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Dark Matter


Big Bang Nucleosynthesis tells us the Dark Matter cannot be baryonic... The present precision data were collected at hadron and electron machines. ... – PowerPoint PPT presentation

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Title: Dark Matter

Dark Matter Dark Energy New Challenges for
Particle Physics
  • Jim Siegrist
  • USF, 29-Apr-04
  • Acknowledgement Murayama, Hinchliffe, Quantum
    Universe Writing Team

What is the nature of the universe and what is it
made of? What are matter, energy, space and
time? How did we get here and where are we going?
Particle Physics and the Quantum Universe
  • Understanding the Universe requires particle
    physics to determine its fundamental nature
  • Astrophysical obs ? parameters of Universe
  • Accelerator expts ? search for quantum
  • Two ends must meet
  • Observing the relics of the big bang
  • Recreating the particles and forces of early
    Universe at accelerators

Particle Physics Has a Complete Understanding of
Ordinary Matter
  • We have a commanding knowledge of the particles
    and forces around us.
  • A theoretical framework called the Standard
    Model (SM) describes data with exquisite

Symmetry Plays the Central Role
  • Formulation of the SM reveals that the laws of
    physics exist because of underlying (global, eg.
    space-time independent) symmetries
  • Translation invariance gt momentum conservation
  • Rotational invariance gt angular momentum
  • Some symmetries have been lost as the Universe
    has cooled from the Big Bang
  • Particle masses arise because the vacuum today
    has different symmetry properties than during the
    initial fireball
  • Space-time dependent (local, or gauge) symmetries
    generate the forces in the SM

The Standard Model Framework indicates how it can
be systematically extended
Recent Discoveries Indicate Particle Physics Has
Reached a Singular Moment
A Revolution in Particle Physics Some of the
Open Issues
  • What is Dark Matter?
  • What is Dark Energy?
  • Are there extra space dimensions?
  • Do all the forces become one?
  • What happened to the anti-matter?
  • How did the Universe come to be?

We know the Standard Model is an incomplete
description of the Universe
Dark Matter
  • Astrophysical Perspective
  • Particle Physics Perspective
  • Models for new physics
  • Current and future work

Astrophysical Perspective Galaxy Rotation
  • Scale 10KPc (30,000 light years)
  • Use Doppler shift of light from star in spiral
    galaxy to give velocity (red shift)
  • Expect velocity to fall off with distance from
  • - …but it doesnt

Dark Matter in Galaxy Clusters
  • Galaxies form clusters bound in a gravitational
  • Hydrogen gas in the well gets heated, emits
  • Can determine baryon fraction of the cluster
  • fBh3/20.056?0.014
  • Combine with the BBN
  • Wmatterh1/20.38?0.07
  • Agrees with other methods

Microlensing Searches
  • Gravitational lensing effect
  • Observed MACHO Event
  • Symmetrical Light Curve and one off
  • Gravitational identical curves at different
    wavelengths (unlike variable stars)

Particle Physics Perspective
  • Big Bang Nucleosynthesis tells us the Dark Matter
    cannot be baryonic…
  • We are forced to introduce something beyond the
    Standard Model framework.

Particle Dark Matter
  • It is not dim small stars (e.g., MACHOs)
  • WIMP (Weakly Interacting Massive Particle)
    strongly favored
  • Stable heavy particle produced in early Universe,
    left-over from near-complete annihilation
  • TeV1012eV the correct mass scale

Cold Thermal Relics
Figure from Kolb
  • Dark Matter fraction increases as M increases
  • Dark Matter fraction increases as ? decreases
  • Interactions must be fully specified before a
    candidate can be ruled out. Calculations are
    therefore limited to those fully specified models.

A Promising Model Supersymmetry(SUSY)
  • Additional symmetries have to be proposed to
    extend the SM to solve the Dark Matter problem
  • One approach is to double the particle spectrum
    by positing a symmetry that links fermions to
    bosons…giving a sparticle paired with each SM
    particle, differing by ½ unit of spin
  • Originally studied for other reasons…

Problems Possibly Solved by Supersymmetry
  • Dark Matter problem the lightest SUSY particle
    is stable gt candidate for Dark Matter
  • Explanation for how mass is generated in the SM
    gt requires a heavy top quark, as was observed
    after the SUSY prediction
  • Introduces a higher level of symmetry that
    stabilizes the theory against higher order
    corrections (solves the hierarchy problem)
  • Provides for Unification of the forces into a
    single force at very high energies
    (alternatively, at very short distances or in the
    very early Universe)

Standard Model and Supersymmetry
Breaking Supersymmetry
i.e. SM particles plus two Higgs doublets and
their SUSY partners
  • How is supersymmetry broken?
  • Supergravity-inspired (mSUGRA)the typical
  • parameters m1/2, m0, A0, tan ?, sign(?)
  • radiative EWSB occurs naturally from large top
  • the ?01 is the LSP
  • ?01, ?02, ??1, sleptons and h are light
  • ?03, ?04, ??2, squarks and gluinos are heavy
  • Many other possibilities have been studied

Opening the Door
  • Once SUSY is introduced,
  • We can get started to discuss physics at shorter
  • It opens the door to the next level
  • Hope to answer great questions
  • The solution to the Dark Matter problem itself,
    e.g., SUSY, provides additional probe to how the
    Universe works.

SUSY and Dark Matter
  • Most SUSY models have unbroken R-parity that
    guarantees that lightest sparticle (LSP) is
  • LSP must be neutral candidates are B W0 H ? and
  • ? is strongly disfavored by LEP and direct
  • Parameters m1/2 (gaugino masses), m0 (squark
    masses), tan ?, sign(?), A, specified at GUT
    scale, fully describes model.
  • LSP is usually B and mass controlled by m1/2

SUGRA Allowed Regions
Plots are usually shown for fixed tan ß sign (µ),
A as a region in m1/2 m0 space.
Low mass region m1/2 and m0 are small
0.1 ? ?h2 ? 0.3
After WMAP Results
Recall for LHC that roughly mg 2.4m1/2 and
me 1.1m0

LSP forced to lower masses by WMAP results good
for accelerator based searches.
Current and Future Experimental Work
  • Today Tevatron
  • Soon Large Hadron Collider
  • Tomorrow Linear Collider

SUSY higgs A/H in ??, bb
Run II 5? discovery M175 GeV for tan?50 with 5
bb (h/H/A) enhanced at large tan? A ? bb, so 4
bs in final state A ? ??, Run I analysis 4
jets, 3 b tags
  • Work in progress
  • Higgs multijet trigger studies
  • 4 jets QCD background
  • B-mistag studies for background

Control sample requires two b-tags Data and MC
agree very well
Next Steps LHC in 2007
The LHC detectors are designed to find the SM
Higgs. Low mass is covered by ??, ttH(bb),
qqH(WW,??). A low mass Higgs has many
accessible decay modes ? some couplings measured.
ATLAS Detector at CERNs Large Hadron Collider
Inner Tracking Detector
ATLAS Overview
  • Production is complete or in progress for most
    ATLAS components.
  • Underground installation has been underway for
    some months.
  • The schedule continues to be tight, but it is
    feasible for ATLAS to be ready for first LHC beam
    as planned in 2007.

LHCs Task
  • Find the particle(s) responsible for mass
  • Could be Higgs, many Higgss, SUSY, Extra
  • Power of LHC is its enormous mass reach relative
    to current facilities.
  • Even low luminosity will open a new window.
  • 10pb -1 (1 day at 1/100 of design luminosity)
    gives 8000 t?t and 100 QCD jets beyond the
    kinematic limit of the Tevatron
  • If SUSY is correct, it could be found with 100pb

How fast can SUSY be found at LHC?
The LHC should be able to establish the existence
of SUSY and open many avenues to study masses and
decays of SUSY partices, if m(SUSY) is less than
a few TeV. For example in the SUGRA model, the
cosmologically interesting region of the SUSY
search will be covered in the first weeks of LHC
running, and the 1.5 to 2 TeV mass range for
squarks and gluons will be covered within one
year at low luminosity.
The Linear Collider
  • Full exploration of SUSY requires the CERN LHC
  • A proton-proton collider with an energy seven
    times that of the Tevatron.
  • Together with a high-energy ee- linear collider.
  • The LHC and a linear collider are both necessary
    to discover and understand the new physics at the
    TeV scale.
  • A coherent approach, exploiting the strengths of
    both machines, will maximize the scientific
    contributions of each.

Why Both a Hadron and Electron Collider? Precision
The present precision data were collected at
hadron and electron machines. The two probes
provide complementary views much like infrared
and ultraviolet astronomy complement the optical.
We fully expect this theme to continue into the
How Will a 500 GeV Linear Collider Complement the
  • Experiments at the LHC are likely to discover
    Dark Matter
  • But a linear collider answers crucial questions
  • What is the spin state of the candidate?
  • Does it have the coupling consistent with Dark
    Matter particles?
  • Is it produced in a manner consistent with
    production of relics in the early Universe?

A fully International Project planned for the
next decade
Dark Energy
  • Astrophysical Perspective
  • Particle Physics Perspective
  • Models and Ideas
  • Current and Future Work (for Supernovae)

Type-IA Supernovae
As bright as the host galaxy
Type-IA Supernovae
  • Type-IA Supernovae standard candles
  • Brightness not quite standard, but correlated
    with the duration of the brightness curve
  • Apparent brightness
  • ? how far (time)
  • Know redshift
  • ? expansion since then

What makes the supernova measurment special?
An exhaustive accounting of sources of SN
systematic uncertainities
  • SN Ia Evolution
  • shifting distribution of progenitor
  • shifting distribution of SN physics params
  • amount of Nickel fused in explosion
  • distribution of Nickel
  • kinetic energy of explosion
  • opacity of atmospheres inner layers
  • metallicity
  • Gravitational Lensing (de)amplification
  • Dust/Extinction
  • dust that reddens
  • evolving gray dust
  • clumpy
  • homogeneous
  • Galactic extinction model
  • Observational biases
  • Malmquist bias differences
  • non-SN Ia contamination
  • K-correction uncertainty
  • color zero-point calibration

Type-IA Supernovae
  • Clear indication for cosmological constant
  • Can in principle be something else with negative
  • With wp/r,
  • Generically called Dark Energy

Cosmic Concordance
  • CMBR flat Universe
  • W1
  • Cluster data etc
  • Wmatter0.3
  • SNIA
  • (WL2Wmatter)0.1
  • Good concordance among three

Constraint on Dark Energy
  • Dark Energy is an energy that doesnt thin much
    as the Universe expands!
  • Need negative pressure
  • Data consistent with cosmological constant

Cosmic Coincidence Problem
  • Why do we see matter and cosmological constant
    almost equal in amount?
  • Why Now problem
  • Actually a triple coincidence problem including
    the radiation
  • If there is a fundamental reason for
    rL((TeV)2/MPl)4, coincidence natural

Arkani-Hamed, Hall, Kolda, HM
Embarrassment with Dark Energy for Particle
  • A naïve estimate of the cosmological constant in
    Quantum Field Theory rLMPl410120 times
  • The worst prediction in theoretical physics!
  • People had argued that there must be some
    mechanism to set it zero
  • But now it seems finite???

Many ad-hoc Models to Explain Dark Energy
Current and Future Work
  • Nearby Supernova Factory/ SCP
  • SNAP
  • Some thoughts

Understanding Supernovae
Nearby Supernova Factory well in progress,
refining understanding Supernova Cosmology
Project 2003 Results Higher redshifts,
Greatly improved systematics checks Ground
based searches continuing Refining
understanding (cf. CMAGIC ?m0.08) Probing
averaged DE equation of state w Important,
but will reach ground systematics limit
--cant achieve robust w? --confusion limit
in interpreting nature of DE
Nearby SN Factory follow-up Instrument
SNAP/JDEM The Next Generation
  • Supernova/Acceleration Probe
  • Dedicated exploration of dark energy w(z)
  • Maps expansion history a(t)
  • Reveals dark matter thru gravitational lensing

SNAP/JDEM The Next Generation
  • SNAP is wide, deep, and colorful
  • Essential to control systematics
  • Realized by LBNL technology CCDs

SNAP focal plane array
SNAP Fundamental Physics
  • Space allows high z and systematics control
  • w(z) ? V / V(?)
  • High energy physics, extra dimensions, new
    gravity, inflation redux?

How can we solve the mystery of dark energy?
  • A Dark Energy fills the vacuum of empty space
  • Accelerating expansion of Universe
  • Dark energy needs a quantum explanation
  • The Higgs field fills the vacuum of empty space
  • Gives particles mass
  • Are dark energy and the Higgs related?
  • SUSY a natural context for both

LHC, SNAP/JDEM and LC are crucial tools for
Cosmology and Particle Physics meet at TeV scale
  • Dark Matter
  • Fermi (Higgs) scale
  • v250GeV
  • Dark Energy
  • rL(2meV)4 vs (TeV)2/MPl0.5meV
  • Neutrino
  • (Dm2LMA)1/27meV vs (TeV)2/MPl0.5meV
  • TeV-scale physics will be rich

  • Answers to origins of Dark Matter and Dark Energy
  • Many exciting possibilities
  • One of several thrusts in particle physics today

Expect a 21st Century Revolution in Particle
  • Books
  • The Elegant Universe, B. Greene, Random House,
  • Supersymmetry, G. Kane, Perseus Publishing, 2000
  • Quarks, Leptons and the Big Bang, J. Allday, IOP,
  • Facts and Mysteries in Particle Physics, M.
    Veltman, World Scientific, 2003.
  • The Fabric of the Cosmos, B. Greene, Knopf, 2004.
  • Connecting Quarks with the Cosmos, National
    Academy Press, 2003
  • Articles
  • Papers in the Scientific American special report
    on the cosmos (February 2004)
  • The Cosmic Symphony, Wayne Hu and Martin White
    (p. 44)
  • Reading the Blueprints of Creation, Michael A.
    Strauss (p.54)
  • From Slowdown to Speedup, Adam Riess and
    Michael S. Turner (p. 62)
  • Out of the Darkness, George Dvali (p. 68)
  • Web sites
  • http//www.ostp.gov/ (see OSTP NEWS, Physics of
    the Universe Report)
  • http//www.interactions.org
  • http//www.interactions.org/pdf/Quantum_Universe.p
  • Experiments
  • ATLAS http//atlas.web.cern.ch/Atlas/Welcome.html

  • Papers
  • 1 H. Baer, C. Balazs and A. Belyaev,
    Neutralino relic density I minimal supergravity
    with co-annihilations, JHEP 0203 (2002) 042
  • 2 D. N. Spergel et al., First Year Wilkinson
    Microwave Anisotropy Probe (WMAP) Observations
    Determination of Cosmological Parameters,
  • 3 J. R. Ellis, K. A. Olive, Y. Santoso and V.
    C. Spanos, Supersymmetric dark matter in light
    of WMAP, arXivhep-ph/0303043.
  • 4 L. Roszkowski, R. Ruiz de Austri and T.
    Nihei, New cosmological and experimental
    constraints on the CMSSM, JHEP 0108 (2001) 024
  • 5 V. Bertin, E. Nezri and J. Orloff,
    Neutralino dark matter beyond CMSSM
    universality, JHEP 0302 (2003) 046
  • 6 U. Chattopadhyay, A. Corsetti and P. Nath,
  • 7 P. Gondolo, J. Edsjo, P. Ullio, L.
    Bergstron, M. Schelke and E. A. Baltz, DarkSUSY
    A numerical package for supersymmetric dark
    matter calculations, arXivastro-ph/0211238.
  • 8 K. A. Olive, TASI lectures on dark
    matter, arXivastro-ph/0301505.
  • 9 J. L. Feng, K. T. matchev and T. Moroi,
    Phys. Rev. D 61 (2000) 075005.
  • 10 M. Fujii and T. Yanagida, Phys. Rev. D 66
    (2002) 123515 arXivhep-ph/0207339.
  • 11 A. de Gouvea, T. Moroi and H. Murayama,
    Phys. Rev. D 56 (1997) 1281.
  • 12 T. Moroi and L. Randall, Nucl. Phys. B 570
    (2000) 455.
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