Future Directions in Experimental Nuclear and Particle Physics

Barry BarishBacher Symposium

Caltech 5-Nov-05

Bacher at the Caltech Synchrotron

Robert Bacher

5-Nov-05 Bacher Symposium 2

Bacher and the Energy Frontier

• In the Spring of 1949, the Institute announced plans to build a one-billion volt ("1 BeV") electron accelerator.

• Robert Bacher, chairman of Caltech's Physics Division, stated: "The purpose of the new accelerator will be to seek additional knowledge about the nature of the forces that hold atomic nuclei together." The new accelerator, the synchrotron, would be the most powerful machine of its type ever built.

5-Nov-05 Bacher Symposium 3

Photoproduction of Excited States of the Nucleon

Bacher

5-Nov-05 Bacher Symposium 4

This led to higher energy machines: Electron-Positron Colliders

Bruno Touschek built the first successful electron-positron collider at Frascati, Italy (1960) with help from Bob Walker (Caltech) and others

Eventually, went up to 3 GeV

ADA

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But, not quite high enough energy ….

DiscoveryOf

CharmParticles

and

3.1 GeV

Burt RichterNobel Prize

SPEAR at SLAC

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The rich history for e+e- continued as higher energies were achieved …

DESY Petra Collider

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Electron Positron CollidersThe Energy Frontier

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The FutureThree Complementary Probes

• Neutrinos as a Probe– Particle physics and astrophysics using a weakly

interacting probe

• High Energy Proton Proton Colliders– Opening up a new energy frontier ( ~ 1 TeV scale)

• High Energy Electron Positron Colliders– Precision Physics at the new energy frontier

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What makes the sun shine?

4 1H 4He + 2e+ + 2 ve + energy

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Neutrinos observed from the sun !

Davis and Bahcall

Koshiba

Superkamiokande

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But, too few neutrinos …

If neutrinos have mass, then as conjectured earlier by Bruno Pontecorvo, neutrinos could “oscillate” from one type to another.

In this case, some of the original electron neutrinos made in the sun convert to other neutrinos on trajectory to the earth

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Puzzle resolved … neutrinos oscillate

SNO (Canada) used D20 to detect other neutrino types

KamLAND used terrestrialneutrinos from reactors,

observes oscillations (McKeown)

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Neutrinos – The Future

• Long baseline neutrino experiments – Create neutrinos at an accelerator or reactor and study at long distance when they have oscillated from one type to another.

MINOS

C Peck, H Newman, D Michael

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Neutrinos – The Big Questions

• Why are neutrino masses so small ? • Are the neutrinos their own antiparticles?• What is the separation and ordering of the

masses of the neutrinos?• Neutrinos contribution to the dark matter?

• CP violation in neutrinos, leptogenesis, possible role in the early universe and in understanding the particle antiparticle asymmetry in nature?

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Accelerators and the Energy FrontierLarge Hadron Collider

CERN – Geneva Switzerland

H Newman, E Hughes

5-Nov-05 Bacher Symposium 16

Accelerators and the Energy Frontier

International Linear Collider

B Barish

5-Nov-05 Bacher Symposium 17

Why e+e- Collisions ?

• elementary particles

• well-defined

– energy,

– angular momentum

• uses full COM energy

• produces particles democratically

• can mostly fully reconstruct events

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Electroweak Precision Measurements

What causes mass??

0

2

4

6

10020 400

mH GeV

Excluded Preliminary

had =(5)

0.027610.00036

0.027470.00012

Without NuTeV

theory uncertainty

Winter 2003

The mechanism – Higgs or alternative appears around the corner

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The linear collider will measure the spin of any Higgs it can produce by measuring the energy dependence from threshold

How do you know you have discovered the Higgs ?

Measure the quantum numbers. The Higgs must have spin zero !

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What can we learn from the Higgs?

•Straight blue line gives the standard model predictions.

• Range of predictions in models with extra dimensions -- yellow band, (at most 30% below the Standard Model

• The red error bars indicate the level of precision attainable at the ILC for each particle

Precision measurements of Higgs coupling can reveal extra dimensions in nature

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New space-time dimensions can be mapped by studying the emission of gravitons into the extra dimensions, together with a photon or jets emitted into the normal dimensions.

Linear collider

Direct production from extra dimensions

?

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Is there a new symmetry in nature?

SupersymmetryThe breaking of the symmetry between electromagnetic and weak interactions though the Higgs mechanism introduces several anomalies, which point towards physics beyond the standard model.

A particularly attractive scenario is supersymmetry (SUSY), which would eliminates the anomalies from the Higgs section and predicts SUSY partners for all known particles.

These particles should be detected at the LHC and ILC

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main linacbunchcompressor

dampingring

source

pre-accelerator

collimation

final focus

IP

extraction& dump

KeV

few GeV

few GeVfew GeV

250-500 GeV

Designing a Linear Collider

Superconducting RF Main Linac

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Superconducting RF Cavities

High Gradient Accelerator35 MV/meter -- 40 km linear collider

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Improved ProcessingElectropolishing

Chemical Polish

Electro Polish

Internationl Linear Collider Timeline

2005 2006 2007 2008 2009 2010

Global Design Effort Project

Baseline configuration

Reference Design

ILC R&D Program

Technical Design

Expression of Interest to Host

International Mgmt

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Conclusions• We have determined a number of very fundamental

physics questions to answer, like ….– What determines mass?– What is the dark matter?– Are there new symmetries in nature?– What explains the baryon asymmetry?– and others discussed by Gukov

• We are developing the tools to answer these questions and discover new ones– Neutrino Physics– Large Hadron Collider– International Linear Collider

• The next era of particle physics will be very exciting

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Bacher’s Legacy

Identify the most fundamental physics questions and develop (or use the tools) needed to address those questions

Those principles have guided the Caltech nuclear and particle physics efforts for several decades and will continue into the future.