What’s the Matter With Antimatter?

Dr. Natalie A. Roe

Lawrence Berkeley National Laboratory

The Prediction of Antimatter

• 1900 - 1920’s: Development of relativity, quantum mechanics

• 1928: Paul Dirac’s relativisitic equation of motion for the electron • Predicted the positron,

antimatter partner of the electron

• Predicted that negative protons must also exist

• Speculated that half the stars may be made of antimatter

1933 Nobel Prize in Physics

The Discovery of Antimatter

• The positron was discovered in 1932 in cosmic rays by Carl Anderson

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

1936 Nobel Prize in Physics

What is a Fundamental Particle?

• Greeks: Earth, Air, Fire, Water

• 1897: Thomson discovers the electron• 1911: Rutherford discovers the nucleus• 1919: Rutherford discovers the proton• 1932: Chadwick discovers the neutron

• 1800’s: Periodic table of the elements

• 1967: Kendall, Friedman and Taylor discover quarks in electron-nucleon scattering experiments at SLAC.

• Quarks

• are fractionally charged• occur in pairs or in triplets,

never singly• are point-like objects (to the

limit of our ability to measure)

Quirks of quarks …• Two types of quarks are needed to

make our world, “up” and “down”• proton = (uud) and neutron = (udd)• protons and neutrons form nuclei• add electrons to form neutral atoms• neutrinos are emitted in nuclear

processes that power the sun• 4 fundamental particles are building

blocks of our world

Charge

Increasing Mass

• 2 additional generations of particles have been discovered• Why 3 generations?• What determines their masses?• What determines their decays?

• Do all particles have antimatter partners?

Discovery of the Anti-proton at Berkeley Lab in 1955

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Surrounding Edward Lofgren (center), head of the Bevatron, are discoverers of the antiproton, (left to right) E.Segre, C.Wiegand, O. Chamberlain and T.Ypsilantis.

E.O. Lawrence, inventor of the cyclotronand founder of Berkeley Lab

1939 Nobel Prize in Physics1959 Nobel Prize in Physics

The Mirror Universe

• All fundamental particles have anti-matter partners

• The neutrinomay be its own anti-particle

• Quark and anti-quarks form bound

states called mesons

• ud K0ds

• B0 bd B0 bd

The “Standard Model” particles

Matter and Energy• Einstein first realized the equivalence of

matter and energy• When matter and antimatter meet, they annihilate into energy

• Energy can also materialize as particle-antiparticle pairs

• This is what happened in the “Big Bang”

e-

e+

e-

e+

Feynman diagram

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Antimatter Production in the Sun• Every second, thermonuclear reactions in the sun convert

600 million tons of hydrogen into 595 million tons of helium, and 5 million tons of mass is converted to energy• p + p => pn (deuterium) + e+ + • pn + p => 3He + • 3He + 3He => 4He + p + p

• Solar flares accelerate particles, producing electron-positron pairs.

• ~ 0.5 kg antimatter produced in large flare!

• Image of flare by RHESSI satellite (PI Bob Lin of UC Berkeley/SSL)

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Gamma Ray emissionfrom Solar flare onJuly 23, 2003

Blue = 0.3 - 0.5 MeVPurple = 0.7 - 1.4 MeVRed = 2.2 MeV

Where is all the Antimatter?• No antimatter within our galactic cluster • Can Universe be a quilt of matter & antimatter

domains?• Gamma ray spectrum in space rules out

antimatter domains smaller than ~1000 Mpc

• No evidence yet for antimatter in primordial cosmic rays

The AMS experiment will search for primordial antimatter from its orbit on the International Space Station

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

   Results 1 - 10 of about 589,000 for antimatter [definition]. (0.10 seconds)  

  Antimatter:Mirror of the UniverseA thorough discussion covering all aspects of antimatter.livefromcern.web.cern.ch/livefromcern/antimatter/ - 13k - Cached - Similar pages

. Sponsored Links

. antimatter Low Prices & Huge Selection antimatter Ebay.com

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

You Like Quantum physics?Gain Extreme Wealth and Success By Manifesting Your Own Reality!ICreateReality.com

Gravity BreakthroughBestseller explains gravity. Solves today's greatest science mysteries!TheFinalTheory.com

If the Law of Attractionhasn't worked for you, I know why. Three things that must come first. www.ProvocativeCommunications.com

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

DarkEnergy:~70% Dark

Matter:~25%

Energy budget of Universe

Antimatter: 0% ~25%

~70%

Symmetries of Matter: C, P and T

C = Charge conjugation: particle antiparticle P = Parity (mirror reflection): x -x

C and P together change matter to antimatter;

T = Time reversal: t -t

The product CPT: always invariant!!!

e-

e+

CP Mirror

e-

e+

e-

e+

1957 Discovery of Parity Violation

The Universe knows its right hand from its left!

C.S. WU

Co60

B field

e-

e

n -> p e-

Beta Decay of Co60

Another way to look at CP Violation

Bob Cahn

Left-handed particle => Right-handed anti-particle

An Unexpected Discovery In 1964

Cronin and Fitch discovered CP violation in thedecay of the long-lived, CP-odd neutral K meson into a CP-even final state: Br(KL ->

There is a difference between matter and antimatter!

“We are hopeful… that at some epoch, perhaps distant, this cryptic message from nature will be deciphered.” J. Cronin

1980 NOBEL PRIZE J.CroninV. Fitch

CP Violation => T Violationunless CPT is also violated!

Antiproton Decelerator at CERN

ATHENA experimentAnti-hydrogen annihilation

near walls of trap

Prototype for a next generation experiment to trap anti-hydrogen and characterize with laser spectorscopy. J. Fajans, J. Wurtele et al

Discovery of CPT violation would be revolutionary!

Alpha Test Trap and Superconducting Magnet Prototype built at LBNL

Sakharov’s Recipe for BAU (1967)(Baryon Asymmetry of the Universe)

Necessary ingredients are:• Baryon number violation• Thermal non-equilibrium• C and CP violation

• Do we understand the cause of CP violation in particle interactions?

• Can we calculate the BAU from first principles?

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this p icture.

1975 Nobel Peace Prize

(nB - nB )/ n= 6.1 x 10-10

All of these ingredients were present in the early Universe!

An Astounding Connection

• In 1973, M. Kobayashi and T. Maskawa predicted: CP violation third generation of quarks!

• Subsequent discoveries confirmed the prediction:

•b quark was discovered in 1977 at Fermilab by Lederman et al

• t quark was discovered in 1994 at Fermilab by CDF and D0

• The three-generation Standard Model naturally includes CP violation in certain particle decays.

ud

cs

tb

quark doublets

ee

lepton doublets

Standard Model Particles

An Asymmetric B Factory to Study CP Violation

• CP violation in K0 ( sd) meson decays was exhaustively studied for over three decades

•the effects are very small, and hard to interpret theoretically

• In B0 ( bd) meson decays, the Kobayishi- Maskawa theory predicts large CP violation effects

•besides being large, the effects are theoretically clean

• But - the decay rates are small => need to produce millions of B mesons in a B “factory”

• To observe the CP asymmetry between B and anti-B mesons, a special type of e+e- collider is required with unequal beam energies - the Asymmetric B Factory

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

1999: Pier Oddone and Jonathan Dorfan in the PEP-II tunnel

PEP-II

Stanford Linear Accelerator Center,Stanford, California

Approved as a PresidentialInitiative in 1993; completedin 1999. Reached full designluminosity in 2000.

Japanese B Factory has also been built with similar design.

The BaBar Collaboration: ~600 physicists from 73 institutions and 9 countries

The BaBar Detector

How the BaBar Detector Works

CP violation occurs in the interference between mixing and decay to a CP eigenstate, eg B0

Measuring CP Violation with B0s

Not equal –

CP Violation!

B0(t) fCP

B0

B0

B0(t) fCP

B0

B0

B0B0 Mixing

• Matter-antimatter oscillations occur in neutral K0 and B0 mesons

• Mixing adds CP violating couplings, with time dependence

• Observation of the time dependence requires the use of asymmetric energy beams • this boosts the B mesons so they travel a measurable

distance before decaying• measuring the B decay vertices establishes when the B

decayed

B0 B0

b

b d

d t

t

W W

the mixing “box” diagram

first - third generationcoupling

The Asymmetric B Factory Concept

decay of B “tag” CP eigenstate

e+ e-S)

9 GeV e-

t z

3 GeV e+

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

• B0 J/Ks is the best decay mode to measure the CP violating angle , the phase due to the mixing diagram

• B0 J/Ks also has a relatively large branching ratio (1 per million) and is “easy” to reconstruct

Golden Mode for CP Violation in B decay

b

d

ccsd

W+

Ks

J/

Recipe for Measuring CP Violation in B Meson Decays

• Produce many B0 B0 pairs (hundreds of millions)• Reconstruct one B in a special decay called a CP eigenstate• “Tag” the other B0 to make the matter/antimatter distinction• Determine the time between the two B0 decays, t• Compare t distributions for

B0 and B0 tagged events; the difference measures CP violation, the difference between matter and antimatter

B tagged

B tagged

t (ps)

270 Million BB pairs produced since 1999 and recorded by the BaBar detector

Year

How to “tag” a B or anti-B meson: The DIRC Detector

Angle of Cherenkov light is related to particle velocity

– Transmitted by internal reflection

– Detected by~10,000 PMTs

c

Particle

Quartz bar

Cherenkov light

Active Detector Surface

KDDD 00* ,

B0

e+

D 0

K+

--

B0 D* e

How to measure the decay times:The Silicon Vertex Tracker (SVT)

Uses five layers of silicon microstrip detectors to measure B decay verticesto better than 0.1 mm and determine the time between the two B meson decays.

Tracking Charged Particles in the SVT

Latest results from BaBar on difference of matter and antimatter:

Sin2

What does this result mean?

sin2=0.72±0.04

• Maximum asymmetry => sin21• Zero asymmetry => sin20• Much larger asymmetry than in K0 decays

(72% vs 0.2%); combined experimental plus theoretical error is small

• The result is consistent with the prediction of the three-generation Standard Model

• But: our best calculations of early Universe do not produce enough excess matter - off by 10 orders of magnitude!

What is the Matter with Antimatter?• How can a parameter between 0 and 1 provide the

missing 10 orders of magnitude? • It can’t• New particles can provide the required CP violation• The effects of new particles may be observable in B

decays…

sin 2in a different mode

• sin2measured in final states with charm agrees with the Standard Model predictions

• sin2can also be measured in other “penguin” decays and should agree within a few percent

• New physics could enter in loops!

b

d

ccsd

W+

Ks

J/

tree diagram penguin diagram

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

World average for sin2 in “penguins” compared to J/Ks

… hint of new physics, or a statistical fluctuation?

Future Prospects for BaBar…

• The BaBar experiment has published ~ 150 papers so far in refereed journals on a wide variety of topics

• Expect to collect ~4x more data over next 3-4 years => statistical errors will decrease by x2

• In a race with the Japanese B Factory • behind right now in total luminosity• advantage in the ability to confirm any

unexpected results• The Large Hadron Collider at CERN will turn on in

2007, data taking by 2008 • could directly produce new particles

Summary

• CP violation is required in any theory starting from the Big Bang to explain the dominance of matter over antimatter

• Antimatter exists and can be created at accelerators; but there is very little antimatter naturally occurring in our Universe

• CP symmetry between matter and antimatter is violated at the quark level, as measured by BaBar - but not enough !

• More detailed measurements may give clues to new physics beyond the Standard Model

• Antimatter engines on Starship Enterprise were powered by p + p annihilation!

The Anti-Hydrogen Economy?

• Distinguish between energy source and method to store and transport energy -

Creating, storing antiprotons requires a lot of energy, and trapping them is also very inefficient

All the antiprotons created in one year at Fermilab would only power a 100 watt bulb for 30 minutes, even with 100% trapping and conversion efficiency!

• Cost: $62.5 trillion per gram!

Penning Trap

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Penn State UnivPenning TrapQuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this picture.

What’s the Matter with Antimatter?

• Our present view of matter - the “Standard Model” of particle physics

• The amazing prediction and discovery of antimatter

• Is antimatter useful, Dr. Spock?• Colliding matter and antimatter• What happened to all the antimatter ?

- the search for CP Violation• Why does it matter?

Latest result:Sin2