THE CONVERGENCE OF PARTICLE PHYSICS AND ASTROPHYSICS: THE LHC/FERMI ERA

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THE CONVERGENCE OF PARTICLE PHYSICS AND
ASTROPHYSICS THE LHC/FERMI ERA

• Public Lecture at the International Workshop on
  Particle Physics and Cosmology, University of
  Oklahoma, Norman 2009

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Einstein spoke of the incomprehensible
comprehensibility of nature. Consciously or
not, this viewpoint drives much of what we do in
science, especially in astronomy, astrophysics
and particle physics. When we see surprising or
interesting features in nature, we believe we
should be able, over time, to understand them.
This view has historical support.
LHC/Fermi-GLAST two instruments to extend our
understanding.
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Aerial view of LHC
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Muon Toroids
Muon superconducting Toroids in the ATLAS
Detector at the LHC
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GLAST (Fermi) launch, June
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What are we hoping to learn with these
instruments?

• Convergence of particle physics, astrophysics
  and cosmology
• What are the basic laws of nature an ingredient
  in any study of the universe (compare nuclear
  physics, stars)?
• What is the composition of the universe?
• How did the universe get to be as it is?

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Particle physicists, in the past few decades,
have determined completely the laws of nature
which govern phenomena on scales as small as
10-17 cm. Embodied in the Standard Model, which
describes the strong nuclear force, the weak
nuclear force, and electromagnetism (light,
electricity, magnetism) This model has been
subjected to stringent tests.
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PDG Wall Chart
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Previous generation of instruments Stanford
Linear Accelerator
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Quarks were discovered at SLAC
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Later, precision studies of quarks, leptons, W,
Z, gluons at CERN, SLAC, Fermilab

1. CERN (Geneva, site of LHC) LEP collided
   electrons, positrons. Precision studies of the
   weak interactions. In same tunnel as LHC
2. SLAC SLAC Linear collider, new technology,
   beams smaller than human hair collided with
   enormous energies. Similar studies.
3. Fermilab collide protons, antiprotons at very
   high energies. Precision studies of the strong
   interactions.

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CDF DØ data taking e 90
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By 1995, the strong and weak interactions were
understood and tested with high precision.
Closely parallel to the triumph of Quantum
Electrodynamics, associated with Feynman,
Schwinger, Tomanaga, Lamb. No interesting
discrepancies.
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• Puzzles with this picture
• Many fundamental constants masses of quarks
  and leptons, strength of the interactions (17 in
  all). Shouldnt it be possible to understand
  these?
• Einsteins General Theory of Relativity is not
  compatible with this structure, but we know that
  this describes gravitation in the universe very
  well.
• Related to (2), we dont understand why gravity
  is so weak.
• Some of the constants in (1) are very surprising.
  E.g. there is one called µ, which is just a pure
  number, but µ lt 10-9

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• Possible solutions (much more about these
  shortly)
• For the puzzle of the weakness of gravity, a
  hypothetical new symmetry of nature, called
  supersymmetry. Turns out to also explain some of
  the constants the strength of the strong
  interactions related to the strength of the
  electromagnetic and weak interactions.
• For the puzzle of quantum gravity, string theory.
• For the question of µ, a hypothetical particle
  called the axion (subject of searches at
  Livermore)
• For the puzzle of the many constants, string
  theory again.

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• Meanwhile, over the same period, astronomers and
  astrophysicists established
• The big bang really happened. The universe (at
  least what we can hope to see of it) is 15
  billion years old its history is well understood
  from three minutes until the present. We have
  some evidence of phenomena at much earlier times
  (10-25 sec after the big bang).
• The universe consists of about 5 baryons
  (protons and neutrons), 25 dark matter, 70 dark
  energy.

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Detailed study of the CMBR

• From satellites and earth based (balloon)
  experiments. Most recently the WMAP satellite.

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Detailed information about the universe
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• Questions
• What is the dark matter?
• What is the dark energy?
• Why is there matter at all?
• What happened at the very early stages of the big
  bang (something called inflation, but what is
  it?)
• What came before?

None of these questions can be answered within
our present knowledge of the laws of nature!
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All of our cosmic questions are tied to the
questions from particle physics
Supersymmetry ! Dark Matter
Supersymmetry ! Baryons
Axions ! Dark Matter
String theory ! Possible explanation of inflation
String theory ! Possible explanation of dark
energy
String theory ! May explain what came before
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Magnet Pictures
2 in 1 superconducting dipole magnet
being installed in the CERN tunnel
LHC dipoles waiting to be installed.
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Detecting Particle Collisions
When high energy particles collide, they produce
many more particles.
Simulation of an event in ATLAS detector. White
lines are the four muons. The other tracks are
due to particles from quarks in the protons.
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ATLAS Detector
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Tracker Pictures
Tracker
Inserting silicon detector into tracker
Inserting solenoid into calorimeter
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Calorimeter Installation
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Muon Toroids
Muon superconducting toroids.
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Endcap muon sector
Endcap Muon Sectors
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SCALE OF THE PROJECT

• The stored energy in the beams is equivalent
  roughly to the kinetic energy of an aircraft
  carrier at 10 knots (stored in magnets about 16
  times larger)
• There will be about a billion collisions per
  second in each detector.
• The detectors will record and stores only
  around 100 collisions per second.
• The total amount of data to be stored will be 15
  petabytes (15 million gigabytes) a year.
• It would take a stack of CDs 20Km tall per year
  to store this much data.

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• Collide two protons each with energy 7TeV.
• (1TeV is roughly the kinetic energy of a flying
  mosquito. This energy is squeezed into a region
  10-12 of a mosquito.)

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LHC Accident Fall 2008
Electrical failure at a magnet junction damage
to several magnets, large release of helium
design flaws exposed, currently being assessed.
Delay of a few to many months possible, situation
should be clearer this week.
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Information on the machine status is available on
the web
cern_lhc_page.htm http//lhc.web.cern.ch/lhc/
LHC Commissioning - home.htm http//lhc-commission
ing.web.cern.ch/lhc-commissioning/
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Update from the DG (edited)
Subject     LHC Performance Workshop, Chamonix
2009 - Message from the Director-General -
Message du Directeur général Date     Fri, 6
Feb 2009 191741 0100 From     Rolf Heuer
ltrolf.heuer_at_cern.chgt To     cern-personnel
ltcern-personnel_at_cern.chgt Many issues were
tackled in Chamonix this week, and important
recommendations made. Under a proposal submitted
to CERN management, we will have physics data in
late 2009, and there is a strong recommendation
to run the LHC through the winter and on to
autumn 2010 until we have substantial quantities
of data for the experiments. With this change to
the schedule, our goal for the LHC's first
running period is an integrated luminosity of
more than 200 pb-1 operating at 5 TeV per beam,
sufficient for the first new physics measurements
to be made. This, I believe, is the best possible
scenario for the LHC and for particle physics.
Since the incident, enormous progress has been
made in developing techniques to detect any small
anomaly. These will be used in order to get a
complete picture of the resistance in the splices
of all magnets installed in the machine. This
will allow improved early warning of any
additional suspicious splices during operation.
The early warning systems will be in place and
fully tested before restarting the LHC.
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What Might the LHC Discover?
The short answer we don t know! But there are
plenty of speculations, motivated by the
questions on our lists. We cant review them
all, and it is likely that none of our guesses
are right. But, as a prototype, well consider
the most popular one Supersymmetry.
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... doubled particle spectrum ... ?
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Why supersymmetry (maybe?)

• Higgs field very heavy, mass gt 116 GeV (more
  than 100 times mp). Cant be too much more.
• Real question why so light?
• Dimensional analysis mH ¼ Mp 1018 GeV.
• In quantum field theory, there really are
  contributions to the Higgs mass which are this
  large unless either
• The Higgs particle is a composite, with a size a
  ¼ 1/mH,
• Nature is supersymmetric

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Why Supersymmetry Solves this Hierarchy Problem
Lorentz Model for electron as a blob of charge
of size r. Ecoul e2/r
Einstein Energy mass c2 me e2/r c2
But we know r lt 10-17 cm me gt 10 ¼ 10
mp! Dirac theory of electron fixes this
(Weisskopf) roughly speaking the positrons
cancel off the big contribution of the Coulomb
field.
In supersymmetry, the extra particles cancel the
big contributions to the Higgs particles if their
masses are not too different than mH.
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If supersymmetry is there, LHC will find it!
(Fermilab has looked and will continue)
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Discovery of Supersymmetry is Likely to Answer
Several Questions in Our Lists

1. Explain why gravity is weak (mH Mp)
2. Supersymmetry -- (almost) for free explains
   the value of the strong coupling in terms of the
   couplings of weak interactions and
   electromagnetism.
3. Supersymmetric theories for free almost
   always possess a candidate for the dark matter, a
   WIMP (weakly interacting massive particle).
4. Supersymmetry can readily explain the excess of
   matter over antimatter.

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If supersymmetry accounts for the dark matter, we
ought to be able to find it

1. Search in mines for (rare) collisions of dark
   matter particles with ordinary particles.cdms.html
   http//astro.fnal.gov/projects/cdms.html
2. Dark matter particles might annihilate frequently
   near the galactic center see energetic
   particles in Fermi/GLAST.

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FERMI-GLAST
If dark matter particles are from supersymmetry,
they will sometimes meet and annihilate in areas
where they are most dense the products of these
annihilations can be seen by GLAST, other
instruments. Already some tantalizing evidence
(esp. from an Italian satellite, PAMELA) for such
phenomena.
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Being greedy, physicists speculate about the
other questions on the list. The structure with
the potential to address all of them Sting
Theory

• A contentious subject.
• What has it explained?
• When will it be tested?

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String Theory

• For reasons that are still not understood,
  assuming that the fundamental entities are
  strings rather than point particles automatically
  gives a sensible quantum theory of gravity
  (General Relativity).
• At the same time, these theories automatically
  give structures which look remarkably like the
  Standard Model.

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As so often, the issues are exaggerated and
misrepresented by the antagonists.
But trust me I speak with authority (I hang out
with string theorists and I went to high school
with Smolin)

• String theory has taught us that quantum
  mechanics and gravity can get along something
  not widely believed before (e.g. Hawking).
  Smolin is wrong when he says he has an
  alternative which accomplishes this, but this is
  not really so important.

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• What theorists have studied string theory and
  related objects are definitely unrealistic
  models. They have the right to believe that more
  realistic theories exist and to speculate on
  their properties, but at the moment they are
  groping. Only some inklings of the underlying
  structure.

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Could the LHC discover string theory?
Maybe. String theory may predict supersymmetry,
the spectrum (masses) of the new particles. It
might predict (a real long shot, but terribly
exciting if true) extra dimensions of space which
could be observed, black holes
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So now we wait and see. Theorists,
experimentalists, working hard to be ready to
interpret the data as it starts to come in,
hopefully within less than a year!
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Extra Slides
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The size of the LHC
In a magnetic field B, a particle of charge q and
momentum p travels in a circle of radius R given
by
At the LHC, the desired beam energy 7 TeV and
the state of the art dipole magnets have a field
of 8 Tesla. Plugging in and converting units
gives a radius of 3 km and a circumference of 18
km.