Particle Physics at the Energy Frontier

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Particle Physics at the Energy Frontier

• Tevatron?LHC
• The Very Early Universe

Tony Liss
Air Force Institute of Technology
April 10, 2008
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Two Views of the Universe

• High energy physicists study the smallest, most
  fundamental objects and the forces between them.
• Cosmologists study what there is on the largest
  possible scales and try to understand how it got
  that way.

But these two very different approaches address
many of the same questions What is the Universe
made of how does it behave?
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The High-Energy View
The matter around us is made up of quarks and
leptons
Electromagnetic Strong Weak Gravity
And held together by four forces, each with a
force carrier
????
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Unification of the Forces
Higgs Bosons born here
Electric Magnetic Weak Strong
Electromagnetic
Electroweak
?
Very (very)High Energy
Low Energy
High Energy
Theory (Standard Model) works up to here
Part way to Einsteins dream!
And you may notice that gravity isnt in this
picture STRING THEORY???
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Cosmology, Particle Physics, the Universe and All
That
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Successes of Particle Physics Big Bang

• Light elements (H to Li) were made in the early
  universe
• And we can calculate how much!

About 1 He nucleus for every 10 protons (25 by
mass)
Predicted abundance depends on density of
baryons particles made of 3 quarks (like a
proton or a neutron)
astron.berkeley.edu/mwhite/darkmatter/bbn.html
The grey band is where the measured calculated
abundances are.
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But Wait!
Recent cosmological measurements put the density
of the universe here.
Most of the universe is not normal (baryonic)
matter!
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Dark Matter (Not a New Idea)
Speed of stuff out here
Doesnt match luminous matter in here!
Theres DARK MATTER in Galaxies!!
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Dark Matter In Between Galaxies Too!
Motion of a galaxy out here
Doesnt agree with luminous matter in here
Wmatter 0.3 from galactic clusters
The Hydra Galactic Cluster
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Studying the Universe at Accelerators
Accelerate particles to very high energies and
smack them together. EMc2 Make new stuff and
study how it behaves.
Fermi National Accelerator Laboratory
This picture shows a proton and antiproton
colliding to make a pair of top quarks. Top
quarks were discovered 14 years ago at Fermilab
Michael Goodman
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Hadron-Hadron Collisions

• Proton-antiproton (Tevatron) or proton-proton
  (LHC) collisions

Each collision (event) is between the hadron
constituents. What can happen isEVERYTHING
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Cross Sections
The total pp cross section is here at 1011!
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This happens only once in 1010 collisions
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Data Taking (TeVatron)
Protons antiprotons collide at 2.5 MHz
0.25Hz of W/Z production
100 Hz of high ET jets
100 Hz of b-quark production
.0002 Hz of top quark production
?? Hz of new physics
20 Acceptance
Prescale/20 10 Acceptance
1 Acceptance
10 Acceptance
?? Acceptance
20 Analysis Mode
85 to analysis
1 Analysis Mode
40 Analysis Mode
?? Analysis Mode
10-2 Hz for analysis
10-5 Hz for analysis
10-2 Hz for analysis
0.4 Hz for analysis
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The CDF Detector at FNAL
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• The Mass of the Top Quark
• The Mass of the W Boson

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Measuring the Top Mass
There are many subtleties to improve S/B and
resolution, but basically
Measure
for each of the decay objects
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Measuring the Top Mass
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Measuring the W Boson Mass
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A Window on the Higgs!
Experimental bound (LEP)
The result is marginally inconsistent with the
SM SUSY????
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Making Higgs Bosons
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Finding The Higgs
The Higgs couples to mass, so its preferred
decay channel depends on its (unknown) mass. As
if life were not difficult enough
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Looking for Higgs (is hard)
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No Higgsyet
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SUSY
Make SUSY particles at an accelerator

• Every quark, lepton and force carrier has a SUSY
  partner (sparticles).
• Sparticles would be made copiously in the early
  (HOT) universe.
• They all decay away quickly, except for the
  lightest one (neutralino), which cant.
• The dark matter might be made up of neutralinos!!

EMc2 happening here!
www.science.doe.gov/hep/EME2004/03-what-is.html
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Another Reason to Believe in SUSY?

• Einsteins dream of a Unified Field Theory, now
  needs SUSY

No SUSY
SUSY
EM
Strength of force
Strength of force
weak
strong
Energy
Energy
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Searching for SUSY an example
SUSY models come in many different flavors, but
one characteristic of many of them is signatures
with large Missing ET Undetectable particles
whose momentum is unmeasured.
In these diagrams charginos and neutralinos
are produced.
In their subsequent decay, the lightest
neutralino is produced but remains undetected.
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Searching for Charginos Neutralinos
The data
Backgrounds
What the signal would look like (if it were there)
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No SUSY So Far

• Many searches, no sightings

• The hunt continues
• At LHC there is 7x more reach (EMc2) for
  making SUSY particles.
• But maybe SUSY isnt the right model
• We can find it anyway if MltE/c2!

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On to the LHC!
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ATLAS Detector at CERN
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ATLAS is VERY BIG
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ATLAS
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A (simulated) Higgs event in ATLAS
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A Black Hole in ATLAS
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The Universe as We Know It
This is NOT what we thought as recently as 10
years ago!!
Atoms
Dark Matter
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Our fabulously successful Standard Model of
particle physics explains only 4 of the
universe So far
Dark Energy
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Perspective

• Our theories of cosmology and particle physics
  are extremely successful, but leave significant
  open questions.
• As new phenomena are discovered, we adapt the
  theories and test them with experiments
  observations.
• The next ten years of accelerator experiments and
  cosmological measurements are guaranteed to bring
  new insights and new surprises!