1. 27 km ring Large Hadron Collider went online on Sept. 10 2008
Counter propagating proton beams accelerated to 7x1012 eV make 11,000 revolutions per second and collide in four points

2. 1600 superconducting magnets are cooled to 2 K by 96 tons of liquid helium
CMS detector

3. Era of Discovery with CMS Detector
TAMU Group
Teruki Kamon, Alexei Safonov, David Toback
Special Colloquium, LHC…
Alexei Safonov
09/17/08 (Next Wednesday)

4. The signal : jets + leptons + missing Energy

5. LHC Days… We will try to understand:
The mechanism for generating masses
The physics behind the scale of W, Z boson mass scale
~ electroweak scale
Mplanck>>MW
Do we have any further evidence of grand unification?
The origin of dark matter
Is there any particle physics connection?
From B. Dutta’s talk 5
Precision Cosmology at the LHC

7. Quantum Fields
From R. Fries’ talk
M. Planck (1900) suggested that energy in light comes in small packets called ‘quanta’.
These quantum packets behave like particles.
The electromagnetic field can be described by the action of these force carrier particles, called photons .
Energy of one quantum
 = frequency
Photons are bosons with spin 1 and they are massless. They ‘couple’ to electric charges and have no electric charge themselves.
Force carriers transmit forces by being exchanged between particles.
Feynman diagrams
Electron + proton
interacting
Electron-positron
annihilation
Particles and Forces

8. Electroweak Force
It could be shown that the weak force and the electromagnetic force are two aspects of one unified electroweak force.
There are 3 spin-1 bosons which are force carriers of the weak force, the W+, W– and Z0 bosons which are very heavy. They couple to all fermions.
Feynman diagram
for muon decay
Boson with mass 0 (e.g. photon):
force ~ 1/distance2, infinite range
W,Z bosons with large mass:
Force acts only over distance < 0.01 fm
Particles and Forces

9. Quarks
1968 a Rutherford-like experiment (deep inelastic scattering) confirmed that there are indeed quarks inside a proton.
1st generation
2nd generation
3rd generation
There are six quarks in 3 generations:
(up,down)
(charm, strange)
(top,bottom)
+ their six antiquarks
Increasing mass from GeV (up) to 174 GeV (top).
Surprise: they have fractional electric charges +2/3 or -1/3. They feel both the
weak and strong force.
Particles and Forces

10. Gluons p + The strong interaction between quarks through
exchange of another spin-1 boson: the gluon g.
‘Charges’ for the strong force are called color
charges. There are three of them and each quark can carry all 3:
‘red’, ‘green’ and ‘blue’ (+ 3 anti colors for antiquarks)
Gluons couple to the color of a particle.
Careful: this is not the same as color in common language!
Two kind of hadrons (‘quark atoms’) exist:
Quark + Antiquark = Meson
(e.g. pions)
3 Quarks = Baryon
(e.g. proton, neutron) p
Hadron are color neutral:
Colors of the quarks add
up to ‘white’
Particles and Forces +

11. Matter is effected by forces or interactions (the terms are interchangeable)
There are four fundamental forces in the Universe:
gravitation (between particles with mass)
electromagnetic (between particles with charge)
strong nuclear force (between quarks)
weak nuclear force (that changes quark types)

12. The Standard Model + Higgs boson
The Standard Model (SM) describes all these particles and 3 of 4 forces. We have confirmed the existence of those in the laboratory experiments.
+ Higgs boson
Higgs has not yet been discovered
The mass is constrained from LEP
and Tevatron data:
114 GeV<MH<154 GeV 12
Precision Cosmology at the LHC

13. The Higgs Boson
One particle is left to discuss: the Higgs Boson is part of the Standard Model, but it is very special.
Higgs Mechanism:
A field fills all of space because of a mechanism called spontaneous symmetry breaking. It ‘sticks’ to particles, making it ‘harder for them to move’. This is what gives quarks and leptons their mass.
Spontaneous symmetry breaking
Similar to the
celebrity effect in a crowd.
Particle
As a consequence, there should also be a spin-0 boson, the Higgs boson.
It has not been found yet.
Physics H
Particles and Forces
Credit: CERN

14. DARK MATTER

15. Orbital Motion in the Milky Way
Differential Rotation
Sun orbits around Galactic center with 220 km/s
1 orbit takes approx. 240 million years
Stars closer to the galactic center orbit faster
Stars farther out orbit more slowly

17. Matter extends beyond the visible disk!

18. There is much more matter than we see!

19. Dark matter dominates in all galaxies! > 90% of mass is invisible
Dark matter halo

20. "spherical bastards”
Fritz Zwicky
Walter Baade

22. What is dark matter??? White dwarfs Brown dwarfs Black holes
Neutrinoes
???
Revision of the Standard Model seems to be necessary

23. The Early History of the Universe (2)
25% of mass in helium 75% in hydrogen
Protons and neutrons form a few helium nuclei; the rest of protons remain as hydrogen nuclei
No stable nuclei with 5 and 8 protons
 Almost no elements heavier than helium are produced.

24. Figure 15.14: This graph plots the abundance of deuterium and lithium-7 versus the present density of the universe. Observations of the abundance of deuterium and lithium-7 are uncertain, but they limit the density of normal matter in the universe to a narrow range (green bar). The density of normal matter cannot be more than 5 percent of the critical density ρo.

25. The Nature of Dark Matter
Can dark matter be composed of normal matter?
If so, then its mass would mostly come from protons and neutrons = baryons
The density of baryons right after the big bang leaves a unique imprint in the abundances of deuterium and lithium.
Density of baryonic matter is only ~ 4 % of critical density.
Most dark matter must be non-baryonic!