks natural: no significant disagreement

Estimates of mH from different Measurements

Intermediate Models

Effects on Higgs Decays

• Dependences on of Higgs branching ratios

• Standard Model recovered in limit 0

Grojean, Giudice, Pomarol, Rattazzi

What if no Higgs?

• Higgs must discriminate between different types of particles:– Some have masses, some do not– Masses of different particles are different

• In mathematical jargon, symmetry must be broken: how?– Break symmetry in equations?– Or in solutions to symmetric equations?

• This is the route proposed by Higgs– Is there another way?

Where to Break the Symmetry?

• Throughout all space?– Route proposed by Higgs– Universal Higgs (snow)field breaks symmetry– If so, what type of field?

• Or at the edge of space?– Break symmetry at the boundary?

• Not possible in 3-dimensional space– No boundaries– Postulate extra dimensions of space

• Different particles behave differently in the extra dimension(s)

Higgs Hunting @ Tevatron

Exclude (100,109); (156,177) GeV

Comparison between Weakly- and Strongly-coupled Models

XENON100 & other Experiments

Aprile et al: arXiv:1104.2549

Supersymmetry Searches in ATLAS

Jets + missing energy + 0 lepton

XENON100 Experiment

Aprile et al: arXiv:1104.2549

Early Phenomenological Bounds

• Emission from stars:

MH > 0.7 me (Sato & Sato, 1975)

• Neutron-electron scattering:

MH > 0.7 MeV (Rafelski, Muller, Soff & Greiner;

Watson & Sundaresan; Adler, Dashen & Treiman; 1974)

• Neutron-nucleus scattering:

MH > 13 MeV (Barbieri & Ericson, 1975)

• Nuclear 0+ – 0+ transitions:

MH > 18 MeV (Kohler, Watson & Becker, 1974)

Supersymmetry Searches @ LHC

Jets + missing energy (+ lepton(s))

Applicable to NUHM, CMSSM, VCMSSM, mSUGRA

but need other strategies for other models

Higgs, more Higgs, less Higgs, or Higgsless? John Ellis King’s College, London (& CERN)

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