particle physics and the mysteries of the early universe cristina lazzeroni royal society university...
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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
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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