ANTIMATTER

A beam of particles is a very useful tool.

Trans Atlantic Science School

2016

Antimatter! 1

Antimatter

History! 3

Theory and properties! 4

Producing antimatter! 6

Antimatter research! 7

Fermilab’s programs which use antimatter! 8

Use! 8

Ideas using antimatter to treat cancer! 9

Unsolved mysteries! 9

Antimatter ! 2

ANTIMATTER

HistoryThe first theories of antimatter were presented in the 1880‘s. Arthur Schuster was the

first who used the term antimatter and antiatoms. Paul Dirac presented the modern

theory of antimatter in 1928. It was the first theory which predicted the existence of

antimatter. He explained it with a theory called Dirac Sea. Dirac supposed that there

could be particles which have negative energy. These particles could construct antimatter.

Afterwards better theories has been explained and Dirac Sea has been forgotten.

Carl Anderson was the first person who found an antiparticle. He studied the masses of

different particles in 1932. He used a mist chamber and magnetic fields. Every time a

particle went through the chamber it left small mark of its trajectory. Anderson noticed

that there should be particle which has the same mass as an electron but an opposite

electric charge. He called it a positron.! ! ! ! ! ! !

Over twenty years later in 1955, Emilio Serge and Owen

Chanberlain found the next piece of antimatter. Their team

discovered antiprotons. An antiproton, like a positron, has

an opposite charge but the same mass as a massive particle.

A year later in 1956, an antineutron was found in the same

place. Antineutrons have no charge, but their properties

were opposite in comparison with a neutron. This is caused

by quarks inside the neutron.

After the 1960’s new antimatter particles were found. New theories have been shown and

some of these have been proved. In the year 1965, they were able to construct

antideuteron atoms at CERN. They succesfully combined antineutrons and antiprotons.

http://timeline.web.cern.ch/timelines/The-story-of-antimatter

www.helsinki.fi › ~enqvist › artikkeli.dir

https://en.wikipedia.org/wiki/Antimatter

Antimatter ! 3

Theory and propertiesEvery particle has an antiparticle, or the particle is its own antiparticle. Antimatter

particles are frequently written with a bar on top. Antimatter particles have the same

mass as their matter particles. Annihilation between matter and antimatter particles

produces energy equal to E=mc2, which means that if one gram of matter and one gram of

antimatter annihilate, the produced energy is equal to 1.779751 * 10^15 joules. It is the

same amount of energy as 50 kilotons of TNT. Annihilation between antimatter and

matter particles produces gamma rays (high energy photons). In each annihilation the

momentum needs to be conserved which means that it needs to produce two photons.

Antiparticles are involved in many matter interactions. For example radioactive B+-decay

produces positrons. Pions (π+) decay to antimuons and muon neutrinos.   The quantum

properties of antimatter particles are opposite to those of matter particles. For example,

charge, lepton, baryon and spin quantum numbers are opposite. Such properties are

involved in lepton and baryon number conservations in particle physics.

Antimatter ! 4

Baryon numbers (within the brackets): anti-u (-⅓) + anti-u(-⅓) + anti-d(-⅓) -> anti-uud (-1)

= anti-proton -> (-⅓)+(-⅓)+(-⅓)=-1 -> 0=0

Lepton numbers:

Antimatter is produced in so called pair production. Pair production is a mechanism

where neutral boson (example Z boson or photon) decay to particle-antiparticle pair. The

minimum energy that pair production needs for the original particle is at least the

rest-mass energy of the production particles (in electron´s and positron´s pair production

the minimum of energy needed is equal to 1.022 MeV). Pair production decays need to

conserve all particle properties, but it also needs to conserve momentum. That means

that pair production can`t happen in empty space and the original particles need, for

example, atoms to interact with.

Antimatter atoms have positively charged positrons orbiting negatively charged nucleus,

whereas matter atoms have negatively charged electrons orbiting positively charged

nucleus. Antimatter nucleus negative charge comes from antiproton´s negative charge

(matter´s positive charge comes from protons´ positive charge). Antiproton´s negative

charge is product of it’s up and down quarks´ opposite elementary charge to protons

(proton is made of two up-quarks (charge +⅔) and one down quark (charge -⅓)). Anti

up-quark has -⅔ and anti down-quark has +⅓.

University Physics: Young & Freedman

Antimatter ! 5

Producing antimatterAntimatter is commonly produced by particle accelerators. Accelerators use acceleration

cavities which are powered with electromagnetic waves to speed up protons. First protons

are accelerated to collide with the metal. Some of the energy released in the collide

transforms into matter (protons) and antimatter (antiprotons). Positrons are produced in

pair production, for example irradiation matter by gamma-rays. Positrons are also

produced naturally in β+ decay. Producing antiatoms (antihydrogen and antihelium)

positrons and antiprotons have to put together. To store antimatter devices called “traps”

which keeps antimatter away from ordinary matter. Usually traps use electric and

macnetic forces which keep antimatter in the center whitout touching walls. Storing

atoms with neutral charges is much more complicated. Neutal antiatoms must be stored

only with magnetic trap.

Antimatter ! 6

Antimatter is produced also in nature: β+ decay and pair production produces positrons.

Antimatter, antiprotons and positrons, enters the athmosphere in cosmic rays, but less

than 1% of the particles in cosmic rays are antimatter. Research by the American

Astronomical Society discovered antiprotons originating above thunderstorm clouds.

Them are produced in gamma-ray flashes (strong electric fields in the clouds accelerate

electrons which creates gamma-rays).

https://en.wikipedia.org/wiki/Antimatter

http://socrates.berkeley.edu/~fajans/ALPHA_Spanish/EN_produccion%20new.htm

Antimatter researchExperiments are using mainly antiprotons to study the properties of antimatter. Produced

antiprotons have high energy level and almost speed of light so them have to slow down

so that physicists can research their properties. The challenge is to create antiatoms and

keep them away from ordinary matter for long enough to study them.

At CERN antiprotons are made in the Antiproton Decelerator (AD) which provides low

energy antiprotons for antimatter studies. First a beam of protons is fired into a block of

metal. The energy from collision can create a new proton-antiproton pair. About one

proton-antiproton pair is created in every million collisions. AD makes low energy

antiproton beam. Focusing magnets keep antiprotons on the same track and strong

electric fields slow them down. Antiprotons go out of AD when they travel 10% of speed

of light. Then antiprotons go to studying experiments, for example ACE, AEGIS and

ALPHA. ACE studies the biological effects of antiprotons. AEGIS uses antiprotons to

measure Earth’s gravitational acceleration. ALPHA makes, captures and studies

antihydrogen atoms and compares with hydrogen atoms. In 2011 it had succeeded trapped

antimatter atoms for over 16 minutes.

http://home.cern/about/accelerators/antiproton-decelerator

http://home.cern/topics/antimatter

http://home.cern/about/experiments/alpha

http://home.cern/about/experiments/aegis

http://home.cern/about/experiments/ace

http://press.web.cern.ch/press-releases/2010/12/cern-experiment-makes-progress-towards-antihydrogen-beams

Antimatter ! 7

Fermilab: Fermilab makes antiprotons by collide protons against a nickel. Fermilab used

particle accelerator called Tevatron. Tevatron was the world’s highest-energy particle

accelerator until the year 2009 and the second most powerful particle accelerator before

it shut down on September 29, 2011. It accelerated protons and antiprotons. Accelerator

makes about 20 antiprotons for every 100 million protons they collide with the

target.Then they are collected in the accumulator. The antiprotons are transfered over to

the Recycler ring and then cooled. Antiprotons are cooled so them are easier to study.

http://www.fnal.gov/pub/tevatron/tevatron-accelerator.html

Fermilab’s programs which use antimatterFermilab E-906/SeaQuest

The Fermilab E-906/SeaQuest experiment is designed to measure the quark and

antiquark structure of the nucleon and the modifications to that structure. The primary

focus of this experiment was to measure the asymmetry of down and up antiquarks in the

nucleon sea. The experiment was started in 2010 and collected data for 2 years.

https://en.wikipedia.org/wiki/Fermilab_E-906/SeaQuest

http://www.phy.anl.gov/mep/SeaQuest/

UseNowadays antimatter is used in positron emission tomography (PET). The PET-device

produces a three-dimensional picture of the functional processes in the body. It detects

pair of gamma rays emitted by electron-positron annihilation.

In the future it might be possible to use antimatter particles as an energy source because

in accordance with Einstein’s famous equation of mass-energy equivalence, a small

amount of antimatter mass can be converted into a huge amount of energy. Currently we

have problems producing and storing antimatter and it’s also difficult to utilize the

released energy. Matter-antimatter annihilation could be used as a fuel for example

interplanetary travel if scientist solve the problems some day.

Antimatter ! 8

Ideas using antimatter to treat cancerAntimatter is used to treat cancer. Positrons are beamed through a tissue in such velocity

that they do not annihilate until they encounter with cancer cells. Formed gamma rays

damage the cancer tissue.

There has also been theories of antimatter weapons. Annihilation could be used in a

bomb instead of nuclear fission. It would raise a lot the mass-to-energy ratio of the

system because matter-antimatter annihilation releases much greater amount of energy

than nuclear fission. Antimatter could also be used as a powerful trigger mechanism in

nuclear bomb. The method is called antimatter-catalyzed nuclear pulse propulsion.

//http://www.faqs.org/patents/app/20090022257

//http://ffden-2.phys.uaf.edu/213.web.stuff/Scott%20Kircher/fissionfusion.html

//http://www.bibliotecapleyades.net/ciencia/ciencia_antimatterweapon.htm

Unsolved mysteriesTheories wich haven’t been proved

Paul Dirac proposed that every particle of matter should have an antimatter counterpart.

However, we are able to detect only matter particles in the universe. According to the

latest research, antimatter particles annihilated soon after the big bang. The interesting

question is why there is still matter which forms our universe?

//http://home.cern/about/engineering/storing-antimatter

Scientist have proposed many theories which haven’t yet been confirmed. The most

popular theory tells that there was slight difference between annihilated amounts of

matter and antimatter particles few seconds after the big bang. The another theory says

that all of the antimatter particles haven’t annihilated. It would mean that somewhere

there is an isolated part of the universe which is consisted of antimatter.

//https://www.newscientist.com/article/dn16780-antimatter-mysteries-1-where-is-all-the-antimatter/

//https://www.youtube.com/watch?v=qS7ueguKp14

In era after the Big Bang, when strong- and electroweak interactions were converged

(known as Grand Unified Theory-era: GUT-era), there could be asymmetry between

matter and antimatter because baryon numbers didn’t need to conserve. After the

Antimatter ! 9

GUT-era the electroweak interactions should’ve balanced the asymmetry between matter

and antimatter. This being the case, the asymmetry should’ve had happened at a much

later epoch.

It’s known that antimatter have the same kind of mass than antimatter, but how does the

gravity influence between matter and antimatter? If we could have an apple made of

antimatter and drop it here on earth, would the apple go up? At the time world-class

scientist are trying to find funding to a project where they are trying to cool antimatter

molecules near the absolute zero by lasers to research how gravity affects to antimatter.

https://www.newscientist.com/article/dn16204-antimatter-mysteries-3-does-antimatter-fall-up/

http://projectantimatter.strikingly.com

http://antimatter-in-depth.strikingly.com

Nowadays it’s very hard to produce antihydrogen, but some day it might be possible to

create anti-diamonds or anti-deoxyribonucleic acid (DNA)? It’s much easier to control

charged anti-particles because them can be controlled by magnetic fields, but soon as we

are producing antiatoms with no charge, things get complicated because those antiatoms

start to annihilate with matter. It would take many years to develop the technology for

producing complicated anti-atoms. Finding an antistar which produces heavier elements

would be easier to use in a research but might be impossible to find

https://www.newscientist.com/article/dn17018-antimatter-mysteries-can-we-make-an-anti-world/

Antimatter ! 10