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

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

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

The signal : jets + leptons + missing Energy

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

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

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

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 0.002 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

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 +

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)

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

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

DARK MATTER

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

Matter extends beyond the visible disk!

There is much more matter than we see!

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

"spherical bastards” Fritz Zwicky 1898-1974 Walter Baade 1893-1960

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

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.

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.

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!