What Are They Doing at Fermilab Lately?

Don Lincoln

Fermilab

What’s the Point?High Energy Particle Physics is a study of the smallest pieces of matter.

It investigates (among other things) the nature of the universe immediately after the Big Bang.

It also explores physics at temperatures not common for the past 15 billion years (or so).

It’s a lot of fun.

Periodic Table

All atoms are madeof protons, neutronsand electrons

Helium Neon

u

du u

d d

Proton NeutronElectron

Gluons hold quarks togetherPhotons hold atoms together

• All particles have ‘anti-particles’, which have similar properties, but opposite electrical charge

Particles– u,c,t +2/3– d,s,b -1/3– e,, -1

Anti-particles– u,c,t -2/3– d,s,b +1/3– e,, +1

Now (15 billion years)

Stars form (1 billion years)

Atoms form (300,000 years)

Nuclei form (180 seconds)

Protons and neutrons form (10-10 seconds)

Quarks differentiate (10-34 seconds?)

??? (Before that)

Fermilab4×10-12 seconds

LHC10-13 Seconds

Fermi National Accelerator Laboratory(a.k.a. Fermilab)

• Begun in 1968

• First beam 1972 (200, then 400 GeV)

• Upgrade 1983 (900 GeV)

• Upgrade 2001 (950 GeV)

Jargon alert: 1 Giga Electron Volt (GeV) is 100,000 times more energy than the particle beam in your TV.

If you made a beam the hard way,it would take 1,000,000,000 batteries

Fermilab Facts• Named after Enrico Fermi, the famous Italian physicist

who worked on the Manhattan Project.

• Current Director: Michael S. Witherell

• Fermilab encompasses 6800 acres, much of it used for prairie restoration and preserving open space in the western suburbs.

• Employees about 2000 people.

• Original cost $250,000,000. Approximately the same amount in upgrades over the last 30 years.

• Electric bill between $10,000,000 and $20,000,000

• NO classified work is done here, ask all the questions and take all the pictures you want.

Fermilab’s Wilson Hall

Saint-Pierre Cathedral in Beauvais, France1272 A.D.

Why the Buffalo?

• Radiation Detector?

• Nah...that’s why we have graduate students....and they’re cheaper....

Increasing ‘Violence’ of Collision

ExpectedNumber

ofEvents

Run II

Run I

Increased reach for discovery physicsat highest masses

Huge statistics for precision physicsat low mass scales

Formerly rare processesbecome high statisticsprocesses

1

10

100

1000

The Main Injector upgrade was completed in 1999.

The new accelerator increases the number of possible collisions per second by 10-20.

DØ and CDF have undertaken massive upgrades to utilize the increased collision rate.

Run II began March 2001

How Do You Detect Collisions?

• Use one of two large multi-purpose particle detectors at Fermilab (DØ and CDF).

• They’re designed to record collisions of protons colliding with antiprotons at nearly the speed of light.

• They’re basically cameras.

• They let us look back in time.

DØ Detector: Run II

30’

30’

50’

• Weighs 5000 tons• Can inspect 3,000,000

collisions/second• Will record 50

collisions/second• Records

approximately 10,000,000 bytes/second

• Will record 1015 (1,000,000,000,000,000) bytes in the next run (1 PetaByte).

Remarkable Photos

This collision is the most violentever recorded. It required thatparticles hit within 10-19 m or 1/10,000 the size of a proton

In this collision, a top and anti-top quark were created,helping establish their existence

Highlights from 1992-1996 Run

• Limits set on the maximum size of quarks (it’s gotta be smaller than 1/1000 the size of a proton)

• Supported evidence that Standard Model works rather well (didn’t see anything too weird)

• Studied quark scattering, b quarks, W bosons

• Top quark discovery 1995

The Needle in the Haystack: Run I• There are 2,000,000,000,000,000 possible

collisions per second.

• There are 300,000 actual collisions per second, each of them scanned.

• We write 4 per second to tape.

• For each top quark making collision, there are 10,000,000,000 other types of collisions.

• Even though we are very picky about the collisions we record, we have 65,000,000 on tape.

• Only 500 are top quark events.

• We’ve identified 50 top quark events and expect 50 more which look like top, but aren’t.

Run II

×10

Top Quark Run I: The Summary• The top quark was discovered in 1995• Mass known to 3% (the most accurately known

quark mass) • The mass of one top quark is 175 times as heavy

as a proton (which contains three quarks)

Why??

?

In 1964, Peter Higgs postulated a physics mechanism which gives all particles their mass.

This mechanism is a field which permeates the universe.

If this postulate is correct, then one of the signatures is a particle (called the Higgs Particle). Fermilab’s Leon Lederman co-authored a book on the subject called The God Particle.

top

bottom

Undiscovered!

“LEP observes significant Higgscandidates for a mass of 115 GeVwith a statistical significance of 2.7 and compatible with theexpected rate and distribution ofsearch channels.”

Chris Tully, Fermilab Colloquium13-Dec-2000

Non-Expert Translation:

Maybe we see something, maybe we don’t.

What we see is consistent with being a Higgs Particle. But it could end up being nothing.

It’s Fermilab’s turn.

Calorimeters Tracker

Muon System

Beamline Shielding

Electronics

protons antiprotons

66 feet

In Run II (March 1, 2001), the FermilabTevatron will deliver 10-20 times asmany collisions per second as Run I.

The DØ detector required an overhaulin order to cope.

Eight cylinders covered withscintillating fiberare read out with a novel light detector (VLPCs).

VLPCs

DØ Fiber Tracker

See the Display!

1.25 mp

p

DØ Silicon Tracker

• 800,000 distinct detector elements

• Very complex (fragile)• Absolutely crucial for viewing

the details of how particles behave near the collision.

• Particles that don’t come from the collision point serve as ‘flags’ of interesting physics.

DØ Muon System

• Muons provide a signature of many interesting physics events.

• Muons penetrate dense material for long distances.

• Thus muon detectors are outside the large amount of metal that makes the rest of the detector.

• The muon system consists of many different detector technologies, and is the physically largest system.

Data-Model Comparison

Data-Model Comparison

Run II: What are we going to find?

I don’t know!

Improve top quark mass and measure decay modes.

Do Run I more accurately

Supersymmetry, Higgs, Technicolor, particles smaller than quarks, something unexpected?

Why DØ? Ask famous Hollywood Star

And it stuck.......

Why DØ? The Real Reason

AØ: The High Rise

BØ: The Competition

CØ: Future BTeV

FØ: The RF

EØ: This Space For Rent

DØ: Fermilab’s Best Detector

DØ vs. Borg

Coincidence? Or just another cool thing about DØ?

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