Fermilab Public Lecture

The LHC Voyage

Discovery

Dan Green

Fermilab

Fermilab Lecture, Sept. 23, 2011

What is Particle Physics?Particle physics is the modern name for the centuries old effort to understand the laws of nature. It aims to answer the two following questions:

What are the elementary constituents of matter ?What are the forces that control their behavior at the most basic

level?Physicists continue to ask these questions since they have never

really grown up.

Experimentally:

Make particles interact (accelerators) and study the produced particles. E=Mc2, using collision energy to make new, heavy

particles.

Measure the energy, the direction and the identity of all these reaction products as precisely as possible (detectors).

What is the Universe Made of?

Early speculation on the building blocks, 500 BC

Atoms and Simplicity, 1869

All the complexity that we see in the World, with it’s 92 elements, comes from the simplicity of arranging electrons and protons in atoms. The periodic table groups elements with equal number of outer orbital electrons, for example noble gases. Lesson: predictions for missing elements.

Electrons - 1897

Accelerate in electric field, deflect in magnetic field and observe by having the e interact in a detector – the basic steps. Lesson: We can see electrons with our own eyes!

Nuclei – Rutherford, 1908• Rutherford established the

structure of the atom • by scattering particles off

the atoms, • seeing wide angle

deflections in a detector• Lesson: infer structure by

scattering. • Atoms have small, positively

charged nuclei, 100,000 times smaller than the electron distribution!

• Students and scintillation……

Going Smaller and SimplerNuclei are all made up of just neutrons and protons. Looking more closely, they in turn are made up of quarks. Quarks are fundamental ! ?

To look closer we need higher energies. We use E = mc2 (Einstein) and we quote mass in energy units.

What are the Forces ? - Gravity

“Of Newton with his prism …. A mind for ever voyaging through

strange seas of thought”.

Sir Isaac Newton

“I seem to have been only like a boy playing on the seashore, and

diverting myself in now and then finding a smoother pebble or a

prettier shell than ordinary, whilst the great ocean of truth lay all

undiscovered before me.”

Lesson: gravity is universal – on earth (apples) as in the heavens

(satellites) – a unification!Fermilab Lecture, Sept. 23, 2011

Electricity-Magnetism

Maxwell in 1862 unified electricity and magnetism, and in so doing predicted a wave going at the speed of light, thus explaining light. Lesson: unification may predict new phenomena.

The “Weak” InteractionCurie in 1895 discovered that the elements were not eternal and indivisible, but changes occurred by “radioactive decay”. Elements can be transmuted !

Much later, 1982, we found that the weak interaction and the electromagnetic were unified. Lesson: forces tend to unify at high energies/temperatures or short distances .

Interactions in the Standard Model

Matter particles interact via the exchange of force particles

boomerang?

Nuclei- need a strong interaction to overcome coulomb repulsion of the protons. “Gluons” are the force carriers

The “Standard Model” - SMM

les Force Particles

You are here

All force carriers, photon (EM), gluons (strong), gravitons (gravity) are massless EXCEPT the W,Z (weak force) – why is that? The LHC was designed to find the answer.

Predictions:b, t, vτ seen at Fermilab

Is the SM the End of the Story?In the SM all particles have no mass, like the photon, and move at the speed of light! Not… So we postulate the “Higgs boson” which gives mass to each particle of the SM.Without a Higgs boson, our calculations for collisions begin to fail at a mass around 1 Trillion eV (TeV). This defines the “terascale” of mass – the TeV scale – where new Physics must emerge.The Higgs by itself is not enough. Postulate a “super-symmetry” to solve the remaining problems of the Higgs. What about our inability to incorporate quantum gravity? Postulate 10 dimensions! More later.What about Dark Matter and Dark Energy – which are 96% of the Universe by weight? No Standard Model particles exists to explain them. Oh my!

Why the LHC ? Many of the Standard Model problems point to the mass scale of 1 TeV. The Large Hadron Collider, LHC, at CERN, in Geneva Switzerland was designed specifically to decisively confront that mass scale.It is Large, 26 km circumference, uses Hadrons, protons in this case, and it is a Collider, bashing protons on protons head on = LHC.

Geneva airport

Particle Accelerators and the LHC

de Broglie

High energies allow us:

To look deeper into Nature (E 1/size), (“powerful microscopes”)

Einstein

To discover new particles with high(er) mass (E = mc2)

Boltzmann

To study the early universe (E= kT)

Revisit the earlier, hotter, history of our Universe , searching for a new simplicity (“powerful telescopes”) by observing phenomena and particles no longer observable in our everyday experience.

The History of Our Universe

proton-proton collisions at the LHC correspond to conditions here; time, temp and energy. The LHC is a time machine!

Fermilab Lecture, Sept. 23, 2011time

energy,temp

The LHC Beams are Energetic

The LHC and its experiments are arguably the most complex scientific instruments ever built – of necessity if we are to confront the TeV mass scale decisively.

The energy stored in the LHC beams would melt 1T of Cu. This is 200 times the Tevatron total beam energy. The energy in the magnets would melt 50T of Cu. Caution is needed.

The LHC is a Big Step in Mass

The gain in “mass reach” is not just the factor of 3.5 in proton energy w.r.t. Tevatron. At the interesting TeV mass scale the reaction rate is a factor at least 10000 x greater at the LHC than at the Tevatron. Truly, the LHC is a machine for discovery, aimed at the TeV mass.

LHC Accelerator - Poised for Discovery

The LHC at 1.9 K is colder than the CMB

• The LHC is the highest energy collider in the world

• The LHC has the worlds largest cryogenic plant.

• The LHC is designed to have the highest reaction rate of any collider, design value is 1 GHz.

wrt Tevatron (at design)Energy x 7 Reaction rate x 20Large increase -> discovery

World’s Largest Cryogenic Plant

Deep space is at 2.3o above absolute zero. LHC operates at 1.8o to achieve a higher magnetic field. If normal magnets used, size would be 4x and power used would be 40x!

Extremely High Vacuum

“Store” beams for ~ 10 hours. Protons travel ~ 10 billion km around the LHC ring ~ round trip to Pluto -> need a good vacuum

It’s Difficult – Rare Processes

At design operation, there are 1 billion interactions per second to examine. In order to decisively study the 1 TeV mass scale, we need to examine a total of 10,000 trillion interactions. We are only 1 % of the way there at present and at ½ the design energy. We are just starting the long voyage.

ATLAS and CMS – at the Leading Edge

Each detector is like a 100 megapixel camera which takes 40 million pictures per second. The largest and most complex scientific instruments ever built.

World’s Largest Collaborations

There are 4 experiments at the LHC. The 2 general purpose detectors, ATLAS and CMS, have formed the largest scientific collaborations ever attempted. They function well because they have a common language and goals – Physics.

The CMS Collaboration

CMS CollaborationUSAAustriaBelgiumFinland FranceGermanyGreeceHungaryItalyPolandPortugalSlovakiaSpainCERNSwitzerlandUKRussiaArmeniaBelarusBulgariaChinaCroatiaCyprusEstoniaGeorgiaIndiaKoreaPakistanTurkeyUkraineUzbekistan

31 Countries146 Institutes1801 Physicists and Engineers

The US is the largest national group in CMS – about 1/3. FNAL is the second largest group in CMS, second only to CERN. FNAL is also the host for US CMS

It takes a collaboration of this size to fully address the physics.

US Physics and the LHC

CMS – Timeline, “Laying the Keel”

It took almost 20 years to design, construct, test, install and commission CMS with a very large team of scientists and engineers. 1993 - 2003

CMS Magnet

The most expensive single device in CMS. The world’s largest solenoid.

The magnet is like a prism – bending the particles with more energy by less.

Precision Tracking

200 m2 of Si with 75 million channels. A factor > 10 increase in complexity w.r.t. previous experiments. Spatial resolution of 0.0008 “ precisely determines particle trajectories in the magnet and therefore energies.

Crystals – Energy Measurements

More than 60,000 crystals manufactured with <1 % tolerances in response. Needed for precise, redundant measurement of electron energies.

Data Analysis -It Takes a “Grid”

Fermilaboperates the national computing center for US CMS

CMS produces 1 million DVD of data per yearFermilab Lecture, Sept. 23, 2011

How Do FNAL Physicists Participate?

CMS is 4500 miles away. Can we ‘do physics” here? Yes indeed, all physicists are “remote” . At CERN you are 20 km away and the detector is 100m underground and inaccessible. We built the “Remote Operations Center” – ROC - and the “LHC Physics Center” - LPC. Stop by during the reception!

The sun never sets on CMS. ROCs at CERN, DESY/Hamburg, FNAL and IHEP/Beijing.

Underground Experiment Cavern

Late 2004 the “dry dock”

100 m underground

Spectacular Operations – “The Launch”

34Fermilab Lecture, Sept. 23, 2011

World’s Largest Solenoid

4 T, 3 GJ~ 600 kg of TNT stored energy

Feb., 2007

The Press Was There

Looking Back in Time at the LHC

We make, in a tiny region of space, interactions at temperatures a million times hotter than the center of the sun. These temperatures correspond to a time a billionth of a second after the big bang. To set the scale, one TeV is the energy of a flying mosquito – but concentrated into a region of space 10,000 billion times smaller. An enormous energy density.

“The Shallows” – Shakedown Cruise

In 2010, CMS measured all the particles of the Standard Model – some shown here

19601970

Into “Deep Waters”

For every 10,000,000 W events produced you make at most 1 Higgs, which can then decay into 2 Z bosons, for example. It is still early days.

Higgs Decay to Z+Z?What a Higgs decay into 2 Z bosons which subsequently decay into 2 muons each would look like in CMS

http://lbne2-docdb.fnal.gov /0040/004099/002

Into Uncharted Seas

Once past the “shallows” and on into the deeps, what strange beasts may appear….

Terra incognitaFermilab Lecture, Sept. 23, 2011

Dark Matter ?

There is no known candidate for Dark Matter. Dark Matter is a stable, neutral relic particle from the earliest moments after the Big Bang – wonderful new physics.

~ , ~ 1/v r v r

You are here

Dark Matter and Colliding Galaxies

Galaxy has a visible component and a dark component which interacts only gravitationally. Colliding galaxies show the different interactions of the neutral Dark Matter and the visible matter, which has Electromagnetic interactions.

Dark Matter Searches -“Full Court Press”

Produce it Scatter it Observe it LHC FNAL annihilate

These 3 could converge, making a tremendous scientific breakthrough

Super - Symmetry (SUSY)The lightest SUSY particle (LSP) is stable and would explain Dark Matter . A LSP mass of ~ 1 TeV yields the observed relic abundance of Dark Matter particles, 23 % !

SUSY also predicts the Grand Unified Theory (GUT) of forces where the 3 Standard Model forces unify at very high energies..

SUSY doubles the number of particles. Each Standard Model particle has a partner

SUSY at LHCFor all the good features, many physicists like SUSY – but Nature is the final arbiter. A typical SUSY pair in CMS would have large unbalanced momentum (LSP escapes without leaving energy in CMS). Limits at the LHC are approaching 1 TeV. Stay tuned !

Gravity and SM Forces

A completely naïve classical extrapolation of gravity comes close to the GUT mass scale. Is that a hint of more unification?

100 years after GR (Einstein), it appears that point particles are not possible, but rather strings existing in many (10) dimensions, with those > 4 curled up into tiny size.

Gravity is very, very weak – a small magnet can overcome the whole Earth and pick up a nail. Is that because gravity spreads out and dilutes in the additional dimensions?

Gravity ? – Not in the SM• Extra dimensions ?• Are those dimensions observable? At the LHC we will look for

extra dimensions. Perhaps we can push a particle to disappear into the unseen dimensions.

• We are presently setting limits on the mass scale of a few TeV

Forces and Unification

Quantum Gravity

Super Unification

Grand Unification

Electroweak Model

Weak Force

Nuclear Force

Electricity

Magnetism

Maxwell

Short range

Long range

Short range

Terrestrial Gravity

Celestial Gravity

Einstein, NewtonGalilei

Kepler

Long range

Universal Gravitation

Electro magnetism

Weak TheoryStandard

Theories: STRINGS? RELATIVISTIC/QUANTUM CLASSICAL

GUTTOE

Energy

“We shall not cease from exploration and the end of all our exploring will be to arrive where we started and know the place for the first time….A condition of complete simplicity….And all shall be well.” – T.S. Eliot

The LHC program “has legs”. In 2014 the energy will double, opening up a higher mass reach. The interaction rate is planned to increase 10 fold, allowing study of rarer processes – a 25 year program of research has begun.

Well Documented – Read More

Terascale Incognita

We have arrived in “terascale incognita”. The exploration of the TeV mass scale is well underway. By the end of 2012 many possible new phenomena will have been examined decisively. Remember: “Nothing is too wonderful to be true if it be consistent with the laws of Nature” – Michael Faraday.

HEP Invented WWW

Elements of Innovation in Science

Large science projects push innovationSpace: Apollo mission, space station, voyagerParticle physics: accelerators in generalAt CERN: LEP, LHC

Pushing the limits of what is possible. CERN examples: Magnetic fields, vacuum, precision alignment, cryogenicsTransport, displacement of very heavy equipmentHigh density radiation-tolerant silicon detectorsLarge scale industrial control systemsElectronics and computing systemsProject management and coordination

Spinoffs - Accelerators

Magnets (MRI), Superconducting coils, accelerators (e.g. Loma Linda p therapy). Light sources

Accelerators developed in labs are used in hospitals

Courtesy of IBA

Around 9000 of the 17000 accelerators operating in the World today are used for medicine.

Example: Hadron TherapyFermilab Lecture, Sept. 23, 2011

Pathway of an Innovation

Radionuclides used in PET scanning are produced by cyclotrons in hospitals – glucose labeled with positron emitters e.g. Fluorine 18.PET cameras today use APDs (and Si PMs) and heavy scintillating crystals and starting to be combined with MRI scanner.

The scientific basis for all medical imaging (functional & physiological) are steeped in nuclear/particle physics

1928: description of electrons consistent with Einstein’s special theory of relativity and quantum mechanicsPredicted existence of anti-particles (e.g. positron - basis of Positron Emission Tomography (PET)) and explained spin (- basis of Magnetic Resonance Imaging (MRI))1932: Operation of first cyclotron , the anti-electron (positron) discovered

Relevance of Fundamental Physics

Early 20th century: Einstein’s insightLight waves consists of packets of energy (photons)

Laws of lasing1960: First laser made to operate - “a solution looking for a problem”

Today’s high bandwidth communication uses laser light signals through optical fibres (last year’s physics Nobel Prize)

Snippets from the Ancestry of Particle PhysicsMatter of our everyday experience is made up of elementary particles

– quarks (up & down) and electrons

1893: JJ Thomson discovers the electron1947: First semiconductor transistor

Today our world turns using “electronics”

Advances in fundamental science drive advances in technologies that alter the way we live

Neutrinos

LHC May Answer Large Questions

Quarks + leptonsPhotons, gluons, W and Z

Higgs ?Super symmetry ?Extra Dimensions ?

HEP Connections to Cosmology

Can we make DM at the LHC?

Extra Dimensions?Super symmetry?

Unification - Schematic

The Forces are Carried by Particles

Present Higgs Search

After looking at “only” 100 trillion interactions we are beginning to rule out a Higgs boson which has a mass of particular values. We will push onward in 2011 and 2012.

LHC Data in 2010 and 2011Commission CMS by finding all SM particles. Start in the “shallows”.

Limits to Date

Limits are approaching 1 TeV, where SUSY needs to exist if it is to stabilize the Higgs mass.

100 Standard Model Forces and Gravity, Running Coupling Constants

M(GeV)

Forcestrength

energy

GUTSUSY

gravity

The Forces in the Standard Model

All force carriers, photon, gluons, gravitons are massless EXCEPT the weak force carriers – why is that? The LHC was designed to find the answer.

The LHC is a Big Step in Quark/Gluon Energy

At the interesting TeV mass scale the reaction rate is a factor at least 1000 x greater at the LHC than at the Tevatron, all else being equal. Truly, the LHC is a machine for discovery, aimed at the TeV mass.

Mass Scale

100,000

LHC at CERN in Geneva

A proton – proton collider, 27 km in circumference. Beams of 7 + 7 TeV protons colliding 40 million times per second

100m underground

W,Z Data – Tie in to Tevatron

All force carriers, g, γ, W and Z were quickly commissioned in CMS in 2010

Top Cross Section

Note the rapid rise from Tevatron to LHC by a factor ~ 20. The LHC is therefore a “top factory” and precision top measurements become possible at the LHC.

Dark Energy and Higgs v.e.v.

2 5 2 3

3 / 8 1.05 10 ( / )

~ 5.6 /

2 10 *

~~ 0.0024

~ 174 , ~ 10

H G x h GeV cm

c x GeV cm

GeV ratio

The measured dark energy is consistent with a vacuum field or a “cosmological term” in General Relativity of 2.4 meV. In contrast the Higgs v.e.v. is 174 GeV which is a spectacular mismatch. Clearly, we do not understand the “vacuum”. Therefore, focus on dark matter for now in HEP.

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