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Stefano Profumo. UC Santa Cruz Santa Cruz Institute for Particle Physics T.A.S.C. [Theoretical Astrophysics in Santa Cruz]. New Physics with ACTs in the Fermi Era. TeV Particle Astrophysics 2009 SLAC National Accelerator Laboratory, Menlo Park, CA, July 13-17, 2009.

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Stefano Profumo

UC Santa Cruz

Santa Cruz Institute for Particle Physics

T.A.S.C. [Theoretical Astrophysics in Santa Cruz]

New Physics with ACTs

in the Fermi Era

TeV Particle Astrophysics 2009

SLAC National Accelerator Laboratory, Menlo Park, CA,

July 13-17, 2009


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Annihilation debris: an unavoidable

consequence of thermal WIMPs

Gamma Rays

1. “Primary”

  • Hadronization, p0 gg

  • Final State Radition (e.g. L+L- g)

  • (included in e.g. DMFIT)

  • “Intermediate State” Radiation

  • (model-dependent, incl. in DSv5)

  • Loop-suppressed radiative

  • annihilation modes (gg, Zg, hg, …)

Credit: Fermilab Website


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3. Compute the Signals

(IC off CMB/starlight, Synchrotron emission,…)

WIMP annihilation also produces stable Electrons and Positrons,

which diffuse and loose energy

Inverse Comptonoff CMB and starlight photons,

Bremsstrahlungand Synchrotronemission

produce radiation from radio to gamma-ray frequencies

1. Source Term

2. Transport Equation


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Annihilation debris: an unavoidable

consequence of thermal WIMPs

Gamma Rays

1. “Primary”

2. “Secondary”

  • Inverse Compton (e+ge+g)

  • (where g from CMB, starlight, IRB…)

  • Bremsstrahlung

  • Synchrotron (for large enough B)

Credit: Fermilab Website


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The multi-wavelength spectrum expected from a

41 GeV “bino” annihilating in the Coma cluster

Set by the

DM particle

mass scale

“Environment”-dependent

(B, gas density, diffusion)

Colafrancesco, Profumo and Ullio (2005)


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What is “magic” about gamma-ray telescopes

for the search for dark matter?

s ~ m2/mZ4

W ~ 1/s ~ m-2

W~m

s ~ m-2

W ~ m2

They probe the energy range where

the thermal cold DM mass scale is

Baltz (2004)


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What is “magic” about gamma-ray telescopes

for the search for dark matter?

Gamma-Ray

“Debris”

WIMP Mass

Range

Secondary & Low-E

Primary Radiation

Non-thermal

Production


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What is “magic” about gamma-ray telescopes

for the search for dark matter?

an “old”

Morselli plot

WIMP Mass

Range

Secondary & Low-E

Primary Radiation

Non-thermal

Production


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Role of ACT’s in

the multi-frequency

siege to dark matter

in the Fermi Era

4. Cosmic Ray

Electrons/

Positrons

1. Dwarf

Galaxies

2. Galaxy

Clusters

3. Galactic

Center


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Solar Array ACT located

at Solar Two,

Daggett (CA), operated by

UC Davis in ’04-’05

Observed PSR/SNR

(Crab, Geminga),

AGN (Mk421, 501)

and dSph Draco

Reported GR excess from Draco, later attributed to

problems with noise assisted trigger threshold connected to starlight

dSph are DM dominated and GR-quiet objects:

the usual suspect, DM interpretation of the excess

L.Bergstrom & D.Hooper, hep-ph/0512317 and S.Profumo & M.Kamionkowski, astro-ph/0601249


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Excess Counts !!!

An important lesson: dSph are ideal targets for indirect DM searches

Moreover: ACTs are complementary to satellite-based GR telescopes

[EGRET didn’t detect Draco]

S.Profumo & M.Kamionkowski, astro-ph/0601249


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  • Dwarfs: general features of Fermi vs ACT

  • dark matter search sensitivity

CACTUS signal  huge cross section

ACT Limitation: low-energy threshold

ACT Asset: Great sensitivity to final states producing hard GR spectrum!


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  • Dwarfs: Fermi results (T. Jeltema’s talk)

Preliminary

  • * Asset of Fermi: sensitivity to

  • Inverse Compton Gamma Rays!

  • * Large Uncertainties on Diffusion

  • in small extragalactic systems!


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  • Dwarfs: Comparing MAGIC and Fermi

Preliminary

  • * Even without IC, the Fermi survey-mode

  • gives it an edge over ACTs

  • * Comparable sensitivities for m~1 TeV,

  • ~100h ACT obs. time


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  • Dwarfs: prospects for ACTs in the Fermi era

Is it worth it for

ACTs to observe

local dSph to search

for DM in the

Fermi era?

YES: one example:

DM model that fits

positron excess

TeV particle mm

Large Diffusion in dSph

makes ACT much

better than Fermi!


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  • Dwarfs: prospects for ACTs in the Fermi era

Another example:

Standard Neutralino-

type DM particle,

negligible IC

m~1 TeV, comparable

sensitivities for

Fermi vs ACTs

m~5 TeV, ACTs can

outperform Fermi


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2. Clusters: a new gamma-ray source class?

* Largest bound dark matter structures

* Non-thermal activity detected as synchrotron radio emission

* Likely source of gamma rays from

hadronic or leptonic primary cosmic rays

* Not conclusively detected so far in gamma rays

* Excess hard X radiation detected in a few cases

Galaxy Cluster Abell 1689 Warps Space Credit: N. Benitez (JHU)


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2. Clusters: non-thermal activity from cosmic rays

Ophiuchus cluster (hard X-ray from Integral, new radio data)

Leptonic Scenarios alone fail to provide self-consistent explanation

Potential complementarity between Fermi and ACTs

Perez-Torres, Zandanel, Guerrero, Pal, Profumo, Prada and Panessa (2009)


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2. Clusters: new physics versus cosmic rays

Signal from DM and from CR

in local clusters of galaxies

predicted to be comparable!

Jeltema, Kehaijas and Profumo (2009)


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2. Clusters: new physics versus cosmic rays

Most promising targets for

New Physics: nearby

(gas-poor) galaxy groups!

Jeltema, Kehaijas and Profumo (2009)


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2. Clusters: ACT and Fermi searches

H.E.S.S. Collaboration, A&A, astro-ph 0907.0727 (~8h observations)


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2. Clusters: ACT and Fermi searches

Preliminary

Again, Fermi signal

dominated by IC,

HESS by FSR

More targets, biased

towards those where

the DM/CR ratio is

larger, and brighter

See Tesla Jeltema’s talk; paper in preparation by Fermi Coll.


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3. The Milky Way Center and fundamental physics

Rich and complicated Region, with several sources,

large diffuse emission, non-thermal activity


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3. The Milky Way Center and fundamental physics

ACT and Fermi observations of Sag A* of fundamental importance

to understand background to the (possibly) brightest DM source


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3. The Milky Way Center and fundamental physics

In the limit of perfect control over the diffuse and Sag A* “background”

Fermi can determine fundamental properties of DM from the GC

Jeltema and Profumo (2008)


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3. The Milky Way Center and fundamental physics

Self-consistent treatment of both the Sag A* source and DM emission

must however include a multi-wavelength approach

Regis and Ullio (2008)


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3. The Milky Way Center and fundamental physics

With certain assumptions on magnetic fields at the GC,

and on the DM annihilation final state

Radio and X-ray data put the gamma-ray emission beyond Fermi sensitivity,

marginally detectable by a CTA

Regis and Ullio (2008)


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4. Electrons and Positrons

Great data delivered by H.E.S.S.

on high-energy e+e- flux

Help understanding spectrum

and origin of HE e+e-

Relevance to New Physics:

1. Claim of anomalous

features related to e+ excess

2. Feeds back to diffuse

galactic gamma ray emission


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4. Electrons and Positrons

Bottom line of Fermi

e+e- analysis:

* Hard spectrum

* Compatible with

diffuse CR models

* Positron excess

requires extra

primary source

Is there an “anomalous feature” in the Fermi data alone?


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Is there a residual

“anomalous spectral feature”

in the Fermi data?

Most probably NO: in the ~ TeV range

  • CR Source Spectrum Cutoff

  • Diffusion Radius comparable

  • to mean SNR separation 

  • source stochasticity effects!

  • [breakdown of spatial continuity

  • and steady-state hypotheses]

1-s band for large

set of random

SNR realizations


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4. Electrons and Positrons: role of ACT’s

  • Maximize overlap with Fermi data at >TeV

  • Check for potential Anisotropy?

  • Cross check HESS results with other ACT

  • Re-calibrate ACT results after Fermi data with GR sources

  • Follow-up on potential local sources of e+e-


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Conclusions

New Physics with ACTs in the Fermi Era

  • Complementary Observations

  • (e.g. dwarfs, clusters, GC, e+e-)

  • ACTs: Potential for Discovery

  • even in Fermi era

  • (e.g. clusters as new GR sources, dwarfs)

  • Fundamental to understand

  • and control Background

  • (e.g. clusters, GC, e+e-)