Presentazione di PowerPoint

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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. LL- 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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WIMP annihilation also produces stable Electrons
and Positrons, which diffuse and loose energy
Inverse Compton off CMB and starlight photons,
Bremsstrahlung and Synchrotron emission produce
radiation from radio to gamma-ray frequencies
1. Source Term
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Annihilation debris an unavoidable consequence
of thermal WIMPs
Gamma Rays
1. Primary
2. Secondary

• Inverse Compton (eg?eg)
• (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
Wm
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
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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 ACTs 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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1. Dwarfs a lesson from CACTUS

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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1. Dwarfs a lesson from CACTUS

Excess Counts !!!
An important lesson dSph are ideal targets for
indirect DM searches
Moreover ACTs are complementary to
satellite-based GR telescopes EGRET didnt
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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1. Dwarfs Fermi results (T. Jeltemas talk)

Preliminary

• Asset of Fermi sensitivity to
• Inverse Compton Gamma Rays!
• Large Uncertainties on Diffusion
• in small extragalactic systems!

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1. Dwarfs Comparing MAGIC and Fermi

Preliminary

• Even without IC, the Fermi survey-mode
• gives it an edge over ACTs
• Comparable sensitivities for m1 TeV,
• 100h ACT obs. time

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1. 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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1. Dwarfs prospects for ACTs in the Fermi era

Another example Standard Neutralino- type DM
particle, negligible IC
m1 TeV, comparable sensitivities for Fermi vs
ACTs
m5 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, AA, 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 Jeltemas 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
ee- flux Help understanding spectrum and origin
of HE ee-
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 ee- 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 ACTs

• Maximize overlap with Fermi data at gtTeV
• 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 ee-

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Conclusions New Physics with ACTs in the Fermi Era

• Complementary Observations
• (e.g. dwarfs, clusters, GC, ee-)
• 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, ee-)

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