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Invasions in Particle PhysicsInvasions in Particle Physics

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Invasions?

“Gentlemen we are being invaded: the accelerators are here”

L.Leprince-Ringuet

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High energy particles have extremely small wavelengths and can probe subatomic distances: high energy particle accelerators serve as super-microscopes.

The higher the energy the closer particles can come to each other, revealing the smaller details of their structure.

The energy of the collisions produces new particles : E=mc 2 The higher the energy the heavier the new particles that can be created.

Particle Physics - High Energy PhysicsParticle Physics - High Energy Physics

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like smashing two cars together

and getting a bulldozer out

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2121stst century particle physics century particle physics

(e.g.) Fermilab’s Tevatron is the highest energy accelerator in the world today.

Beams of protons collide with beams of antiprotonsantiprotons

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antimatter

particle accelerators create antimatter by smashing high energy particles onto metals

the total amount of antimatter produced in particle accelerators per year ~ 1 microgram

even one microgram of antimatter would provide enough energy to drive your car for a month (E=mc2)

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no mass?no mass?

Yes, photons are massless

We thought neutrinos were massless too

In 1998 underground experiments discovered that neutrinos have tiny masses

The SNO detector is more than a mile underground

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extra dimensions?6?7?32?

String theory demands extra String theory demands extra dimensions.dimensions.

ExperimentsExperiments can actually can actually discover them!discover them!

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In 1905 Victor Hess performed a series of high-altitude balloon experiments and found ionizing radiation the origin of which is beyond the Earth’s atmosphere.

Cosmic rays were the only source of high energy particles to study until accelerators were developed.

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Where does this proton come from?

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one possible source of such high-energy protons:

two rings of high-energy particles created from matter from the supernovae remnant falling towards the black hole.

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detection of high energy particles

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The chamber creates a volume of supersaturated alcohol vapor that condenses on ions left in the wake of charged particles. This is accomplished by establishing a steep vertical temperature gradient with dry ice. Alcohol evaporates from the warm top side and diffuses toward the cold bottom. A layer of supersaturation is created near the chamber bottom. Tracks of alcohol droplets indicate trajectories of charged particles, since each ion becomes a nucleation site for droplet condensation.

CLOUD (WILSON) CHAMBER

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particle tracks left in a photographic emulsion during the decay of a pion.

The pion enters moving upwards and comes to rest.

It decays to produce a muon, which travels to the right.

The muon then decays to an electron, producing the final track leaving at the top right.

electron (e)

The pion was discovered by Cecil Powel and Giuseppe Occhialini in 1947 using photographic emulsions at the Pic du Midi, high in the French Pyrrenees.

the pion

p.s. e, are leptons

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Pion picture in a streamer chamber; gas glows brightly along the tracks of the particles.

e

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Strange Particles

All of these strange particles were unstable.

Their origin and purpose was an entire mystery.

There were two kinds of them: one kind whose decay products included always a proton were called hyperons and one kind

whose decay products only consisted of pions were called kaons.

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“ I remember in 1949, on a bulletin board at the Princeton Institute for Advanced Study, a photomicrograph of a nuclear emulsion event, showing what is now known a a K-meson decaying into three pions. We all saw it. No doubt that something interesting was going on, very different from what was then known, but it was hardly discussed because no one knew what to do with it”

Jack SteinbergerJack Steinberger

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Wideroe Principle:

The Norwegian Rolf Wideröe realized that, if the phase of the alternating voltage changed by 180 degrees during a particle’s trip between gaps, the particle could gain energy in each gap. The idea of the linear accelerator was born.

linear accelerators

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11stst circular accelerator circular accelerator (11 inches!)(11 inches!)

uses both electric and uses both electric and magnetic fields.magnetic fields.

particles orbit in circlesparticles orbit in circles

Lawrence and Livingston built the Lawrence and Livingston built the first cyclotron in 1932. It was about first cyclotron in 1932. It was about 30 cm across, in a magnetic field of 30 cm across, in a magnetic field of about 5000 Gauss and accelerated about 5000 Gauss and accelerated protons to roughly 1.2 MeVprotons to roughly 1.2 MeV

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professor’s view

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mechanical engineer’s view

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computer scientist’s view

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theoretical physicist’s view

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visitor’s view

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LBL

McMillanLawrence

Synchro-cyclotron, Betatron, synchrotron

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3 GeV protons Brookhaven National Laboratory(1952)

Cosmotron

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Strong Focusing (1952)

Colliding Beams (60s)

Superconducting magnets (80s)

Stochastic Cooling (80s)

major invasions in accelerator technology

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P2K/NASATV movie excerpt

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After the pion a plethora of new particles calledhadrons were discovered in accelerators

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strangeness name uud udd S=0 nucleon

uusudsdds S=-1 sigma

ussdssS=-2 cascade (ksi)

The baryon octetThe baryon octet

pp nn

strangness then is counting how many strange quarks are in these hadronsstrangness then is counting how many strange quarks are in these hadrons

All hadrons are made of quarksAll hadrons are made of quarks

up quark : u down quark : d strange quark : sup quark : u down quark : d strange quark : s

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quarks have not been seen as isolated particles.

when you smash hadrons at high energies where you expect a quark, what you observe downstream is a lot more hadrons, NOT fractionally charged quarks.

this spray of hadrons is called “jet”

Gell-Man 1964:

““A search for stable quarks… and/or stableA search for stable quarks… and/or stabledi-quarks … at the highest energy accelerators would help to di-quarks … at the highest energy accelerators would help to

reassure us of the non-existence of real quarksreassure us of the non-existence of real quarks”

quarks

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the Big picture the Big picture

The universe is made out of matter particles and held together by force particles

fermionsbosons

quarksleptons

gaugebosons

graviton

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Feynman GraphFeynman Graph

The electron and quark interact electromagnetically by the exchange of a photon. The lines, wiggles and vertices represent a mathematical term in the calculation of the interaction.

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Quantum WeirdnessQuantum Weirdness The interactions of particles obey the rules of quantum mechanic and of special relativity

And particles aren’t really particles, they are quantum quantum fieldsfields

The fermions (quarks and leptons) are especially weird…

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G u e s sG u e s s

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the Modelthe Model

After 50 years of effort, we have a quantum theory which explains preciselyprecisely how all of the matter particles interact via all of the forces — except gravity.

For gravity, we still use Einstein’s General Relativity, a classical theory that has worked pretty well because gravity effects are so weak.

What is a model?

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the Standard Modelthe Standard Model a list of particles with their “quantum numbers”, about 20 numbers that specify the strength of the

various particle interactions, a mathematical formula that you could write on a

napkin.

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what does the Standard Model explain ?what does the Standard Model explain ?

your body atoms electrons protons, neutrons quarks

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what does the Standard Model explain ?what does the Standard Model explain ?

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neutrino (neutrino () sky) sky

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what does the Standard Model explain ?what does the Standard Model explain ?

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what does the Standard Model what does the Standard Model notnot explain ? explain ?

HST image of an 800 light-year wide spiral shaped disk of dust fueling a 1.2x10^9 solar mass black hole in the center of NGC 4261

quantum gravity

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what does the Standard Model what does the Standard Model notnot explain ? explain ?

quantum gravity

dark matter and dark energy

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what does the Standard Model what does the Standard Model notnot explain ? explain ?

quantum gravity

dark matter and dark energy

Higgs

Arrange it so delicately that it will fall down in 19 minutes.

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the Bigger Big picturethe Bigger Big picture

The Standard Model describes everything that we have The Standard Model describes everything that we have seen to extreme accuracy. seen to extreme accuracy.

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Now we want to extend the model to higher energies and get the whole picture

the Bigger Big picturethe Bigger Big picture

For this we need new experiments and ideas

supersymmetry

strings

strings

(even) extra dimensions

(even) extra dimensions

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matter matter antimatterantimatterDirac (1928)

special relativity & quantum mechanics

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fermions fermions bosonsbosonssupersymmetry (SUSY)supersymmetry (SUSY)

every particle has a superpartner particle

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fermions fermions bosonsbosonssupersymmetrysupersymmetry

every particle has a superpartner particle

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fermions fermions bosonsbosonssupersymmetrysupersymmetry

electron electron sselectronelectron

quark quark ssquarkquarkphotphotinoino photonphoton

gravitgravitinoino gravitongraviton

most of the dark matter in the universe maybethe lightest sparticle

none of the sparticles have been discovered yet

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HST image of an 800 light-year wide spiral shaped disk of dust fueling a 1.2x10^9 solar mass black hole in the center of NGC 4261

quantum gravity

what do explain ?what do explain ?

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require 7 extra space dimensions and give us ways to hide them

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compactificationcompactification

brane-worldsbrane-worlds

Standard Model particles are trapped on a brane and Standard Model particles are trapped on a brane and can’t move in the extra dimensionscan’t move in the extra dimensions

There could be There could be other branes which other branes which would look like would look like dark matter to usdark matter to us

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how do we see a hidden dimension?how do we see a hidden dimension?

? what particles can move in that dimension

? how big is that dimension

? what is its shape

some dimensions are easier to detect than others

slice of a 6 dimensional Calabi-Yau space

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gravitonsgravitonsare the most robust probe of extra dimensions

gravity is so weak that we have never even seen a graviton.

The gravitational attraction between two electrons is about 1042 times smaller than the electromagnetic repulsion.

F=GF=GNN

melectronmelectron

r2

rmelectron melectron

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it gets stronger at lower energies ifthere are extra dimensions….

think about this:

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gluon (becomes“jet” of hadrons)

graviton

quark

antiquark

…in which case high energy gravitons may be produced in collider experiments:

these gravitons probably “escape”these gravitons probably “escape”into the extra dimension(s) into the extra dimension(s)

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graviton emission simulation: we don’t see the graviton we see a jet from the gluon

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Collider Detector at Fermilab

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concentric cylindrical layers

energy deposited from the particle debrisof the collision in the middle

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“lego” event display

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Two events are graviton simulation and one is real CDF data: Can youpick the gravitons?

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two events are real CDFdata and one is gravitonsimulation; Can youpick the graviton?

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01χ~

01χ~

gluino and squark particles:production and decays

supersymmetry at colliders

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e.g.SUSY candidate event at CDF

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Higgs simulation

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new accelerators for new physics

Linear Collider (?,~2012)

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underground and in the sky

SuperNova Acceleration Probe (SNAP)

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underground and in the sky

KamLAND neutrino detector

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The coming invasions in particle physics, cosmology and astrophysics will answer (among many other questions)

what is the physics that connects the gravitational scale and the scale of the typical mass of the elementary particles

what is dark energy and what is dark matter

do protons decay

what is string theory

what are the dimensions and dynamics behind spacetime

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