Overview of CERN & the physics raison d’être

The search for elementary particles

explanation of the universe

Historical perspective

Particle physics & forces

Slide show – accelerator, experiments, technology

http://hepwww.rl.ac.uk/ppdstaff/Tyndel/NZ2006/CERNs.ppt

Sign in Geneva airport

• CERN is:– The European Organization for Nuclear Research

– The world's largest particle physics centre (now)

– It is on the Franco-Swiss border near Geneva.

Goal of CERN is particle physics research (which links to the physics of the universe)

• CERN is a laboratory with 2500 staff, 6500 users & 500 associates/fellows who study the building blocks of matter and the forces that hold them together.

• CERN exists primarily to provide them with the necessary tools.

• These are accelerators, which accelerate particles to almost the speed of light and detectors to make the particles visible.

• The budget is 1.3Bn SFr per year– [Figures from 2005]

An accelerator:

1) produces particles

2) accelerates them using an electric field

3) constrains them using a magnetic field

Particle detectors – devices which can “see” particles and measure their trajectories and energy

• Why accelerate particles?

• Accelerate means giving particles energy

1. This energy allows us to look « inside » matter for substructure (Heisenberg:

p.x ~ h)

2. Also the energy can create new particles (Einstein E = mc2 )

Founded in 1954, the laboratory was one of Europe's first joint ventures and includes now 20 Member States.

Historical diversion• William Thomson, Lord Kelvin (1824 – 1907)

Belfast Glasgow , Cambridge , Glasgow

• Thermodynamics, Electricity, Atomic theory, Age of the earth…..

• "Scientific wealth tends to accumulate according to the law of compound interest. Every addition to knowledge of the properties of matter supplies [the physical scientist] with new instrumental means for discovering and interpreting phenomena of nature, which in their turn afford foundations of fresh generalisations, bringing gains of permanent value into the great storehouse of [natural] philosophy." ["Presidential address to British Association", 1871]

• "There is nothing new to be discovered in physics now, All that remains is more and more precise measurement.”

… but Kelvin was not the first or the last to be wrong about knowing nearly everything

Résumé particle physics BC (before CERN)

• Antiquity : Four elements. Unsuccessful attempt at an atomistic theory during the 5th century BC (Democritus).

• 18th century : Lavoisier and Dalton verify experimentally the validity of the atomic structure.

• 1868 : Mendeleev proposes his chart of elements, containing the 63 atoms known at the time. The “empty cases” he left were soon filed. By 1896, 77 atoms have been discovered, and are considered elementary.

• 1897 : Discovery of the first subatomic particle by J.J Thompson : the electron.

• 1911 : Rutherford discovers the nucleus. Transmutation reactions showed that the hydrogen nucleus played a specific role (4

2He + 147N --> 18

9F --> 17

8O + 11p) . Rutherford named it proton (protos =

first)

Historical diversion

• Baron Ernest Rutherford (1871 – 1937)

New Zealand Cambridge Canada Cambridge

• Chemistry, Structure & splitting of atom

• "All science is either physics or stamp collecting."

• 1932 : Chadwick discovers the neutron, which is not stable when isolated, and decays as follows : n p + e- (+ ¯νe) . The proton, electron and neutron account for all the atoms of all the elements in the Universe.

This was the “simplest” elementary particle set ever described. A small number of particles, a small number of interactions or forces.

• LEPTON (leptos = light) : e- and BARYONS (baryos =

heavy) : p , n

• Gravitational, Electromagnetic & nuclear forces

• And finally we arrive at 1949…– The 2nd world war is over– Physicists had a visible role in ending the war– Europe is considered a “basket case”

• 1949: Louis de Broglie proposes the creation of a European science laboratory during the European Cultural Conference at Lausanne.

• 1950: Rabi puts forward a resolution, which is unanimously adopted, authorising the Director General of UNESCO, "to assist and encourage the formation and organization of regional centres and laboratories in order to increase and make more fruitful the international collaboration of scientists ...".

• 1952: After two UNESCO Conferences, a site near Geneva is selected for the planned laboratory.

• 1954: CERN formally created on 29th September.

CERN beginnings

• 1957: The 600 MeV Synchro-Cyclotron begins operation. One of the first experimental achievements is the long-awaited observation of the decay of a pion directly into an electron and a neutrino.

• 1959: The worlds highest energy accelerator (28GeV PS) and the neutrino beam completed.

• 1963: First bubble chamber pictures of neutrino interactions

• 1968: Electronic detectors (wire chambers) invented A later bubble chamber - BEBC

• 1973: First results from “ISR colliding beams” show that the proton “size” increases with energy.

• 1973: Neutrino neutral currents discovered. Forces unified.

• 1976: A new super accelerator built (500GeV SPS)

• 1981: Stochastic cooling invented allowing conversion of SPS into a collider .

• 1983: Discovery of the “carriers of weak force” (W, Z).

• 1989: LEP, a machine built to investigate the W and Z starts and proves that there are 3 families of quarks

• 1989 : WWW ‘hypertext’ (the world wide web) invented @ CERN to ease communication between computers

• 1989-2000: Results from LEP establish the “Standard model” as the theory of particle physics.

• 1996: Antimatter created at CERN

• 1994: Start of construction of worlds highest energy machine (14,000GeV LHC) – expected in 2007

• So many new particles were being discovered so that in 1955, Willis Lamb started his Nobel Prize speech by saying that “maybe physicists discovering a new particle ought to be fined $10,000”

• Gell Mann saw the pattern in 1961. Just as Mendeleev had done for atoms, a century before, he deduced that there was a substructure with 2 types of quarks held together by gluons.

• And the rest of the quarks were found:– 1974 charm quark– 1977 bottom quark– 1975 tau lepton– 1995 top quark

– 1977 gluon jets

• And in 1998- The neutrino was discoveredto have small mass

…and to complete the global picture

In 50 years, there has been a revolution in understanding…

• Are we at the end of the road?– [Remember Kelvin]

• Not likely– Hope to see the Higgs (see next slide) at LHC

– Suspect that there is a complete shadow world of particles [SUSY]

– Have a dream that all forces including gravity will be unified

• What is Higgs for?– It is a field that fills the universe and gives particles mass

THE “CELEBRITY AT PARTY” MODEL (quarks or leptons)

THE “rumour” model (Higgs particle)

Particle Mass determined by strength of interaction with higgs field

• Stars and Planets only account for a small

percentage of the universe !

27KM tunnel 100m below the surfaceWorld’s Largest cryogenic system ((1.8 K, suprafluid helium)

CERN Technologies

Dipoles for the LHC arrive from industry

Magnet – Cryostat Assembly

Magnet installation

ATLAS Cavern

Concorde(15 Km)

Balloon(30 Km)

CD stack with1 year LHC data!(~ 20 Km)

Mt. Blanc(4.8 Km)

Data in Large Quantities

What is the Grid?

• The World Wide Web provides seamless access to information that is stored in many millions of different geographical locations

• In contrast, the Grid is an emerging infrastructure that provides seamless access to computing power and data storage capacity distributed over the globe.

CMS

Technology Transfer Projects

Silicon detector for a Compton camera in nuclear medical imaging

Thin films by sputtering or evaporation

Medipix: Medical X-ray diagnosis with contrast enhancement and dose reduction

Radio-isotope production for medical applications

Radiography of a bat, recorded with a GEM detector

CERN as Educator

Bringing Nations Together

“…the promotion of contacts between, and

the interchange of, scientists…”

CERN…

• Seeking answers to questions about the Universe

• Advancing the frontiers of technology• Training the scientists of tomorrow• Bringing nations together through science

• Backup1) Einstein

2) Cosmology slides

• Another motivation drove Rabi. He considered CERN a peaceful compensation for building the nuclear bomb. This was revealed when I invited him to speak at CERN's 30-year anniversary celebration in 1984. Here are excerpts from his comments:

• CERN was founded less than 10 years after the bomb was made. I feel that the existence of the bomb and its success had a large part in making CERN possible. . . . I am not at all surprised at the great achievements of CERN. I expected that. I was sure that Europe, which was the cradle of science, once brought back into the path, would achieve some very great things. . . . I mentioned Los Alamos and the atomic bomb, which is an expression of the power of [the] personalities [involved]. They are here now before you, and it is important to keep them occupied fulfilling the ideals of science. . . .

• I hope that the scientists at CERN will remember that they have other duties than exploring further into particle physics. They represent the combination of centuries and centuries of investigation and study and scholarship to show the power of human spirit. So I appeal to them not to consider themselves as technicians . . . but . . . as guardians of this flame of European unity so that Europe can help preserve the peace of the world.

• By bringing together scientists from Europe and the rest of the world, CERN has lived up to this objective better than its founding fathers expected.

• Herwig Schopper

• Albert Einstein (1879 – 1955)

Germany Switzerland Germany USA

• Photoelectric effect (wave/particle), Relativity, E = mc² , Cosmology & gravitation

• “I never think of the future - it comes soon enough.” • • "If we knew what it was we were doing, it would not be called research”

• “Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." --Albert Einstein”

• “Imagination is more important than knowledge...”

Arguably the greatest scientist ever – and his views remain fashionable

Gravity at large distances

Einstein

Newton

“UniversalGravitation”

Mass and energyCurve space-time

Gravity at small distances

Collapsing stars produceBlack holes

Observation of a black hole candidate

What is a singularity ?

really small distances Gravity : dominant force at r ~ 10-33 cm

Quantum Gravity ?

Superstrings in 11 dimensions?

Does gravity only act in 3 dimensions?

- Macroscopic : YES ( 1/r2 law)- Microscopic : no information for r < 10 µm

What is a particle ?

• Stars and Planets only account for a small percentage of the universe !

Cosmology – Big Bang•

< 10-43 sec: Planck era

~10-34 sec: inflation

10-32 sec “big bang”

10-10 ... 1 sec particles

380,000 yrs atoms

BB

Before the Big BANG ?•

The primordial vacuum: 1094 GeV/cm3 ?

• Evidence No. 1 - Cosmic Microwave backgroundEvidence No. 2 - Expansion history of universe

COSMIC EXPANSION SPEED INCREASES!

Driven by ‘dark energy’

•

Courtesy: NASA/WMAP

FIT observation with BIG BANG MODEL - 1) Inflation stretches ‘quantum ripples’2) Light element synthesis (matter)3) Dark (=non-baryonic) matter4) Age and shape of universe

Cosmic Microwave background Temperature Distribution on earth (for comparison)

Temperature Distribution In Universe

T/T ~ 0.3

T/T ~ 3·10-5

Courtesy: NASA/WMAP

A non-baryonic dark halo

Milky Way:Mhalo ~ 10 x Mvisible

Microlensing baryonic matternot the solution

A dark non-baryonic halo, ~ 0.3 GeV / cm3

v ~ 220 km / s

Excluded by

MACHO

MACHOdetection