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