A. Bay Beijing October 20051 Some High Energy Physics.

A. Bay Beijing October 2005 1

Some High Energy Physics

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Course Summary

Historical/Philosophical introduction AntiparticlesDetectors & acceleratorsStandard Model of Particles (SM)

Connection with CosmologyWhy do we think that the SM is not the final word ?


What it is made of ? How does it work?


Historical/Philosophical introduction • Physical (fundamental) questions:

what is matter made of what is water ?what animates the matter constitutive of an animal, a

tree ? what is the origin of interactions ?

elementary: gravitationcomplex: hate & love

• Cosmological question: when and how the Cosmos was built. There will be an end ?

• Theological question: why the Universe? What are the reasons for life (and death)?

Many, many attempt in the old time to try to answer this questions.If we leave aside the (too difficult) Theological question, trying to answer to the other questions constitute the "quest" for a (scientific) system of Nature.

I will give you a short list of milestones of this quest.(This is the "European' point of vie, sorry !)


Some history

Anaxagoras (500-428 BC)the Sun is a big ball of fire and the Moon is reflecting its light

theory of minute constituents of things emphasis on mechanical processes in the formation of order

many consider him the father of the Atomic model

Empedocles (484-424 BC)four elements (earth, fire, water, air)light: particles emitted by a source, they travel to the eye and then they return to the source !

Democritus (460-370 BC)Universe is an empty space ("void") filled with atoms in fixed numbermilky way are distant stars0ther worlds should exist with life




Some history .2

Aristotle (384-322 BC)Earth is spherical at the middle of the Universe (cannot "fall").

Aristarcs (310-230 BC)Sun, stars are fixed. Earth turns around the Sun. He searches a wayto measure the distance of stars.

Archimedes (287-212 BC)computes the volume of the Aristarc's Universe: 1063 grains of sands

. . .Galileo Galilei (1564-1642)

mathematical attack of the physical problemexperimental foundation of science inertia, relativity of motionhe adopts Copernicus model of solar

system (almost gets to jail !)




Some history .3

Christian Huygens (1650)wave model of light

Isaac Newtonmechanics, gravitation, particle model of light

Thomas Young (1773-1829) , Augustin Fresnel (1788-1827)wave model of light, interference, polarization

En 1847 Annalen der Physik refuses to publish a Helmoltz paper based on the impossibility of perpetual motion to demonstrate the conservation of Energy !

James Clerk Maxwell (1831-1879)electromagnetism






Some history : 4

At this point (~ 1880) a physicist affirmed somethinglike that:

" 1800 physics has almost accomplished the full comprehensionof Nature. A couple of small problems need still someexplanation: the black body radiation and the Michelsonand Morley experiment "

The most famous experiment with "negative outcome"of history of science


Some history .5

W. Konrad Roentgen: in 1895 discovers X rays

J. J. Thomson: in 1897 measures the electron e/m ratio

1900 : beginning of Quantum Theory M. Plank: describes the black body emission

A. Einstein: in 1905 explain the photoelectric effect. Theory of relativity.

1912 observation of cosmic rays1913 atomic model of Bohr. Beta decay observed1921 spin of particles1924 wave model of de Broglie1925 uncertainty principle of Heisenberg1926 Shroedinger equation1928 Dirac equation


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Some history: a few considerations

1) We need to be patient (no "Mac Donald physics"):it took a lot of time to our ancestors to mature the ideas andconcepts we use today.Fundamental concepts like "symmetry", "energy", "atom", ripened for centuries.

2) Some physicists (around 1900) believed that Relativity and QMwere not important for everyday life ("too fast", "too small"). Wrong: the decades around 1900 were enough to make a revolutionwhich has brought us transistors and lasers (90% of the GNP ofan industrial nation).

3) Some (solid state,...) physicist (today) believes that particle physics is not important for everyday life (too fast, too small)...

Stay tuned !


Antiparticles

AntimatterMatter


Genesis of the concept of antiparticles

(iγμ∂μ −m)Ψ =0

Paul A. M. Dirac

E=mc2

Albert Einstein

E=hν

Max Planck

In 1927 P.A.M. Dirac attempts to marry Quantum theory and Relativity


Genesis of the concept of antiparticles

Previous attempt Klein-Gordon equation

had some problems with probabilistic interpretation

Schroedinger equation, non relativistic


The Schroedinger equation

this equation was very successful for the description of atoms(but needs some corrections...)

€

−h2

2m∇ 2 + V(r)

⎡

⎣ ⎢

⎤

⎦ ⎥Ψ(r,t) = ih

∂

∂tΨ(r,t)

p2/2m a potential

TOTAL ENERGY

energy operator


The Schroedinger equation .2

€

1

2m∇ 2Ψ(r,t) + i

∂

∂tΨ(r,t) = 0

ATTENTION: unless otherwise specified we will use the particle physicists "natural units"

h = c = 1

second orderspace derivative

first ordertime derivative

this equation isa "non-relativistic"approximation !

For V= 0 the Schroedinger equation becomes


The Schroedinger equation .3The Schroedinger equation is the non-relativistic approximationof a more general "relativistic theory":

* It does not contain the rest energy E=mc2

* It was known that "relativistic corrections" are needed forthe atomic model of Bohr/Sommerfeld to much experimental results.The electron velocity in the Bohr atom is ~0.01c, hencefrom Th. of relativity it was found that its total energy ona orbit is modified by a factor

where is the "fine structure constant"

€

δE ∝α 2

€

α =1

4πε0

e2

hc≈

1

137

in principle O(10-4) error if one uses the Schroedinger eq. to get the energy of the electron


The Dirac equation

This equation is very successful in the description of many things.It has 2 fundamental consequences:1) incoroprates the existence of a spin of particles like the electron2) predicts the existence of an antiparticle sector


The quest for a quantum relativistic theory brought Dirac to thisvery very simple formula but with many many consequencesfor our life:

this is mc2this is a 4-dimensional derivative:space and time get same treatment


The Dirac equation .2


Here is a "double spinor" (i.e. a 2x2 components vector)which can encode the information of the particle spin.But why there are two spinors ?Dirac was puzzled by the presence of this second degree offreedom. What is its origin ?

classical energy : E = mv2/2 = p2/2mrelativistic: E2 = m2c4 + p2c2

€

E=± m2c4+p2c22 solutions:

€

=

a

b

c

d

⎛

⎝

⎜ ⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟ ⎟


The Dirac equation .3How to deal with a negative energy ??? Dirac introduces the(unlikely) hypothesis of a sea of electrons with E<0.A photon rises one of these particles to a E>0 level, leavinga hole which behaves also like an E>0 particle, withpositive charge. He makes the hypothesis that this is the proton.

E>0

E<0

electron

proton ?


Antiparticles .1

The electron - proton hypothesis does not work:

the 2 particles must have identical mass

Solution to this problem came from Oppenheimer, Stückelberg, Feynman:they replace the E<0 particles with other (anti)particlesof opposite charge.

Nice theory! Now we have just an experimental problem:we are in 1930; where to search for the anti-electron ?


Dirac equation (technical)

gamma matrices contain Pauli matrices

double-spinor

How to get a current from 2 spinors:

Satisfies


Non relativistic limit of the the Dirac eq.

In the non-relativistic limit, the Dirac eq. gives the Pauli eq.

is now a spinor for the particle

Interaction of the charged spin 1/2 particle withB = rot A is

"Dirac" particles have g = 2 => experiments g2


Solutions of Dirac Equationof the form

Oppenheimer, Stückelberg, Feynman


Antiparticles .2

positron electron

Observation of "positrons" at CAL-Tech par C. D. Anderson en 1932.


BEBC detector at CERN

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BEBC au Cern


Antiparticles .4

1932 positron discovered in cosmics (Anderson et al.)1947-1956 Kaon / antiKaon1955 antiproton (Bevatron of Berkeley, Chamberlain et al.)1956 antineutron (idem)1950-1960 neutrino/antineutrino…

Several isotopes are + emitters(Positron Emission Tomography uses O15, le F18…)


Pair creation

Etotal m(e+) + m(e) = 2 (511 keV) ~ 1.2 MeV

Particle and its antiparticle have the same mass.To create a couple e+ e- (or other kind of particle-antiparticle)the minimum of energy needed is

Energy-momentum conservation does not allow

€

→ e+ e−

A pair creation can only happen in the presence of another particle, an atomic nucleus, for instance:



a real gamma

virtual gamma representingthe e.m. field of the nucleus


Pair annihilation, the positronium

€

e+ e− → γ γ

€

e+ e− → γ γ γ

Slow (~eV) positrons interacts with ordinary electrons andcan form a pseudo-atom state called "positronium" Ps,similar to a Hydrogen atom (E levels ~1/2 of H).

In 75% of the cases the 2 spins are parallel: ortho-Ps (3S1)In 25% of the cases they are anti-parallel: para-Ps (1S0)hyperfine splitting : E = 8.4x10-4 eV

This pseudo-atom has a lifetime of: (singlet)~108 s (triplet)~1010 s

(3S1) (1S0)

Etotal m(e+) + m(e) => for the 2 decay E = 511 keV


Positronium

α ~1/137


Is it possible to assemble positrons and antiprotonsto make anti-Hydrogen atoms ?

If yes, next questions will be :

- Is the antiH stable ?

- May we find antistars in the Universe ?


To build an antiH atom we need

...an antiproton … a positron

…. and an assembly line

-

-

eV (atomic) binding energies involved. Particles must be slow


beam of p

accelerator

fast p

p = protons (ionized H)

targetanti-pselector

anti-pdecelerator

experiments

lot of particlesafter the chock

The production of slow antiprotons


Production of slow anti-p at CERN


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protonsaccelerator

production andselection of antiprotons

AD: antiprotons decelerator

experiments


production 2



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production of anti-proton at CERN


AD magnets


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Assembly linewith Penning traps

anti-p trap

positrons trap

assembly region

input ofantiprotons

input ofpositrons


antiH


We have crated antiH

Scientific studies :

• Are the masses of H and antiH identical?• Are the energy levels identical ?• Production and studies of antiH2

• Production and studies of antiD...


Which kind of applications for antiparticles ?

1) Today: medical applications

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2) Ongoing studies forvery high density energy storage,fuel for space travel, …

A little technological interlude...


Positron emission tomography


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PET .2

Injection of a positron emitter withspecific metabolic activity

The drug gets concentrate in target regions of the body(cancers, brain regions in activity,...)

Positon+electron annihilation

gives 2 photonstravelling back to back

particle detectors

gamma

gamma


Isotopes in use for PET


PET allows to study brain activity


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brain reading a texton a screen

brain listening


PET in diagnostics


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PET allows to...

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and tofollow themetabolismof a substance


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create 3Dimages


Total weight 2950 tFirst stage

Weight of propellent 2150 tThrust 3300 t

3300 > 2950 OK: the motor can lift the spacecraft

dM/dt (Burning speed) (duration 160 s) 13 t/secEjection velocity 2.8 cm/s

Le yield of the engine is given by Specific Impulse = Thrust / Burning speed = 253 secand (Thrust/total wght) = 3300/2950 ~1

Space travel with a SATURNE V:


Only antimatter annihilation offers the qualitiesOnly antimatter annihilation offers the qualitiesrequired for a travel to Plutorequired for a travel to Plutoor a pre-interstellar journeyor a pre-interstellar journey

……well, how to build an anti-matter motor? well, how to build an anti-matter motor?

Propulsion type spec. impulse Thrust/wghtchimique 200-400 s 0.1 - 10fission nucléaire 500-3000 s 0.1 - 10fusion nucléaire 10 4 - 10 5 s 10 5 - 10 2

annihilation 10 3 - 10 6 s 10 3 - 1


An antimatter thrusterAn antimatter thruster

1) produce (on Earth) the necessary amount of antiprotons.2) store in a reservoir prototype: HIPAT High Performance Antimatter Trap3) anti-p are put in contact with HLi pellets. The microexplosions produce hot plasma.

plasma is expulsed atvery high velocity


prototype HIPAT Pennsylvania State University

storage of 109

antiprotons


ICAN II


Antimatter projects

V km/s

Mass

g

1 g


production d'antiprotons

Yield in antiproton production increases by afactor of 10 each ~2.5 years

1 g/year

mp = 1.67 10-24 g

1955 2010


Antiparticles reservoires ?

Los Alamos

R&D in production, storage, ...with antipartcles

NASA SBIR Phase II: Construction of a High Efficiency AntiprotonDegrader/Accumulator to Support Advanced Propulsion Research…By the end of the project, we intend to provide a potentially commercial sourceof low energy antiprotons in portable traps to the research community.

USAF BAA Award: storage of 1015 positrons for Earth-to orbit propulsion

A. Bay Beijing October 20051 Some High Energy Physics.

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