Beyond the Higgs Boson John Ellis The Higgs is just one of the - - PowerPoint PPT Presentation

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Beyond the Higgs Boson John Ellis The Higgs is just one of the - - PowerPoint PPT Presentation

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Beyond the Higgs Boson John Ellis The Higgs is just one of the questions King s College London being studied at the LHC (& CERN) Beyond the Higgs Boson John Ellis The Higgs is just one of the questions King s College London being

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Beyond the Higgs Boson

The Higgs is just one of the questions

being studied at the LHC

John Ellis King’s College London (& CERN)

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Beyond the Higgs Boson

The Higgs is just one of the questions

being studied at the LHC

John Ellis King’s College London (& CERN)

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The ‘Standard Model’ of Particle Physics

Proposed byAbdus Salam, Glashow and Weinberg Tested by experiments at CERN Perfect agreement between theory and experiments in all laboratories

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The matter particles

The ‘Standard Model’

The fundamental interactions

Gravitation electromagnetism weak nuclear force strong nuclear force

= Cosmic DNA Where does mass come from?

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Summary of the Standard Model

  • Particles and SU(3) × SU(2) × U(1) quantum numbers:
  • Lagrangian:

gauge interactions matter fermions Yukawa interactions Higgs potential Now direct evidence

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Status of the Standard Model

  • Perfect agreement with all confirmed

accelerator data

  • Consistency with precision electroweak data

(LEP et al) only if there is a ‘Higgs boson’

  • Agreement seems to require a relatively light

Higgs boson weighing < ~ 180 GeV

  • Raises many unanswered questions:

mass? flavour? unification?

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Combining the Information from Direct Searches and Indirect Data

mH = 125 ± 10 GeV

Gfitter collaboration

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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 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

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At what Energy is the New Physics?

A lot accessible to the LHC Some accessible only via astrophysics & cosmology Dark matter Origin of mass

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Why do Things Weigh?

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)

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Think of a Snowfield

Skier moves fast: Like particle without mass e.g., photon = particle of light Snowshoer sinks into snow, moves slower: Like particle with mass e.g., electron Hiker sinks deep, moves very slowly: Particle with large mass The LHC will look for the snowflake: The Higgs Boson

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Introduction

Standard Model Particles:

Years from Proposal to Discovery

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The (NG)AEBHGHKMP Mechanism

The only one who mentioned a massive scalar boson

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Nambu EB, GHK and Higgs

Spontaneous symmetry breaking: massless Nambu- Goldstone boson ‘eaten’ by gauge boson ‘eaten’ by gauge boson

Accompanied by massive particle

EB, GHK

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A Phenomenological Profile

  • f the Higgs Boson
  • First attempt at systematic survey
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A Simulated Higgs Event @ LHC

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Astronomers tell us that most of the matter in the universe is invisible We will look for it with the LHC

Dark Matter in the Universe

Astronomers say that most of the matter in the Universe is invisible Dark Matter ‘Supersymmetric’ particles ? We shall look for them with the LHC

Dark Matter in the Universe

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Classic Dark Matter Signature

Missing transverse energy carried away by dark matter particles

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General Interest in Antimatter Physics

Physicists cannot make enough for Star Trek or Dan Brown!

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How do Matter and Antimatter Differ?

Dirac predicted the existence of antimatter: same mass

  • pposite internal properties:

electric charge, … Discovered in cosmic rays Studied using accelerators Matter and antimatter not quite equal and opposite: WHY? Why does the Universe mainly contain matter, not antimatter?

Experiments at LHC and elsewhere looking for answers

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How to Create the Matter in the Universe?

  • Need a difference between matter and antimatter
  • bserved in the laboratory
  • Need interactions able to creat matter

present in unified theories not yet seen by experiment

  • Must break thermal equilibrium

Possible in the decays of heavy particles

Sakharov Will we be able to calculate using laboratory data?

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300,000 years 3 minutes 1 micro- second 1 pico- second Formation

  • f atoms

Formation

  • f nuclei

Formation

  • f protons

& neutrons Appearance

  • f mass?

Appearance

  • f dark matter?

Appearance

  • f matter?
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 … but he never succeeded

Unification via extra dimensions of space?

Unify all the Fundamental Interactions: Einstein’s Dream …

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Would vanish instantly Eat up the entire Earth? Will LHC experiments create black holes?

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The Large Hadron Collider (LHC)

Proton- Proton Collider 7 TeV + 7 TeV

1,000,000,000 collisions/second

Primary targets:

  • Origin of mass
  • Nature of Dark Matter
  • Primordial Plasma
  • Matter vs Antimatter

Also collisions of Lead ions

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Vista General del LHC y sus Experimentos

27km in circumference ~ 100m deep

General View of LHC & its Experiments

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ATLAS: Higgs and supersymmetry CMS: Higgs and supersymmetry ALICE: Primordial cosmic plasma LHCb: Matter-antimatter difference

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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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Is the Higgs Boson finally being Revealed?

Mass Higgsteria

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Interesting Events

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July 4th 2012 The discovery of a new particle

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Higgsdependence Day!

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How the Higgs Signal has Grown

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Unofficial Combination of Higgs Search Data from March 6th

Is this the Higgs Boson? No Higgs here! No Higgs here!

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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 < 0 at some scale Λ → vacuum unstable

  • Vacuum could be stabilized by Supersymmetry

Degrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:1205.6497

Instability @ 1010 – 1013 GeV

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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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The Particle Higgsaw Puzzle

Is LHC finding the missing piece? Is it the right shape? Is it the right size?

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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?

e.g., cutoff Λ = 10 TeV

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Higgs as a Pseudo-Goldstone Boson

Loop cancellation mechanism Supersymmetry Little Higgs ‘Little Higgs’ models (breakdown of larger symmetry)

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Couplings resemble Higgs of Standard Model

  • No indication of any significant deviation from

the Standard Model predictions

JE & Tevong You, arXiv:1303.3879

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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:1303.3879

b bbar τ τ γ γ W W Z Z Global

No evidence for deviation from SM

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It Walks and Quacks like a Higgs

  • Do couplings scale ~ mass? With scale = v?
  • Red line = SM, dashed line = best fit

JE & Tevong You, arXiv:1303.3879

Global fit

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[1] = JE & Tevong You, arXiv:1303.3879

Dixit Swedish Academy

Today we believe that “Beyond any reasonable doubt, it is a Higgs boson.” [1]

http://www.nobelprize.org/nobel_prizes/physics/laureates/2013/a dvanced-physicsprize2013.pdf

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Without Higgs …

… there would be no atoms

– massless electrons would escape at the speed of light

… there would be no heavy nuclei … weak interactions would not be weak

– Life would be impossible: everything would be radioactive

Its existence is a big deal!

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What else is there?

Supersymmetry

  • Successful prediction for Higgs mass

– Should be < 130 GeV in simple models

  • Successful predictions for Higgs couplings

– Should be within few % of SM values

  • Could explain the dark matter
  • Naturalness, GUTs, string, … (???)
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“Classic” missing-energy search

Searches ~ 5/fb @ 8 TeV Searches with 8 TeV Data

Multiple searches including b, leptons

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p-value of simple models < 10%

2012

20/fb

Scan of CMSSM

Update of Buchmueller et al: arXiv:1207.3715

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5

1

20/fb

2012

CMSSM

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

Update of Buchmueller, JE et al: arXiv:1207.3715

Gluino mass Reach of LHC at High luminosity

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5

1

χ2

20/fb

2012

CMSSM

Favoured values of squark mass: ~ 2000 GeV or more

Update of Buchmueller, JE et al: arXiv:1207.3715

Squark mass Reach of LHC at High luminosity

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A Vision for the 21st Century

350 GeV Circular e+e- collider 100 TeV proton-proton collider

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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 so much!