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 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
5-Nov-05 Bacher Symposium 5
But, not quite high enough energy ….
DiscoveryOf
CharmParticles
and
3.1 GeV
Burt RichterNobel Prize
SPEAR at SLAC
5-Nov-05 Bacher Symposium 6
The rich history for e+e- continued as higher energies were achieved …
DESY Petra Collider
5-Nov-05 Bacher Symposium 8
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
5-Nov-05 Bacher Symposium 10
Neutrinos observed from the sun !
Davis and Bahcall
Koshiba
Superkamiokande
5-Nov-05 Bacher Symposium 11
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
5-Nov-05 Bacher Symposium 12
Puzzle resolved … neutrinos oscillate
SNO (Canada) used D20 to detect other neutrino types
KamLAND used terrestrialneutrinos from reactors,
observes oscillations (McKeown)
5-Nov-05 Bacher Symposium 13
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
5-Nov-05 Bacher Symposium 14
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?
5-Nov-05 Bacher Symposium 15
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
5-Nov-05 Bacher Symposium 18
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
5-Nov-05 Bacher Symposium 19
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 !
5-Nov-05 Bacher Symposium 20
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
5-Nov-05 Bacher Symposium 21
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
?
5-Nov-05 Bacher Symposium 22
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
5-Nov-05 Bacher Symposium 23
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
5-Nov-05 Bacher Symposium 24
Superconducting RF Cavities
High Gradient Accelerator35 MV/meter -- 40 km linear collider
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
5-Nov-05 Bacher Symposium 27
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