The search for dark matter with Fermi: a progress report

8/6/2019 The search for dark matter with Fermi: a progress report

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T e searc or ar matter w t Fermi: a progress report

Elliott BloomKIPAC SLAC, Stanford UniversityRepresenting the Fermi LAT CollaborationDark Matter 2010, Marina Del Rey, CAFebruary 24, 2010

Via Lactea II


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Special thanks to Yvonne Edmonds and Simona Murgia for valuable inputs to this

talk


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Photons from WIMP Annihilation

Note: For a decaying DM particle

mm

v 12

22

( ) f f

f ann B

dE dN

mv E

dE d

2241,,

( ))( ) dllr d los , ,, r2

Particle Physics

DM Distribution


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WIMP annihilation: gamma ray yield

200GeV mass WIMP

M WIMP Total# >100MeV >1GeV >10GeV

10 GeV 17.3 12.6 1.0 0

100GeV 24.5 22.5 12.4 1.0

1TeV 31.0 29.3 22.4 12.3

WIMP pair annihilation gamma spectrum

Gamma ray yield per

final state bb

200 MeV Threshold


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~2 12 from Aquarius and Via Lactea.

~ Best LAT PSF


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A Look at the LAT16 towers TKR+CAL+DAQ

1.8m x 1.8m x 1.0m3 tons

e+

e

Calorimete r

Tracker

ACDGrid

Data AcquisitionSystem

Anticoincidence detector (ACD) for charged particle rejection

Tracker reconstructs the direction of an incoming photon

Calorimeter for energy reconstruction and shower imaging


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; design goal is 10 years


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starting August 2008


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Fermi Science After ~ 1.5 Years

Approximately 80 Papers and Counting (AGN, Pulsars, Starburst Galaxies, GRB, diffuse background, electrons, dark matter searches ) Fermi Catalog, 1FGL Public data release, Pass 6V3

Dark matter search publications (Abdo, A. A., et al CAT I) Measurement of the Cosmic Ray e+ + e spectrum from 20 GeV to 1 TeV

with the

Fermi

Large

Area

Telescope ;

PRL;

arXiv:0905.0025 Observations of Milky Way Dwarf Spheroidal galaxies with the Fermi

LAT detector and constraints on Dark Matter models; ApJ; arXiv:1001.4531

Probing Dark

Matter

Annihilation

with

Fermi

Observations

of

Clusters

of

Galaxies; Submitted to JCAP; arXiv:1002.2239

Fermi Large Area Telescope search for photon lines from 30 to 200 GeV and dark matter implications ; PRL; arXiv:1001.4836

Constraints on

Cosmological

Dark

Matter

Annihilation

from

the

Fermi

LAT Isotropic Diffuse Gamma Ray Measurement; Submitted to JCAP; on archive soon.


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has at least 25 stars


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Fermi DM Upper Limits from Galaxy Clusters

no substructure (solid lines), a conservative substructure setup which includes only

substructure of dwarf galaxy mass or larger (dashed lines), and an optimistic setup which

includes substructure down to Mcut = 10

6 M (dot dashed lines).

B Bbar final state

Coma and Fornax clusters

All clusters with limits


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WIMP Lines, the DM smoking gun Monochromatic photons make a line in the energy

spectrum For annihilation into , or photon energy is

For annihilation into Y

Decaying WIMPs also produce lines , , , Z, Loop suppression

Branching fractions, B ,are typically in the range [10 1

,10 4

] depending on theory Limits on Y can constrain dark matter models

For line searches optimal energy resolution and accurate energy calibration are essential

m

mm E Y

4

2

m E =


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A. Ibarra & D. Tran [astro ph/0709.4593v1]Theories with Enhanced Lines

Gravitino Decay

Z line line

Inert HiggsM. Gustafsson et al . [astro ph/0703512v1]

Radiative Corrections

T. Bringmann et al . [hep ph/0710.3169v2] Particle Branching Ratios

Neutralino 3x10 -3 to 10 -5

Inert HiggsGustafsson, Lundstrom,Bergstrom, Edsjo. March2007

0.36 to 10 -4

GravitinoIbarra, Tran. Sept 2007

0.66 (85 GeV)0.05 (150 GeV)

d l


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Region and Data Selection August 7 2008 to July 21 2009 11 months Remove Galactic Plane except for GC: includes (|B|>10 ) | (|L| 20 GeV) Except within 1 of GC where no sources were removed Removes ~5% of photons

Li R l i


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Line Resolution Bottom plot

Unbinned maximum likelihood fit to Triple Gaussian

Black = IRF from fit to LAT MC Simulation (GLEAM) (20, 50, 100, 200, 300 GeV) Red = IRF from interpolation for line energies that were not simulated IRFs are normalized

FWHM ~11% 20 100GeV ~13% 150 200 GeV

Systematic error on absolute energy from beam tests for 20 300 GeV 10%, +5%


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Composite likelihood fits signal + background

S(E) = signal PDF, f = signal fraction ; B(E, ) = background PDF = power law, = index

f and free , f 0 constraint No detection at 95% CL Upper limits from MINUIT error on

signal fraction, f

Fitting

Biggest signal fit at 40 GeV

=

N

iii E B f E S f L

0

1 ),()()(

Sliding window : energy range based on resolution for Line IRFs, 4 window

Example Coverage and Power for Fitting Method


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Example Coverage and Power for Fitting Method with 100 GeV WIMP MC Input

Coverage

Power


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95% C.L. Flux Upper Limits vs. Mass


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Flux ann UL, Decay LL

Accepted for publication in PRL, A. Abdo et al. LL = LL


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Constraints on Models from Line Analysis Cross sections UL are on the order of 10 27cm 3s 1 and are of interest

in constraining models with large annihilation cross sections (e.g., Wino models)

For decaying WIMPs lifetime limits constrain some gravitino decay models with


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Latest on Wino Models Kane et at.

Gord Kane Private communication


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Summary and Conclusions

Fermi is addressing a large class of source types as DM indirect detection targets with initial results placing significant limits on particle physics models of dark matter.

Our all sky capability is a large asset in these searches (we dont need to know where to stare). The best current Fermi limits are pushing

10 25 cm 3/s with < 1 year of data from Dwarf Sp and Clusters.

We are just beginning: Fermi is a 5 10 year mission.


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Backup


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GC Slides From Simona Murgia

KIPACSLACRepresenting the Fermi LAT Collaboration


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The search for dark matter with Fermi: a progress report

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