ANTIMATTER

Michael DineApril, 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”.

e- + e+ +

p- + p+ +

matter-antimatter annihilation

neutrino decoupling

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 havediscovered many types of particlesand antiparticles. One of the firstinteresting discoveries:the antiproton. (Berkeley, 1953)

OWEN CHAMBERLAIN (father of Pia Chamberlain; passed away earlier this year; memorial in Berkeley today) Nobel Laureate in Physics, 1959Guggenheim Fellowship, 1957Professor Emeritus of PhysicsUNIVERSITY 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

1976 - 1976 - Burton Richter“Charm” or the 4th Quark

1990 - Richard TaylorQuarks Structure Inside

Protons and Neutrons

1995 - Martin PerlTau Lepton

3 Nobel Prizes in Physics

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 Ground-Based 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/scienceastronomy

/antimatter_040831.html

http://unisci.com/stories/20011/0219014.htm

http://scipp.ucsc.edu/~dine/http://www.slac.stanford.edu

/BFROOT/

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/news.nsf/isbn/0309101948?OpenDocument

The Large Hadron Collider - LHCThe Large Hadron Collider - LHC

LHC dipolesLHC dipoles LHC quadrupolesLHC quadrupoles

ATLASATLAS

CMSCMS

The The LLarge arge HHadron adron CCollider:ollider: proton-proton collider (no p)proton-proton collider (no p) ⇨⇨2 separate beampipes2 separate beampipes first collisions in 2007first collisions in 2007 high energy: high energy: s = 14 TeVs = 14 TeV 40 Mio. collisions per second40 Mio. collisions per second 4 experiments:4 experiments: ATLAS, CMS, ALICE, LHC-BATLAS, CMS, ALICE, LHC-B 10 fb10 fb-1-1 per year per year

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Courtesy A. Quadt

Precise tracking and vertexing Precise tracking and vertexing silicon pixel and strip detectors & transition radiation det.silicon pixel and strip detectors & transition radiation det. 2 & 4 T solenoid and toroid magnets (air core or iron core)2 & 4 T solenoid and toroid magnets (air core or iron core) EM & Had Calorimeters and muon systemsEM & Had Calorimeters and muon systems Fast DAQ/triggerFast DAQ/trigger ~~ 1 600 physicists each 1 600 physicists each

resolutions:resolutions:EM: EM: σσEE/E = 0.5 - 10% / sqrt(E)/E = 0.5 - 10% / sqrt(E)HAD: HAD: σσEE/E = 50 – 70 % / sqrt(E)/E = 50 – 70 % / sqrt(E)

The ATLAS & CMS ExperimentThe ATLAS & CMS Experiment

weightweightheightheightlengthlengthmagnet magnet (solenoid)(solenoid)

7 000 t7 000 t22 m22 m42 m42 m

2 Tesla2 Tesla

weightweightheightheightlengthlengthmagnet magnet (solenoid)(solenoid)

12 500 t12 500 t15 m15 m22 m22 m

4 Tesla4 Tesla

Courtesy A. Quadt

The ATLAS and CMS ExperimentThe 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 x-rays

• 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 Synchrotron LightStructure of RNA

polymerase II enzymeMeasured with X-ray diffractionThis enzyme reads the DNA to make RNAMolecular weight of 500,000Resolution of 2.8 AngstromsThe 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