TheGodParticleForAtheists SNU

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The God Particle for Atheists and Agnostics The God Particle for Atheists and Agnostics Vikram Vyas 18 November 2013

Transcript of TheGodParticleForAtheists SNU

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The God Particle for Atheists and Agnostics

The God Particle for Atheists and Agnostics

Vikram Vyas

18 November 2013

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The God Particle for Atheists and Agnostics

Outline

1 Caveat

2 The Standard Model

3 The Electro-Weak Interactions

4 The Beauty of the Local Symmetry

5 Problem in the Paradise

6 Higgs is Hiding the Symmetry

7 Higgs Particle: Making Waves in Vacuum

8 More Things Under the Heaven

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Caveat

Caveat

However, this does not mean that I have tried to write an easybook ... I picture the reader as a smart old attorney who doesnot speak my language, but who expects none the less to hearsome convincing arguments before he makes up his mind.Steven Weinberg (Introduction to First Three Minutes)The complement of truth is clarity. Truth and clarity arecomplementary.Neils Bohr

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The God Particle for Atheists and Agnostics

The Standard Model

Inward Bound

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The God Particle for Atheists and Agnostics

The Standard Model

The Standard Model

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The Electro-Weak Interactions

Light: The Electromagnetic Interaction

The way we see the world.Long range - we can see almost to the edge of the universe.Mirror world is a possible world.The force carrier is the photon: A massless particle

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The Electro-Weak Interactions

Weak Interaction

It is short range - relevant only when particles are at distanceof the order of nuclear sizes.It is responsible for radioactivity.Mirror world is NOT A POSSIBLE WORLD.The force carrier are massive particles.

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The Electro-Weak Interactions

Some examples of weak interaction

Scattering of neutrinos from proton

νe + p → νe + p

Scattering of electron from proton

e + p → νe + n

Decay of neutronn → p + e + ν̄e

Nuclear Fusion

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The Beauty of the Local Symmetry

The Photon

A particle with zero mass.It has two helicity or polarization.

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The Beauty of the Local Symmetry

Quantum Field Theory

Mathematical language to describe creation and annihilation ofidentical particles.With each fundamental particle we associate a set of numbersat each point in space which change with timeAll these numbers together called a field.

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The Beauty of the Local Symmetry

QED: The Quantum Theory Photons

What is the Quantum Field For Photons?

We need two numbers at each point for describing two typesof photons.But such a theory would lead to a description which wouldgive different laws of nature for differs observers.We add two redundant numbers so at each point of space wehave four numbers describing photons.

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The Beauty of the Local Symmetry

Redundancy is Symmetry

Symmetry

By symmetry we mean that there is some thing we can do to anobject such that after having done that the object still looks thesame.

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The Beauty of the Local Symmetry

Local Symmetry of QED

In QED the symmetry is that we can add redundant numbersto a given field and still the corresponding field would describethe same situation as the one described by the original field.Further these number can be different at different points ofspace and time, and so we say that the symmetry is local.

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The Beauty of the Local Symmetry

Gauge Symmetry = Massless Particle

Theorem

A quantum field theory which has local gauge symmetry describesmassless particles like photons.

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The Beauty of the Local Symmetry

The Beauty of the Local Symmetry

In 1950-60s many physicist realized that one can extend theidea of local symmetry from photon field to other fields.Such theories are called Yang-Mills theory.One of the simplest such extension would describe four photonlike particles, in that they are massless and have twopolarizations.

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The Beauty of the Local Symmetry

The Electro-Weak Unification

One of the particle behaves just like photon.It turns out that the way other three particles interacted withelectron and quarks could precisely describe the weakinteractions between them and these, then hypotheticalparticles, were called Z0, W+, W−.This was the electro-weak unification!

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Problem in the Paradise

Massless Particles = Long Range Force

Faraday’s Field Lines

Force goes as inverse square law - never becomeszero!

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Problem in the Paradise

Problem in the Paradise - 1

We have a problem!

If the weak interaction is described by Yang-Mills theory then weakinteraction cannot be a short range force.

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Problem in the Paradise

Weak World is not a Mirror World

If electron is massless then it comes in two varieties

Left Hand of Weak Interaction

Weak interaction requires eL carries weak charge and er has noweak charge.

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Problem in the Paradise

Problem in the Paradise - 2

We have a problem!

If weak interaction is described by Yang-Mills theory then electronand quarks must be massless.

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Higgs is Hiding the Symmetry

Vacuum is Not Nothing: Mexican Hat

Weinberg-Salam Model

Electromagnetic and weak interactions are described by aYang-Mills theory in which there is an additional field, the Higgsfield, which has two important properties

It carries weak charge.It has non-zero value in the ground state of the theory.

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Higgs is Hiding the Symmetry

Symmetric Theory Asymmetric Vacuum

Hiding the Symmetry

The universe is immersed in a field that carries weak charge - this isthe Higgs field.

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Higgs is Hiding the Symmetry

Curious Properties of Quantum Vacuum

Electro-Weak Vacuum

The vacuum has indefinite amount of weak charge.It has no electric charge.The weak charges (and field lines) can disappear into thevacuum.

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Higgs is Hiding the Symmetry

Higgs+Faraday:Massive Gauge Bosons

Since the vacuum caries weak charge, the field-lines of weakcharge can disappear in vacuum.Weak-force can become zero - has finite range - thecorresponding particle is massive!

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Higgs is Hiding the Symmetry

Dirac:Massive Electrons

Dirac Electron

A massive electron oscillates between left-handed electron andright-handed electron.

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Higgs is Hiding the Symmetry

Dirac+Higgs: Massive Electron from Massless Electron

A massless left handed electron can interact with the Higgsfield and get converted into a massless right handed electronwithout violating conservation of charge and becomes amassive particle.

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Higgs Particle: Making Waves in Vacuum

The Higgs Particle: That God Damm Particle

If the universe is immersed in Higgs field then we should beable to create waves in this medium.The quanta of this wave should be a particle - the Higgsparticle.

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Higgs Particle: Making Waves in Vacuum

Producing and Detecting Higgs Particle: The TheoristCartoon

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Higgs Particle: Making Waves in Vacuum

Higgs in LHC

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More Things Under the Heaven

Why these Masses?

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More Things Under the Heaven

Where is the Dark Matter?

The Unfinished Journey

The motion of stars in galaxies tell us that the our Universemust contain other types of particles which interact throughgravity but are not part of the standard model. This is the socalled “dark matter.”Therefore we know that the standard-model is incomplete.What are those new particles and interactions? We hope LHCwill provide us the with clues to them, and so we wait for LHCto start again!