Vincent Hedberg - Lund University1 LHC & ATLAS The largest particle physics experiment in the world

Vincent Hedberg - Lund University 1

LHC & ATLASLHC & ATLASThe largest particle physics experiment in the worldThe largest particle physics experiment in the world

http://public.web.cern.ch/public/Content/Chapters/Spotlight/SpotlightCool-en.html


CERN – A CERN – A laboratorylaboratory for the world for the world

There were 12 member statesin the beginning.

CERN was founded in 1954


The 20 member countriesThe 20 member countries

OBSERVERS:•UNESCO•EU•Israel•Turkey

SPECIAL OBSERVERS(for the LHC):

•USA•Japan•Russia•India

Vincent Hedberg - Lund University 4Vincent Hedberg - Lund University 4

CERN in numbersCERN in numbers The CERN budget is about 1 billion

AUD.

Half of the budget is used to pay the salaries for the 2500 employees.

The cost of the LHC accelerator has been about 5 billion AUD.

CERN is responsible for the accelerators.

The 560 universities and institutes that do research at CERN are responsible for the experiments.

In total, 9000 physicists from all over the world are doing research at CERN.


Particle physicsParticle physics The study of the fundamental

building blocks of nature and their interactions.

Small = High Energy

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The building blocksThe building blocks

~1 m ~10-10 m ~10-14 m ~10-18 m

We now know that the smallest constituents of matter are three generations of quarks and leptons.


GRAVITYGRAVITY

Force carrier: Force carrier: The GravitonThe Graviton

Make things fall to the Make things fall to the ground.ground.Make planets go around the Make planets go around the sun.sun.

THE ELECTROMAGNETIC FORCETHE ELECTROMAGNETIC FORCE

Force carrier: Force carrier: The PhotonThe Photon

Keep electrons in the Keep electrons in the atoms.atoms.Electricity, light, Electricity, light, radiowaves ….radiowaves ….

The forces in natureThe forces in nature

THE STRONG FORCETHE STRONG FORCE

Force carrier: Force carrier: The GluonThe Gluon

Make protons and neutrons stick Make protons and neutrons stick together.together.Make quarks stick together. Make quarks stick together.

THE WEAK FORCETHE WEAK FORCEForce carrier: Force carrier: The W & ZThe W & Z

Cause some radioactive decays.Cause some radioactive decays.Important for the processes in the Important for the processes in the sun. sun.

Nucleus

Proton

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The Large Hadron Collider (LHC)The Large Hadron Collider (LHC)

The 27 km long Large Hadron Collider accelerates protons to 99,999999991% of the speed of light.

In four places the proton beams are made to collide and the collisions are studied by experiments. There are up to one billion collisions per second. The stored energy in one beam is 360 MJ. ( 360MJ ~ energy of a train travelling at 150 km/h or of an explosion of 77 kg of TNT).


In the LHC accelerator tunnelIn the LHC accelerator tunnel


The magnets that bend the The magnets that bend the proton beams.proton beams.

Magnetic field:8.3 Tesla

1232 dipolemagnets

15 m long35 ton heavy

120 tonnes ofliquid helium

(1.9 K)

Current:11800 Ampere


The building of the LHCThe building of the LHC


10 September 2008 – Champagne !10 September 2008 – Champagne !


19 September 2008 – Hangover !19 September 2008 – Hangover !

A shortcut burned a hole in the helium enclosure and a pressure wave damaged about 50 magnets. Several tonnes of liquid helium leaked out.


Same procedure as last year !Same procedure as last year !

So far no explosions….. And a new world record in collision energy ( 7 TeV).

However, only half of the designed collision energy in 2010 and a collision rate (luminosity) that is 17,000 times lower than the design target.

First collisions in ATLAS on

the 23rd of November

2009.


Experiments at the LHCExperiments at the LHC

ATLAS

CMS

LHCb

ALICE

CERN

Experiments

ATLAS: Proton-proton collisions

CMS:Proton-protoncollisions

ALICE:Atom-atomcollisions

LHCb:Proton-protoncollisions giving b quarks

CERN


Detection of particlesDetection of particles

TrackingDetector

Electromagneticcalorimeter

Hadroniccalorimeter

MuonDetector

Photons

Electrons

Muons

ProtonsPions

Neutrons

Inner layer Outer layer


The ATLAS experimentThe ATLAS experimentThe ATLAS ExperimentSize: 44 by 22 mWeight: 6000 tonnesThe collaboration 2900 physicists(173 Univ., 37

Countries)(Melbourne & Sydney)

Muon detector Hadron calorimeter

Electromagnetic calorimeter Tracking detector


ATLAS in the moviesATLAS in the movies

18


A simulated collision in ATLASA simulated collision in ATLAS

LHC

Protonbunch

LHC

Protonbunch


A real collision in ATLASA real collision in ATLAS


Physics studies: Physics studies: The Higgs particleThe Higgs particle

H

Z Z

e+ e-+ -

p p

Short lifetime

Short lifetime

Long lifetime


Black HoleSignature:

Many particles and particles with a high

energy and with a large angle with respect to the

proton direction.

The holes will disappear after 10-26s according to the theory(if they are produced).

Physics studies: Physics studies: Black holes Black holes


Black holes = The end of the world ?Black holes = The end of the world ?

Energy spectrum

Cosmic radiation

LHC

There are protons in the cosmic radiations with a higher energy

than what can be produced by LHC. The number of collisions at LHC during one

year corresponds to about 1000-10,000

years of collisions in the atmosphere.


The rotational speed of stars in some galaxies are too high to be explained by the known matter.

This unknown matter could consist of new particles that can be discovered in ATLAS.

Dark Matter

Dark EnergyThe universe is not expanding with a constant speed. It seems that there is an unknown repulsive force between the galaxies. This force is thought to be caused by a mysterious dark energy.

What other problems remain to be solved ?What other problems remain to be solved ?


What is dark energy ? What is dark matter? What happened with the anti-matter ? How does particles obtain their mass ?

(Higgs ?) Why is the gravitation so weak ? (Extra dimensions ? Black holes ?) Are the different forces the same thing ?

LHC can

perh

aps

give th

e answ

erWhat problems remain to be solved ?What problems remain to be solved ?


Spin off technology ….Spin off technology ….

o Computer technologyo The World Wide Webo The Computer Grid

o Detector technologyo Radiation treatmentso Medical instrumentation

o Nuclear waste disposalo Transmutation

o Superconducting magnets

o Electronicso ......


The World Wide WebThe World Wide Web

The worlds first web-server. Tim Berners-Lee, the inventor of the World Wide Web.

The most important spin-off from particle physics is the World Wide Web. It was invented at CERN as a way for physicists to share information on computers in different countries.


The next large computer project The next large computer project is the grid.is the grid.

The Worldwide LHC Computing Grid has been developed in order for physicist around the world to have sufficient computer power and in order for them to get hold of the 15 million Gigabytes of data that the LHC will produce each year.


Finally, the most common question…Finally, the most common question…

All this sounds very complicated and expensive, but what is the purpose of the whole thing ? Of what practical use is this research ?

There are two main answers to this question:1. Michael Faraday in 1830 to Queen Victoria: Madam, of what use is a

baby (30 years later: Maxwell, 70 years later: Marconi)

2. We will (probably) never have any practical use of this basic research !

The main purpose is to understand the world we live in in the same way as the pictures from the Hubble telescope give us new knowledge that has no practical applications. The Sombrero galaxy (Hubble telescope)

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Vincent Hedberg - Lund University1 LHC & ATLAS The largest particle physics experiment in the world