ANTIMATTER
Michael Dine
April, 2006
Prediction of Antimatter
•1931 Dirac, English theoretical physicist, realizes relativity +
quantum mechanics means antiparticle of electron exists. Has
same mass as the electron, but the opposite charge. Called the
``positron”.
matter-antimatter annihilation
p- + p +
g+g
neutrino decoupling
e- + e+
n+n
Discovery of Antimatter
•1933 Positron discovered in cosmic rays
(radiation from space) by Anderson.
Accelerators
Accelerators: Like electron microscopes. Quantum
mechanics: more energy
greater resolving
power. Since the 1940’s, take particles like electrons
and protons to very high energy. If enough energy,
by E=mc2, can produce other particles. Lots of
particles discovered. The largest accelerators today:
•SLAC (e-, e+)
•Fermilab (p-,p+)
•CERN LHC (under construction p- p+)
Aerial View of SLAC
Fermilab – outside Chicago. E= 1000 mp c2
E= 10,000 mp c2
Over 60 years, accelerators have
discovered many types of particles
and antiparticles. One of the first
interesting discoveries:
the antiproton. (Berkeley, 1953)
OWEN CHAMBERLAIN (father of Pia
Chamberlain; passed away earlier
this year; memorial in Berkeley
today)
Nobel Laureate in Physics, 1959
Guggenheim Fellowship, 1957
Professor Emeritus of Physics
UNIVERSITY OF CALIFORNIA,
Berkeley, Fellow of the American
Physical Society, National Academy
of Sciences
Particle physicists have discovered the laws of nature
which operate on scales of atoms, atomic nuclei, and
much smaller (1000 times smaller than the nucleus).
Highlights:
• Quarks (discovered at SLAC, 1969)
• Gluons – hold quarks together in protons and neutrons.
Responsible for the nuclear forces.
• Neutrinos – three kinds. Interact extremely weakly
through matter (pass through huge amounts without
stopping).
• Heavier particles like electrons (“leptons”-muon,tau)
• W’s, Z’s: ``Cosmic Alchemists”
PDG Wall Chart
3 Nobel Prizes in Physics
1976 - Burton Richter
“Charm” or the 4th Quark
1995 - Martin Perl
Tau Lepton
1990 - Richard Taylor
Quarks Structure Inside
Protons and Neutrons
THE BIG BANG
• We know that the universe is expanding today.
• It was much smaller – things were much closer
together – in the distant past. 15 billion years
ago – everything essentially on top of each
other.
• How do we know: 100,000 years after the big,
radiation – the Cosmic Background Radiation.
Discovered by accident.
Artist’s Rendering of COBE
COBE measured the temperature of the universe:
More detailed study of the
CMBR:
From satellites and earth based (balloon)
experiments. Most recently the WMAP
satellite.
Detailed information about the
universe:
Latest from WMAP (March 2006)
COMPOSITION OF THE
UNIVERSE
If 5% of the Universe is Baryons, What is the
Rest?
From studies of CMBR, of distant Supernova
explosions, and from Hubble and GroundBased observations we know:
• 5% Baryons (protons, neutrons)
• 35% Dark Matter (zero pressure)
• 65% Dark Energy (negative pressure)
Sakharov’s Puzzle
When the universe was very hot (1012 oK and
hotter) there was so much energy that
photons colliding produced protons and
antiprotons, neutrons and antineutrons.
Almost exactly as much matter as
antimatter. The tiny bit of excess matter is
what we see today as stars, planets,
people…
Sakharov explained how one could
understand this small difference. Crucial is
that nature is not exactly symmetric
between matter and antimatter. Not many
situations where one can study this small
difference – one is here at SLAC (BaBar).
Need also to understand how this difference
is processed in the Big Bang.
Inner part of Babar – Silicon
Vertex Detector (UCSC)
http://www.space.com/scienceast
ronomy/antimatter_040831.html
http://unisci.com/stories/20011/0
219014.htm
http://scipp.ucsc.edu/~dine/
http://www.slac.stanford.edu/BF
ROOT/
What comes next?
Many questions still to answer. Many speculations on
the answers (supersymmetry, string theory).
2007: A new accelerator at CERN (Geneva)
Experiments looking for the dark matter
Farther into the future: the International Linear Collider
http://www4.nationalacademies.org/ne
ws.nsf/isbn/0309101948?OpenDocume
nt
The Large Hadron Collider - LHC
CMS
ATLAS
The Large Hadron Collider: _
proton-proton collider (no p)
⇨2 separate beampipes
first collisions in 2007
high energy: s = 14 TeV
40 Mio. collisions per second
4 experiments:
ATLAS, CMS, ALICE, LHC-B
10 fb-1 per year
Courtesy A. Quadt
LHC dipoles
LHC quadrupoles
The ATLAS & CMS Experiment
weight
height
length
magnet (solenoid)
7 000 t
22 m
42 m
2 Tesla
weight
height
length
magnet (solenoid)
12 500 t
15 m
22 m
4 Tesla
Precise tracking and vertexing
silicon pixel and strip detectors & transition radiation det.
2 & 4 T solenoid and toroid magnets (air core or iron core)
EM & Had Calorimeters and muon systems
Fast DAQ/trigger
resolutions:
EM: σE/E = 0.5 - 10% / sqrt(E)
~ 1 600 physicists each
HAD: σE/E = 50 – 70 % / sqrt(E)
Courtesy A. Quadt
The ATLAS and CMS Experiment
The Stanford Synchrotron Radiation Laboratory
• SPEAR is the small storage ring where the charm
quark was discovered.
• Accelerated electrons give off light including xrays
• During HEP runs, this light was used parasitically
to study materials.
• So many uses for this intense x-ray source were
found that now all of SPEAR is devoted to
research using synchrotron light.
• It is so useful that about 50 dedicated light sources
have been built around the world.
Protein Crystallography with
Structure of RNA
Synchrotron
Light
polymerase II enzyme
Measured with X-ray
diffraction
This enzyme reads the DNA
to make RNA
Molecular weight of
500,000
Resolution of 2.8
Angstroms
The protein shape
determines how it works.
Setting up to mass produce
such measurements on
thousands of proteins.
Using Synchrotron Light
• X-ray spectra used to
understand the magnetic
layers on a disk drive.
• Makes use of the
polarization, high
brightness, and fine
wavelength selection
from SSRL
• Phys. Rev. Lett. 87,
247201 (December 10,
2001)
Spin-offs
• Medical accelerators
– 1 in 7 of you will owe your life to cancer treatment from a medical
accelerator
– There are 5000 such accelerators in the US.
• Synchrotron radiation
– There are about 50 facilities around the world
– First was here at SLAC (still upgraded and used)
• WWW
– Created at CERN in Geneva, our sister lab
– SLAC put up the first American web site
– First killer app was SLAC’s online HEP publications database.
• Polarized helium or xenon for lung imaging