Post on 07-Jan-2016
description
The Shadow of Dark MatterThe Shadow of Dark Matter
Kris Sigurdson
Institute for Advanced Study
Hubble Symposium 2007
Space Telescope Science Institute
April 2, 2007
Kris Sigurdson
Institute for Advanced Study
Hubble Symposium 2007
Space Telescope Science Institute
April 2, 2007
OverviewOverview
• Motivation
• Dark Matter is ‘Dark’
• The Model
• Constraints
• An Observable Effect?
• Particle Physics Setups
• Conclusions
• Motivation
• Dark Matter is ‘Dark’
• The Model
• Constraints
• An Observable Effect?
• Particle Physics Setups
• Conclusions
Stefano Profumo and KS: Phys. Rev. D75 023521 (2007)astro-ph/0611129
MotivationMotivation
•
• But… we don’t know much about the physics of dark matter.
• Worth thinking about alternative avenues of discovery.
•
• But… we don’t know much about the physics of dark matter.
• Worth thinking about alternative avenues of discovery.
Dark Matter
‘Dark’ Matter is Dark Matter ‘Dark’ Matter is Dark Matter
Dark Matter
Not Dark Matter
Dark Matter
Photos: Martin White’s Webpage
‘Dark’ Matter is Dark Matter ‘Dark’ Matter is Dark Matter
Dark Matter
Not Dark Matter
Dark Matter
?
‘Dark’ Matter is Dark Matter ‘Dark’ Matter is Dark Matter
• Very weak coupling to photons
• Strong Limits: Charge (e.g. A. Gould et al. 1990)
Milli-Charge (e.g. S. Davidson et al. 2000; S. Dubovsky et al. 2004)
Magnetic/Electric Dipole (e.g. KS et al. 2004)
• Can NOT appreciably scatter light because the coupling is so very weak
• Very weak coupling to photons
• Strong Limits: Charge (e.g. A. Gould et al. 1990)
Milli-Charge (e.g. S. Davidson et al. 2000; S. Dubovsky et al. 2004)
Magnetic/Electric Dipole (e.g. KS et al. 2004)
• Can NOT appreciably scatter light because the coupling is so very weak
S. Profumo CALTECH
Can Dark Matter Cast a Shadow?
Photon Source Dark Matter Observer
?
The ModelThe Model
• Stable Neutral Dark Matter Particle
• Unstable Neutral Heavier Particle
• Coupled to Photons and each other via a Transition Magnetic/Electric Moment
• Stable Neutral Dark Matter Particle
• Unstable Neutral Heavier Particle
• Coupled to Photons and each other via a Transition Magnetic/Electric Moment
The ModelThe Model
“Atom-like interaction”
The Model: Resonant ScatteringThe Model: Resonant Scattering
Resonant Photon ScatteringResonant Photon Scattering
Relativistic Breit-Wigner Cross Section
CM Energy SquaredCM Momentum
S. Profumo CALTECH
Can Dark Matter Cast a Shadow?
Photon Source Dark Matter Observer
?
The ParametersThe Parameters
€
m1 (DM particle mass)
m2
M (mass scale of effective dipole moment)
€
R ≡ m1 /m2
m2
η ≡ m2 / M
Constraints Constraints
• The coupling can allow forproduction of pairs
• Existing astrophysical constraints on Milli-charge(fractional charge) particles (e.g. G. Raffelt 1996)
• Apply, but replace with:
• The coupling can allow forproduction of pairs
• Existing astrophysical constraints on Milli-charge(fractional charge) particles (e.g. G. Raffelt 1996)
• Apply, but replace with:
Lyman-Lyman-
• But…. constraints from the Lyman-forest on warm dark matter impose:
• This supercedes the stellar energy loss limit for the relevant region of the parameter space unless the dark matter is produced in a nonstandard way
• But…. constraints from the Lyman-forest on warm dark matter impose:
• This supercedes the stellar energy loss limit for the relevant region of the parameter space unless the dark matter is produced in a nonstandard way
The ConstraintsThe Constraints
SN1987ASN1987A
• Excess production of pairs in
SN1987A • Excess production of pairs in
SN1987A
SN Core Plasma Frequency
Excludes:
(Too Much Energy Loss) (Particles Trapped)
The ConstraintsThe Constraints
Big Bang NucleosynthesisBig Bang Nucleosynthesis
• If thermalized in the early Universe around
BBN and would contribute to the number of light degrees of freedom present during BBN
• If thermalized in the early Universe around
BBN and would contribute to the number of light degrees of freedom present during BBN
Excludes:
The ConstraintsThe Constraints
“Running” of em“Running” of em
• In the standard model the strength of the electromagnetic interaction becomes stronger at higher energies
• In the standard model the strength of the electromagnetic interaction becomes stronger at higher energies
Modifies the Running of up to the Z-pole
Must Have:
The ConstraintsThe Constraints
AcceleratorsAccelerators
The ConstraintsThe Constraints
S. Profumo CALTECH
Can Dark Matter Cast a Shadow?
Photon Source Dark Matter Observer
?
Velocity BroadeningVelocity Broadening
• Dark matter particles live in a halo with a nonzero virial velocity dispersion
• Dark matter particles live in a halo with a nonzero virial velocity dispersion
Maxwell-Boltzmann:
Broadening in DM HalosBroadening in DM Halos
Coma-like
Broadened
The OpacityThe Opacity
In Detail:
DM Surface Density
The Optical Depth
An Absorption Feature?An Absorption Feature?
The dynamics of the scattering process ~ Compton scattering
forward scattering is unlikely: if a photon scatters, it’s lost (scattering=absorption)
The dynamics of the scattering process ~ Compton scattering
forward scattering is unlikely: if a photon scatters, it’s lost (scattering=absorption)
Absorption occurs if ~ 1
Can be large enough?
An Absorption Feature?An Absorption Feature?
• Consider a cluster like the Coma Cluster:Estimate ~ 5x1029 MeV/cm2 for a LOS through cluster center
• Consider a source behind or at the center of the cluster (e.g. a quasar)
• Consider a cluster like the Coma Cluster:Estimate ~ 5x1029 MeV/cm2 for a LOS through cluster center
• Consider a source behind or at the center of the cluster (e.g. a quasar)
Absorption Feature?Absorption Feature?
LOS through Center
Vary Intrinsic Width
Potentially Interesting Targets?Potentially Interesting Targets?
• Perhaps: Active Galactic Nuclei (e.g. Centaurus A or M87). With a “DM spike”.
• Perhaps: Gamma Ray Bursts? With the right LOS.
• Statistical Detection?
• Perhaps: Active Galactic Nuclei (e.g. Centaurus A or M87). With a “DM spike”.
• Perhaps: Gamma Ray Bursts? With the right LOS.
• Statistical Detection?
Summary: The (,m2) Plane
S. Profumo CALTECH
“Viable”Parameter
SpaceRegion
2res 5 mE ≈
“Coma”referencesurfacedensitygiving ~ 1
SummarySummary
For:
Mass Range:
Resonant Energy:
Other observables: Annihilation?Other observables: Annihilation?
• Through the same interaction Dark Matter particles could annihilate to monochromatic photons
• Through the same interaction Dark Matter particles could annihilate to monochromatic photons
Annihilation: FluxAnnihilation: Flux
Expected Flux:
Diffuse Gamma from COMPTEL/EGRET:
Unfortunately: Difficult to detect such a line from the Galactic center. Perhaps: Dwarf galaxies (e.g. Profumo and Kamionkowski 2006)
*Dedicated line search by INTEGRAL-SPI also not sensitive enough (Teegarden and Watanabe 2006)
Supersymmetric Absorption?Supersymmetric Absorption?
• SUSY: Neutralino Dark Matter
• In principle: could construct such a model in a SUSY setup with lightest neutralino and next-to-lightest neutralino
• SUSY: Neutralino Dark Matter
• In principle: could construct such a model in a SUSY setup with lightest neutralino and next-to-lightest neutralino
Too low number density for a detectable signal
Extended MSM?Extended MSM?
• MSM: DM abundance, neutrino masses, baryon asymmetry, potentially inflation
(T. Asaka et al. 2005; M. Shaposhnikov 2006)
• MeV mass dark-matter
• Extending this with the transition-moment interactino could lead to the phenomenology discussed here
• MSM: DM abundance, neutrino masses, baryon asymmetry, potentially inflation
(T. Asaka et al. 2005; M. Shaposhnikov 2006)
• MeV mass dark-matter
• Extending this with the transition-moment interactino could lead to the phenomenology discussed here
The EndThe End
• Dark Matter is ‘Dark’ Matter… but for special energies resonant scattering is possible
• a priori: This could lead to absorption features due to dark matter halos.
• A range of the parameter space remains.
• Perhaps: AGN, GRBs, ????
• Not SUSY. Perhaps MSM-like model.
• Dark Matter is ‘Dark’ Matter… but for special energies resonant scattering is possible
• a priori: This could lead to absorption features due to dark matter halos.
• A range of the parameter space remains.
• Perhaps: AGN, GRBs, ????
• Not SUSY. Perhaps MSM-like model.
Stefano Profumo and KS: Phys. Rev. D75 023521 (2007)astro-ph/0611129