Linear ColliderHitoshi Murayama (Berkeley)EPP2010@SLAC, Jan 31, 2005

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Take-home messages

•We are approaching a new layer of energy scale: something is brewing at TeV-scale

•Solutions to many deep puzzles hinge on what we find at this energy scale

•multiple tools needed to get a complete picture

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Outline

•Brief Recap of Science

•Need for Multiple Tools

•Dark Field=Cosmic Superconductor

•Linear Collider

Brief Recap of Science

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Energy budget of Universe

•Stars and galaxies are only ~0.5%

•Neutrinos are ~0.1–1.5%

•Rest of ordinary matter

•(electrons, protons & neutrons) are 4.4%

•Dark Matter 23%

•Dark Energy 73%

•Anti-Matter 0%

•Dark Field (Higgs) ~1062%??

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Einstein’s Dream•Is there an underlying

simplicity behind vast phenomena in Nature?

•Einstein dreamed to come up with a unified description

•But he failed to unify electromagnetism and gravity (GR)

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History of Unification

gravity

electric magnetic

α-decay

-decay

-decay

planets apple electromagnet

ism

atoms

Quantum mechanics

mechanics

Special relativityQuantum ElectroDynamics

Weak force

Strong Force

Electroweak theory

GR

String theory? Grand Unification?

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deeper into the heart of the

matter (literally)

My son on Halloween!Einstein?

increase resolution

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resolution=energy

•Quantum Mechanics: particle=wave

•higher energy

•= shorter wavelength

•= better resolution

low energy

high energy

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a new layer of unification

•Unification of electromagnetic and weak forces

⇒electroweak theory

•Long-term goal since ‘60s

•We are finally getting there!

•If they are unified, what makes them so different?

⇒Dark Field!

HERA ep collider

EM

weak

electromagnet

ism

weak

inflation

unificationstringanti-matter

Need for Multiple Tools

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Multiple Wavebands

in Astronomy

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Evidence forDark Matter

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Galaxies are held together by mass far bigger than all stars combined

Radiovisible

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•Yet another tool: cosmic microwave background

•matter/all atoms=6.03±0.03

•Dominant paradigm:

•Stable heavy particle produced in early Universe (E=mc2!)

•left-over from near-complete annihilation

•TeV: the correct temperature to produce them

Dark Matter is not atoms

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Telescopes vs Accelerators

aim need telescopes acceleratorsprobe deeper

better resolution

better mirrors, CCD

higher energy

better imagebetter

exposure

larger telescopes, more time

more powerful beams

(luminosity)

full understandi

ng

multiple probes

visible, radio, X-ray,

infrared, UV, gamma

protons, electrons, neutrinos

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Strong Force•Back to 1930s•atomic nuclei made of

protons and neutrons•why don’t protons

repel each other and nuclei disintegrate?

•a new mysterious “strong force” binding them together

•range of the force 0.000001 nanometer

•need 100 MeV to study

Yukawa predicted the force carrier whose mass is 100 MeV in 1933

discovered in 1947 (140 MeV)case closed?

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Strong Force•It was rather just

the beginning

•Soon proliferation of strongly-interacting particles at proton-based machines

•a big mess! (i.e. fun)

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Obstruction to Cosmology

•S. Weinberg “Gravitation and Cosmology” (1972)

•15.11 The Very Early Universe• If we look back into the first 0.0001 sec of cosmic history,

we encounter theoretical problems. At such temperatures copious number of strongly interacting particles will be in a state of continual mutual interaction and cannot reasonably be expected to obey any simple equation of state.

•There are two extremely different simple models that reflect two divergent views of the nature of the strongly interacting particles. Neither model can be taken seriously.

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Electron scattering•electron proton

scattering experiment

•looked dumb because electrons don’t do the strong force

•clear roles:

•electron=probe

•proton=object

•found that protons have constituents: “quarks”

•1990 Nobel:

•Friedman, Kendall, Taylor

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electron positron collider

can see quarks and a gluon ~19802004 Nobel to Gross, Wilczek, Politzer

Dark Field =cosmic

superconductor

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Mystery ofthe “weak force”•Gravity pulls two

massive bodies (long-ranged)

•Electric force repels two like charges (long-ranged)

•“Weak force” pulls protons and electrons (short-ranged) acts only over 0.000000001 nanometer

•[need it for the Sun to burn!]

•We know the energy scale: 0.3 TeV

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We are swimming in Dark Field

•There is something filling our Universe

•It doesn’t disturb gravity or electric force

•It does disturb weak force and make it short-ranged

•It slows down all elementary particles from speed of light

•What is it??•Extremely bizarre

theory!

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Cosmic Superconductor• In a superconductor, magnetic field gets repelled

(Meißner effect), and penetrates only over the “penetration length”

• ⇒ Magnetic field is short-ranged!

• Imagine a physicist living in a superconductor

•She finally figured:

•magnetic field must be long-ranged

• there must be a mysterious charge-two “Dark Field” in her “Universe”

•But doesn’t know what the Dark Field is, nor why it is there

•Doesn’t have enough energy (gap) to break up Cooper pairs

• That’s the stage where we are!

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Kick out Dark Field from the vacuum

•We know the energy scale of the problem:

•0.3 TeV

•pump energy into empty space to kick out whatever makes Dark Field: “Higgs boson”

•LHC will find it!!!!!

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Better be sure•For something this bizarre, we’d better

make sure

•Is the particle discovered really the Higgs boson?

•Is it really responsible for particle masses?

•Does this have the right properties?

•Is it really stuck in our Universe?

•Need detailed measurements for the proof

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Post-Higgs Problem

•We see “what” is stuck in our universe

•But we still don’t know “why”

•Two problems:

Why anything is stuck at all

Why is the scale of Dark Field 0.3TeV much much smaller than the scale of gravity ~1015 TeV

•Explanation most likely to be at ≤TeV scale because this is the relevant energy scale

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Three Directions•History repeats itself•discovery of anti-matter doubled #particles•Double #particles again ⇒ supersymmetry

•Learn from Cooper pairs again•Cooper pairs composite made of two electrons•Higgs boson may be pairwise composite • ⇒ technicolor

•Physics as we know it ends at TeV•Ultimate scale of physics: quantum gravity•May have quantum gravity at TeV • ⇒ hidden dimensions (0.01 cm to 10–17 cm)

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•Higgs boson as a Pseudo-Nambu-Goldstone boson (Little Higgs)

•Higgs boson as an extra-dimensional gauge boson (Gauge-Higgs Unification)

•Fat Higgs (Composite)

•Higgsless and W± as Kaluza-Klein boson

•technicolorful supersymmetry

More Directions

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Task•Why is there Dark Field?

•We can eliminate many possibilities at LHC

•But new interpretations necessarily emerge

•Race will be on:

•theorists coming up with new interpretations

•experimentalists excluding new interpretations

⇒A loooong process of elimination

•Crucial information is in details

⇒Reconstruct the theory from measurements

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Need absolute confidence for a major

discovery

•still a long way to

•“Halliday-Resnick” level confidence

•“We have learned that all particles we observe have unique partners of different spin and statistics, called superpartners, that make our theory of elementary particles valid to small distances.”

As an example, supersymmetry

“New-York Times level” confidence

inflation

unificationstringanti-matter

InternationalLinear Collider

(ILC)

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ILC

•electron position collider at 0.5-1 TeV

•about 20 miles long•super-high-tech: nanometer beams

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ILC

•elementary particles

•well-defined energy, angular momentum

•uses its full energy

•can produce particles democratically

•can capture nearly full information

LHC

ILC

pp

e+ e-

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ILC•superconducting

cavities for main accelerator

•technology is extremely challenging, yet basically at hand

•world-wide design in development

•need to complete the design (a real work!)

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LHC vs ILC(oversimplified)

total energy 14TeV 0.5-1 TeV

usable energy a fraction full

beamproton

(composite)electron (point-

like)

signal rate high low

noise rate very high low

analysis specific modes nearly all modes

eventslose info along

the beamscapture the

whole

statusunder

constructionneeds to finish

design

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Take-home messages

•We are approaching a new layer of energy scale: something is brewing at TeV-scale

•Solutions to many deep puzzles hinge on what we find at this energy scale

•multiple tools needed to get a complete picture

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In the Next Talk:•See how ILC, together with LHC

•can establish Higgs generates all masses

•can establish supersymmetry

•can test unification

•can figure out what Dark Matter is

•can study extra dimensions, measure their number, shape, geometry