Transcript Slide 1

Gamma-ray Large
Area Space
Telescope
GLAST and Dark Matter
Jan Conrad
Stockholm University
Representing the GLAST-LAT Working
group for Dark Matter and New Physics
Outline

The Gamma Ray Large Area Space Telescope (GLAST)
Large Area Telescope (LAT)

Complementary searches and predicted sensitivities


Galactic center, satellites, diffuse galactic, diffuse
extragalactic, lines
Bonus track: e-(e+) detection
Sensitivities are pretty much work in
progress. We are currently updating
with newest information on detector
response and backgrounds.
GLAST Key Features




Large Area
Telescope (LAT)
Large field of view
Large energy range
sub-arcmin source localization
Energy resolution @ 10 GeV < 6 %.
Two GLAST instruments:
the
Swedish
astronaut
GBM
LAT (Large Area Telescope): 20 MeV – >300 GeV
GBM (GLAST Burst Monitor) 10 keV – 25 MeV
Launch: February, 2008).
5-year mission (10-year goal)
Detection technique

Anticoincidence
shield

Conversion foils

Particle tracking
detectors
e+
e–

Calorimeter
Tracker
(detection planes + high Z
foils): photon conversion
and reconstruction of the
electron/positron tracks.
Calorimeter: energy
measurement.
Anti-coincidence shield
(ACD): background
rejection
Signature of a gamma
event:
No ACD signal
2 tracks (1 Vertex)*
Overview of Large Area Telescope

Precision Si-strip Tracker




Tracker
18 XY tracking planes. Single-sided silicon
strip detectors (228 mm pitch) Measure
the photon direction; gamma ID.
EGRET: spark chamber, large dead time,
Hodoscopic CsI Calorimeter


Array of 1536 CsI(Tl) crystals in 8 layers.
Measure the photon energy; image the
shower.
EGRET: monolithic calorimeter: no imaging
and decreased resolution
e

Segmented Anticoincidence Detector


ACD
+
[surrounds
4x4 array of
TKR towers]
89 plastic scintillator tiles. Reject
background of charged cosmic rays;
segmentation reduces self-veto effects atField of View
high energy.
EGRET: monolithic ACD: self-veto due
to backsplash
e–
Calorimeter
factor 4
Point Spread function factor > 3
effective area (
factor > 5
Results in factor > 30 improvement in sensitivity
below < 10 GeV, and >100 at higher energies.
Much smaller dead time factor ~4,000
No expendables
The GLAST-Large Area Telescope
Team

France

IN2P3, CEA/Saclay

Italy

Universities and INFN of Bari, Perugia, Pisa, Roma Tor Vergata, Trieste, ASI, INAF

Japan

Hiroshima University, ISAS, RIKEN

United States

CSU Sonoma. UC Santa Cruz, Goddard, NRL, OSU, Stanford (SLAC and HEPL),
Washington, St. Louis
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Sweden

Royal Institute of Technology (KTH), Stockholm University, Kalmar University
Principal Investigator:
Peter Michelson (Stanford & SLAC)
~270 Members
(includes ~90 Affiliated Scientists,37 Postdocs,
and 48 Graduate Students)
GEANT4 detector simulation
Simulation:
Detailed geometry
over 45,000 volumes, and growing!
High-energy  interacts in LAT
Interaction Physics:
QED: derived from GEANT3 with extensions
to higher and lower energies (alternate
models available)
Hadronic: based on GEISHA (alternate
models available) and currently tested
on beam test data
Propagation
Full treatment of multiple scattering
Surface-to-surface ray tracing.
δ electrons
Digitization:
Includes information from actual LAT tests
detailed instrument response
dead channels
noise
etc.
Black: Charged particles
White: Photons
Red: Deposited energy
Blue: Reconstructed tracks
Yellow: Inferred γ direction
Deadtime Effects
F. Longo
Some photon candidates (in the calibration unit)
Gamma
Ray
Large Area Space Telescope science menu
Active Galactic Nuclei
Unidentified
sources
Cosmic ray
acceleration
Solar flares
Pulsars
Quantum Strange Quark
Dark matter
Gravity ? Matter ?
Gamma Ray Bursts
0.01 GeV
0.1 GeV
1 GeV
10 GeV
100 GeV
(neutralinos,
1 TeV
axions etc, etc…)
Background to all photons: charged
particles
Black, total; light
green, GCR protons;
lavender, GCR He;
red, GCR electrons;
blue, albedo protons;
light blue, albedo
positrons; green,
albedo electrons; and
yellow albedo
gammas.
- Advanced MV
method
- Final rejection
power:
1/106
- γ efficiency: 0.8
Sreekumar et al.
Astrophys.J.494:523-534,1998
Strong et al.
Astrophys.J.613:956961,2004
T. A. Porter et al. 30th ICRC, Merida, Mexico
Photon background: galactic diffuse conventional and optimized GALPROP model
http://galprop.stanford.edu/web_galprop/galprop_home.html

’conventional’ GALPROP:


calibrated with locally measured electron and
proton,helium spectra, as well as synchroton emission
’optimized’ GALPROP: see next slide
Regarding EGRET GeV excess:
Conventional
Optimized
Stecker, Hunter, Kniffen
e-Print: arXiv:0705.4311 [astro-ph]
EGRET excess instrumental, i.e.
disappears with correct calibration
Porter, Atwood, Baughman, Johnson
ICRC 2007
e-Print: arXiv:0706.0220 [astro-ph]
EGRET excess becomes larger if cp bg
taken into account
Strong, Moskalenko, Reimer,
Strong, Moskalenko, Reimer,
ApJ 537, 736, 2000
ApJ 613, 962-976, 2004
galactic diffuse con’t

”Optimized
model”: allow
average CR
spectrum to
deviate from
local spectrum

Use antiprotons
to constrain
average proton
spectrum

Electrons
adjusted to
recover EGRET
slide from Igor Moskalenko
GLAST complementary searches
Search Technique
advantages
challenges
Galactic
center
Good
Statistics
Source
confusion/Diffuse
background
Satellites,
subhalos
Point sources
Low
background,
Good source id
Low statistics
Milky Way
halo
Large
statistics
Galactic diffuse
background
Extragalactic
Large
Statistics
Astrophysics,
galactic diffuse
background
Spectral lines
No astrophysical
uncertainties, good
source id
Low statistics
See talk by Pieri
Generic WIMP flux
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γ yield per annihilation
ISASUGRA
line

continuum
Flux from given source
Annihilation
cross setcion.
Constraint by
cosmology to
~ 10-26 cm2
Dark
Matter
structure
Galactic center (strategy)

Assume a NFW profile
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Simulate WIMP signal
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Simulate background (optimized/conventional
galprop)
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Simulate GLAST response (ObsSim)
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Choose ROI (0.5 degrees, E > 1 GeV)
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Check if WIMP + background can be distinguished
from background only (using χ2 for simplicity).
GC: sensitivity
1) Mayer-Hasselwander et. al.
Astron.Astrophys.335:161-172,1998
E. Nuss, A. Lionetto, A. Morselli
Senstivity to lines: procedure

Look for line signal in annulus

Assume background given by
conventional/optimized model
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Simulate response to
monoenergetic line (ObsSim)

5 years of operation

Check if line+background can be
distinguished from background
only using:
2
2
2
min
min
  

(s  b)  
Vary s until ”averaged
(bootstrapped) Δχ > 25 ( 5 σ)
(b)
No assumptions on
where this line
comes from
Line 5σ sensitivity (5 year
observation)
Conventional
background
Simulated
detector
response to δ
function in
energy
10-8
10-9
Y. Edmonds, E. Bloom, J. Cohen-Tanugi
Satellites/Subhalos

which significance ?
100 GeV WIMP, 10
σ detection
No. of satellites

Semi-analytic models of halo
substructure1)
P. Wang, L. Wai, E. Bloom
Signal, background flux (ObsSim) inside
the tidal radius as measure of significance
How many sources at
WIMP mass = 100GeV
<σannihv >[2.3e.-26 cm-3s-1]

WIMP mass [GeV]
1) Taylor & Babul, MNRAS, 364, 535
(2004) - MNRAS, 364, 515 (2005)
-MNRAS, 348, 811 (2004)
Signficance [ σ]
Green: optimized
Red: conventional
Subhaloes vs. other sources
Source
Monoenergetic
Quark
Spectrum
Extended
Non-variable
High-latitude
No
counterparts
Subhalos
Molecular
clouds
Pulsars
Plerions
SNR
Blazars
Jan Conrad (KTH, Sthlm)
La Thuile
March 2007
Taylor et20
al. 1st GLAST
symposium
Cosmological WIMP annihilation
Particle Physics
(annihilation xsection)
Halo
structures
(NFW etc.
subhaloes)
and halo mass
function
Cosmology
Ullio, Bergström, Edsjö, Lacey
Phys Rev. D. 66 123502 (2002)
Particle Physics
(continuum plus
line yield)
Absorption
Cosmological WIMPS: Sensitivity
 Includes charged
GC, 5 years
particle background
 Band corresponds to:

[EGRET]
Sreekumar et al.
Astrophys.J.494:523-534,1998

[EGRET reanalyzed]
Strong et al.
Astrophys.J.613:956-961,2004

”Blazar” model
Ullio et al.
Phys Rev. D. 66 123502 (2002)

Simple and idealized χ2
analysis
A. Sellerholm, J.C., L. Bergström, J. Edsjö
Galactic Halo

Full detector response
simulation to galactic
diffuse signal (plus
WIMP)

LikelihoodEG,
fit to
both
1 year
the energy and spatial
distribution

Sensitivity via
pseudoexperiments of
1 year GLAST operation
A. Sander, R. Hughes, P. Smith, B. Winer
LAT e+/e- detection: capabilities

Effective e+/e- detection with small hadron
contamination (few percent)

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Cuts based on event topology
Energy resolution between 5 and 20 %
A. Moiseev
Illustrative example

LKP1) mass = 300 GeV
and 600 GeV

Single (close) clump
(in principle, consider
overlap of many clumps
in diffusion equation)
Reconstructed LAT electron
spectrum
1) Baltz & Hooper, JCAP 7 (2007)
A. Moiseev
A teaser .....
Inert Doublet
model:
”Higgs Dark Matter”

Line sensitivity in EG background
e.g.:
Barbieri et al., Phys. Rev. D 74 (2006)
0015007
Gustafsson, Lindström, Bergström,Edsjö,
astro-ph/0703512 (accepted by PRL)

extra scalar
doublet, introducing
three new fields (1
charged, 2 scalar)

Line flux large
relative to
continuum flux
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Uses ObsSim with
Blazar background
A. Sellerholm, J.C.
Standard Conclusions
-The GLAST LAT team pursuis complementary
searches for signatures of particle dark matter.
-GLAST will shed light on the multi-GeV EGRET
data.
-GLAST has the potential to either discover or to
constrain particle dark matter and establish contact
between LHC discovery and Dark Matter
- GLAST will be able to image Dark Matter Halo
structure
The Galactic
center shining in
DM gamma rays
Jan Conrad (KTH, Sthlm)
La Thuile
March 2007
27
More (interesting ?) conclusions ...

The place to look for GLAST performance for your calculations
is:
www-glast.slac.stanford.edu/software/IS/glast_lat_performance.htm

Paper summarizing sensitivities in (σv,m) space for all what
has been presented today to be submitted later this year.

The official GLAST-Launch date is: Feb 5, 2007
 GLAST data will be public after one year

GLAST is not only a photon detector !
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GLAST is not only more sensitive than EGRET, but will also be
better prepared (in terms of systematics and ”instrumental”
background (however, it is not flying yet !)

There are different ways to collaborate with us, if you have
ideas do not hesitate to talk to me during ENTAPP or or go via
any other GLAST member.
Acknowledgements

The Dark Matter and New Physics WG of GLAST-LAT - in particular:
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Ted Baltz (Google), E. Bloom, Y. Edmonds, P. Wang,
L. Wai (Yahoo), J. Cohen-Tanugi(SLAC/KIPAC)
I. Moskalenko (Stanford)
A. Morselli, A. Lionetto (INFN Roma/Tor Vergata)
E. Nuss (Montpellier)
R. Hughes, A. Sander, B. Winer (Ohio State)
L. Bergström, J. Edsjö, A. Sellerholm (Stockholm)
A. Moiseev (Goddard)
Not covered:
- point sources of DM (Bertone, Rando, Morselli).
- mSUGRA exclusion (Lionetto)
BACKUP SLIDES
Identification of Dark Matter subhalos
5 yr GLAST, single
clump, 1 degree
rejected
Molecular cloud
rejected
200 GeV
30 GeV
WIMP
WIMP
rejected
Pulsar allowed
Baltz, Taylor, Wai, astro-ph/0610731
Jan Conrad (KTH, Sthlm)
La Thuile
March 2007
31
mSUGRA exclusion (Galactic Center)
A0 = 0
Similar
”analysis” as
in generic
WIMP case
5yr, 3σ
discovery
trunc. NFW
Acc. Limits:
Baer et al. hep-ph/0405210
Jan Conrad (KTH, Sthlm)
A.Morselli, E. Nuss, A. Lionetto. First Glast Symposium, 2007
Scineghe07
June 2007
32
tang  = 60
A0 = 0
Sagittarius