Particle Physics and the mysteriesof the early Universe

Cristina LazzeroniRoyal Society University FellowUniversity of Birmingham

100 million x Sun’s Temperature

Over 12 billion years ago, the Big Bang gave birth to the Universe, creating space, time, energy and matter.To understand the laws of the universe, particle physicists want to recreate conditions of less of billionth of second after the Big Bang

Useaccelerators !

Particles accelerated to speed of light :

Protons smashing together can produce all sortsof particles, seen in the earliest moments of the universe

E = Mc2

E = h h = Plank constantParticle-wave equivalence

Large Hadron Collider (LHC)

Protons, accelerated by 7

trillion volts, travel at 0.999999991

speed of light and smash together

600 million times/sec

proton=hadron French-Swissboarder

27 km ring,

Beam spot

needle eye=0.3 mm diameter

beam = 0.03 mm diameter at focus

magnets cooled to 1.9 K, colder than outer space

The ‘Large Hadron Collider’ accelerates 2800 bunches,1011 protons per bunch, at 7 TeV

This corresponds to:

350 MJ stored energy per proton beam= Kinetic energy of 1200 elephants running at 25 mph= Kinetic energy of family car travelling at 1000 mph= Kinetic energy of fully loaded Airbus A320 at landing speed= Enough energy to melt 550 kg copper

TOTAL ENERGY STORED in LHC superconducting

magnets: 10 GJ = “An avalanche”

(10000 t of snow, sliding down 100 m)

Rutherford’s Experiment in 1909

particle

Found:

size: Nucleus Fly Atom Cathedral

‘like a fly in a cathedral’

=

New model of atom:

particlenucleus

electron

particle

Expected:

cake tin, football, ping pong balls

Ordinary matter is made of fermions, held together by bosons

Photons and gluons are ripples in the (EM, strong) fields - quantum fields

Z,W : Weak force carriers

matter particle

force particle

Overall there are 6 quarks, 6 leptons, 4 force carriers

top quark

ZW

. . .e e u d s c b

All nice, simple, understood ?!

xx

x

xxx

x

xx xxx

x

W

e

t

There should be something (new particle)in the universe that gives mass to all particles

Higgs ParticlesHiggs Particles

Higgs field :particle mass is a measure of the resistance to

movements through this field

Mass is really a measure of how difficult it is to accelerate an object (F=ma)

Higgs field - magnetic field

Buridan’s DonkeyPhoton, W+, W- masslessmeta-stable

Photon masslessW+,W- massiveasymmetric

The “Mexican hat” : radial symmetry

A ball at the top of the ‘hat’ can fall down in

any direction, all equally probable.

When it does fall, a particular direction is

chosen and the symmetry is broken

The interesting events are very rare: 1 in 100,000,000,000 (1 followed by 11 zeros)

Equivalent to looking for one particular grain in 2.5 million kg of rice

Higgs events are rare

Since then, many observations done but mechanism/origin not yet clear

Cambridge, 1928 :

( ) 0=−∂ ψγ μμ mcih

Special Relativity

Quantum Mechanics

The Dirac Equation

Dirac predicted the existence

of the positron e+, same mass

but opposite charge to e-

Matter and Anti-matter

Equal quantities of Matter and Anti-matter should have been

produced in the Big Bang, then annihilated each other

leaving just radiation

Escher images

Antimatter in the story of

In the Angels and Demons story, the bad guys go to a laboratory called “CERN”.

They steal half a gram of antimatter in a canister, which they then take to Rome to use as a bomb.

A feather weigths about ½ gram.

TM & © 2009 Columbia Pictures Industries, Inc. All Rights Reserved.

TM & © 2009 Columbia Pictures Industries, Inc. All Rights Reserved.

If We Could Accumulate It

If we had some means to accumulate half a gram and if we could put it in a container and if we could transport it safely to another site,

it would indeed be a powerful bomb as in

TM & © 2009 Columbia Pictures Industries, Inc. All Rights Reserved.

How Long to Get Half a Gram?

If LHC could somehow accumulate all the antimatter it produced,

it would take 10 million years to get ½ a gram of antimatter

All the antimatter produced in accelerators annihilates within a fraction of a second.

Supersymmetry: symmetry between types of particles.

Every observed particle has a superpartner, just too massive to have been already seen

How many spacetime dimensions? No reasons why they should be 3 ... apart from observational reasons !

New dimensions can be small

Or impossible to detect :

Particles would become extended objects

How are particles detected? See our exhibition of working detectors, LHC data taking and many other activities, including a new computer game !

World’s most massive “onion” structure to

capture the particles

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ATLAS Control Room, first beams, 20 November 2009

~ 10-45 tracks with pT >150 MeV per vertexVertex z-positions : −3.2, −2.3, 0.5, 1.9 cm (vertex resolution better than ~200 μm)

Event with 4 pp interactions in the same bunch-crossing

Max peak luminosity: L~1.6 x 1030 cm-2s-1

average number of pp interactions per bunch-crossing: up to 1.3 “pile-up” (~40% of the events have > 1 pp interaction per crossing)

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Integrated luminosity vs time(from first √s =7 TeV collisions on 30 March 2010 to beginning of ICHEP on 22 July)

(stable beams)

1st W

1st top-quark candidate

1st Z

2.55 TeV mass di-jet event

29

First searches for New Physics

Exciting times ahead !Stay tuned and ...

be prepared for surprises !

Questions ?

And don’t forget the exhibition in the Bridge Study room !!

Spares

LHC Magnets store even more energy

• 1232 superconducting Dipoles,1.9 K, 8.33 Tesla• ~400 superconducting Quadrupoles• ~6000 superconducting corrector magnets• TOTAL ENERGY STORED in LHC superconducting magnets:

– 10 GJ = “An avalanche”

(10000 t of snow, sliding down

100 m)

BenefitsFirst, the new knowledge.

Also, the technology is pushed to the limitsand produces many practical applications

Most of the 17000 particle accelerators are used in medicine for cancer treatment

Particle detectors are used in medical imaging

Then the computing : the world wide web !And soon the GRID

Physicists think that with very high energy beams

forces start to behave the same

as if there is just one force, not several forces

“Do all the forces

become one ?”

• Primary cosmic ray in upper atmosphere

• Collision with nucleus• Initiates “cascade”

– Secondary cosmic rays

(pions that decay into muons, electrons and neutrinos)

– Higher energy primary• larger secondary shower

• Time dilation effects:

muons arrive at ground level

The Spark Chamber is a triggered device

Scintillationcounter S1 Photo-tube 1

Delay(cables)

CoincidenceUnit

Photo-tube 2S2

Trigger Unit

HV Supply

Particletrack

Detecting Particles

Used Bubble Chambers up to 1970s

•Only 1 event / second•Photos scanned by hand•No selection on events

How does the presence of matter change space and time?

It bends like a rubber sheet It makes time go slower

the Universe was born withequal amounts of matter and

antimatter

0=t

CP violation : (and B violation and phase transitions)

the Universe containsslightly more matter than

antimattersec1~ t

Particles and anti-particles annihilate :

the Universe contains only matter (and lots of photons)

sec1~t

The Quark-Gluon Plasma

Normal hadronic matter

At extreme temperatures and/or densities hadronic matter ‘melts’ into a plasma of free quarks and gluons.

Strong Force: how does it generate 98% of the mass of nuclear matter? why are there no free quarks? unlock the secrets of the primordial state of matter, the Quark-Gluon Plasma, which would have existed up until about 10 millionths of a second after the Big Bang, and could be created in the core of collapsing neutron stars

How to Make a QGP

• Need very high energy densities

• Create sub-atomic volumes of hot, dense matter similar to conditions 10-6s after Big Bang

• Fireball must live long enough for phase transition to take place

• Collide lead ions (lead nuclei) at highest energies

The Fireball

• Temperature of our fireball ~ 1013K i.e. > 1,000,000 times the temp of centre of Sun.

• Density ~ Great Pyramids crushed to the size of a pin-head – similar to neutron star densities (but much hotter!)

T ~ 15,000,000 K

What Happens ?

• Energy is converted into many quarks, anti-quarks and gluons.

• QGP lasts for about 10-22 seconds

• Then thousands of particles are produced

We have to study the QGP from this!

Only a small fraction of the total is ordinary matter that we know

Feynman diagrams

Trees Penguins

46

10,000,000,001 10,000,000,000

We are lucky because…

Immediately after the Big Bang,the matter and antimatter… were NOT exactly equal

Matter Antimatter

Notice

The Great Annihilation followed !!!

radioactive decays

holding proton, nucleus

gluons

Weak Force

Strong Force

Enrico Fermi(1901 - 1954)

neutron decay

Size of nuclei is set by strength of strong force

How stars generate energy

Photon, W+, W- masslessmeta-stable

Photon masslessW+,W- massiveasymmetric

Mexican hat: angular symmetry