GLAST and Dark Matter

Jan Conrad

Stockholm University

Representing the GLAST-LAT Working group for Dark Matter and New Physics

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope

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 field of view Large energy range sub-arcmin source localization Energy resolution @ 10 GeV < 6 %.

Two GLAST instruments:

LAT (Large Area Telescope): 20 MeV – >300 GeVGBM (GLAST Burst Monitor) 10 keV – 25 MeVLaunch: February, 2008).5-year mission (10-year goal)

Large Area Telescope (LAT)

GBM

the Swedish

astronaut

LAT FoV

GBM FoV

e+ e– Calorimeter

Particle tracking detectors

Conversion foils

Anticoincidenceshield

Detection technique

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)*

e+ e–

Overview of Large Area Telescope

Precision Si-strip TrackerPrecision Si-strip 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 CalorimeterHodoscopic 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

Segmented Anticoincidence DetectorSegmented Anticoincidence Detector

89 plastic scintillator tiles. Reject background of charged cosmic rays; segmentation reduces self-veto effects at high energy.

EGRET: monolithic ACD: self-veto due to backsplash

Calorimeter

Tracker

ACD [surrounds 4x4 array of TKR towers]

Field of View factor 4 Point Spread function factor > 3 effective area ( factor > 5Results in factor > 30 improvement in sensitivity Results in factor > 30 improvement in sensitivity below < 10 GeV, and >100 at higher energies.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

Sweden Royal Institute of Technology (KTH), Stockholm University, Kalmar University

Principal Investigator: Principal Investigator: Peter MichelsonPeter Michelson (Stanford & SLAC)

~270 Members (includes ~90 Affiliated Scientists,37 Postdocs,

and 48 Graduate Students)

GEANT4 detector simulation

High-energy interacts in LAT

Black: Charged particlesWhite: PhotonsRed: Deposited energyBlue: Reconstructed tracksYellow: Inferred γ direction

Simulation:Detailed geometryover 45,000 volumes, and growing! Interaction Physics:QED: derived from GEANT3 with extensionsto higher and lower energies (alternatemodels available)

Hadronic: based on GEISHA (alternatemodels available) and currently tested on beam test data

PropagationFull treatment of multiple scatteringSurface-to-surface ray tracing. δ electrons

Digitization:Includes information from actual LAT tests detailed instrument response dead channels noise etc.

Deadtime Effects F. Longo

Some photon candidates (in the calibration unit)

Gamma Ray Large Area Space Telescope science menu

0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV0.01 GeV 0.1 GeV 1 GeV 10 GeV 100 GeV 1 TeV

Gamma Ray Bursts

Unidentified sources

Cosmic ray acceleration

Active Galactic Nuclei

Dark matter (neutralinos, axions etc,

etc…)

Solar flares

Pulsars

Strange Quark Matter ?

Quantum

Gravity ?

Background to all photons: charged particles

T. A. Porter et al. 30th ICRC, Merida, Mexico

- 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.613:956-961,2004

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.

Photon background: galactic diffuse - conventional and optimized GALPROP model

’conventional’ GALPROP: calibrated with locally measured electron and

proton,helium spectra, as well as synchroton emission

’optimized’ GALPROP: see next slide

Strong, Moskalenko, Reimer, ApJ 537, 736, 2000

Strong, Moskalenko, Reimer, ApJ 613, 962-976, 2004

Conventional OptimizedRegarding EGRET GeV excess:

Stecker, Hunter, Kniffen e-Print: arXiv:0705.4311 [astro-ph]

EGRET excess instrumental, i.e. disappears with correct calibration

Porter, Atwood, Baughman, JohnsonICRC 2007 e-Print: arXiv:0706.0220 [astro-ph]

EGRET excess becomes larger if cp bg taken into account

http://galprop.stanford.edu/web_galprop/galprop_home.html

”Optimized model”: allow average CR spectrum to deviate from local spectrum

Use antiprotons to constrain average proton spectrum

Electrons adjusted to recover EGRET

galactic diffuse con’t

slide from Igor Moskalenko

GLAST complementary searches

Search Technique advantages challenges

Galactic center

Good Statistics

Source confusion/Diffuse background

Satellites, subhalosPoint sources

Low background,Good source id

Low statistics

Milky Way halo

Large statistics

Galactic diffuse background

Extra-galactic

Large Statistics

Astrophysics, galactic diffuse background

Spectral lines No astrophysical uncertainties, good source id

Low statistics

See talk by Pieri

Generic WIMP flux

γ yield per annihilation

Flux from given source

line continuum

Dark Matter structure

Annihilation cross setcion. Constraint by cosmology to ~ 10-26 cm2

ISASUGRA

Galactic center (strategy)

Assume a NFW profile

Simulate WIMP signal

Simulate background (optimized/conventional galprop)

Simulate GLAST response (ObsSim)

Choose ROI (0.5 degrees, E > 1 GeV)

Check if WIMP + background can be distinguished

from background only (using χ2 for simplicity).

GC: sensitivity

”Exc

luded

” by

EGRET

1)

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

Simulate response to monoenergetic line (ObsSim)

5 years of operation

Check if line+background can be distinguished from background only using:

Vary s until ”averaged (bootstrapped) Δχ > 25 ( 5 σ)

)()( 2min

2min

2 bbs No assumptions on where this line comes from

Line 5σ sensitivity (5 year observation)

Simulated detector response to δ function in energy

10-9

10-8

Y. Edmonds, E. Bloom, J. Cohen-Tanugi

Conventional background

Semi-analytic models of halo substructure1)

Signal, background flux (ObsSim) inside the tidal radius as measure of significance

WIMP mass = 100GeV

Signficance [ σ]

No

. o

f sa

tell

ites

Satellites/Subhalos

GLAST 1-yr

GLAST 5-yrs

How many sources at which significance ?

WIMP mass [GeV]

100 GeV WIMP, 10 σ detection

<σ

an

nihv >

[2.3

e.-

26

cm

-3s

-1]

P. Wang, L. Wai, E. Bloom

Green: optimized Red: conventional

1) Taylor & Babul, MNRAS, 364, 535 (2004) - MNRAS, 364, 515 (2005) -MNRAS, 348, 811 (2004)

Jan Conrad (KTH, Sthlm) La Thuile March 2007 20

Subhaloes vs. other sourcesSource Mono-

energeticQuark Spectrum

Extended Non-variable High-latitude No counterparts

Subhalos

Molecular clouds

Pulsars

Plerions

SNR

Blazars

Taylor et al. 1st GLAST symposium

Cosmological WIMP annihilation

Absorption

Particle Physics (continuum plus line yield)Cosmology

Halo structures (NFW etc. subhaloes) and halo mass function

Particle Physics (annihilation x-section)

Ullio, Bergström, Edsjö, Lacey

Phys Rev. D. 66 123502 (2002)

Cosmological WIMPS: Sensitivity

Includes charged 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.

Simple and idealized χ2

analysis

GC, 5 years

Phys Rev. D. 66 123502 (2002)

A. Sellerholm, J.C., L. Bergström, J. Edsjö

Galactic Halo

Full detector response simulation to galactic diffuse signal (plus WIMP)

Likelihood fit to both the energy and spatial distribution

Sensitivity via pseudoexperiments of 1 year GLAST operation

EG, 1 year

A. Sander, R. Hughes, P. Smith, B. Winer

LAT e+/e- detection: capabilities

Effective e+/e- detection with small hadron contamination (few percent)

Cuts based on event topology Energy resolution between 5 and 20 %

A. Moiseev

LKP1) mass = 300 GeV and 600 GeV

Single (close) clump (in principle, consider

overlap of many clumps in diffusion equation)

1) Baltz & Hooper, JCAP 7 (2007)

Reconstructed LAT electron spectrum

Illustrative example

A. Moiseev

A teaser .....

Inert Doublet model:

”Higgs Dark Matter”

extra scalar doublet, introducing three new fields (1 charged, 2 scalar)

Line flux large relative to continuum flux

Uses ObsSim with Blazar background

A. Sellerholm, J.C.

Line sensitivity in EG background

5 σ NFW

5 σ NFW plus sh

e.g.:

Barbieri et al., Phys. Rev. D 74 (2006) 0015007

Gustafsson, Lindström, Bergström,Edsjö, astro-ph/0703512 (accepted by PRL)

Jan Conrad (KTH, Sthlm) La Thuile March 2007 27

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

More (interesting ?) conclusions ...

The place to look for GLAST performance for your calculations is:

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 !

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.

www-glast.slac.stanford.edu/software/IS/glast_lat_performance.htm

Acknowledgements

The Dark Matter and New Physics WG of GLAST-LAT - in particular:

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

Jan Conrad (KTH, Sthlm) La Thuile March 2007 31

Identification of Dark Matter subhalos

Molecular cloud

Pulsar

30 GeV

WIMP

200 GeV

WIMP

Baltz, Taylor, Wai, astro-ph/0610731

5 yr GLAST, single clump, 1 degree

rejected allowed

rejectedrejected

Jan Conrad (KTH, Sthlm) Scineghe07 June 2007 32

mSUGRA exclusion (Galactic Center)

A.Morselli, E. Nuss, A. Lionetto. First Glast Symposium, 2007

Similar ”analysis” as in generic WIMP case

5yr, 3σ discovery

trunc. NFW

A0 = 0

Acc. Limits:Baer et al. hep-ph/0405210

tang = 60

A0 = 0

Sagittarius