Constraining Dark Matter Annihilation to Gamma Rays and Charged

Transcription

Constraining Dark Matter
Annihilation to Gamma Rays
and Charged Particles
Thomas Jacques
Based on work with
N. Bell, J. Beacom, G. Mack, H. Yuksel
2009-07, Seattle
Introduction
Existence √
Rotation Curves,
Gravitational Lensing, Bullet
Cluster, Cosmic Microwave
Background, Big Bang
Nucleosynthesis, Large
Scale Structure, etc.
Thomas Jacques - INT 09-2A
2009.06
Indirect Detection
Properties?
Plenty of candidates - Which is DM?
Indirect detection often focuses on choosing a model, and comparing
predicted flux to observed flux
Great for testing a model, not so great for finding the nature of DM
2009.06
Indirect Detection
Properties?
Plenty of candidates - Which is DM?
Indirect detection often focuses on choosing a model, and comparing
predicted flux to observed flux
Great for testing a model, not so great for finding the nature of DM
So, what can we deduce about DM, in a model independent
way, from it’s annihilation flux?
Great progress in recent years; A number of bounds on
annihilation cross section/decay width
We expand and strengthen these limits, focusing on two final
states, γγ and e+e-, and determining conservative upper limits on
the annihilation cross section 〈σAv〉, so we can be confident
that these are robust upper limits
2009.06
Previous Bounds
2009.06
γγ
χ
χ
γ
χ
γγ
γ
Photon line
‘Smoking Gun’
χ
Fairly Universal, even if small branching
Don’t know branching ratio:
Gives an upper limit for this channel only
from Mack, Jacques, Beacom, Bell, Yuksel; Phys.Rev.D78:063542 (2008)
2009.06
Annihilation Flux
Annihilation flux from a nearby source:
dΦγ
1
= !σA v"Br(γγ)
dE
2
!
0
R
2
ρ(s)
dNγ
d%
4πm2χ dE
2009.06
Annihilation Flux
dΦγ
1
= !σA v"Br(γγ)
dE
2
!
0
R
2
ρ(s)
dNγ
d%
4πm2χ dE
Flux in some direction depends on:
2009.06
Annihilation Flux
dΦγ
1
= !σA v"Br(γγ)
dE
2
!
0
R
2
ρ(s)
dNγ
d%
4πm2χ dE
Cross section,
2009.06
Annihilation Flux
dΦγ
1
= !σA v"Br(γγ)
dE
2
!
0
R
2
ρ(s)
dNγ
d%
4πm2χ dE
Cross section,
Integral along the line of sight of the DM density squared,
2009.06
Annihilation Flux
dΦγ
1
= !σA v"Br(γγ)
dE
2
!
0
R
2
ρ(s)
dNγ
d%
4πm2χ dE
Cross section,
Integral along the line of sight of the DM density squared,
The γ-ray spectrum per annihilation (Dirac delta)
2009.06
Annihilation Flux
!σA v"γγJ∆Ω 1 dNγ
dΦγ
=
dE
2
J0 4πm2χ dE
2009.06
Density profiles
Minimize uncertainty
by looking at large
angular regions
Focus on conservative
Kravtsov profile, but
show results for other
profiles
NFW and Einasto
profiles most widely
used in literature
1
30
2009.06
Observation Regions
Galactic Center
Our main flux source; lots of data
M31 (Andromeda)
Relatively weak upper limits on 〈σAv〉
Analysis very similar to GC case
Cosmic Annihilation
Diffuse photon flux from extragalactic DM
annihilation
Analysis includes integral over redshift,
photon attenuation, DM clumping factor
2009.06
Data
Use data from INTEGRAL, COMPTEL, EGRET, HEGRA,
CELESTE, HESS, SMM
Cover broad range of energies: ~10-5 to ~104 GeV
2009.06
Results
-20
10
1
31
-22
M
10
A
GR
CE
LE
ST
E
HE
Results more general than they appear:
We integrate the signal over a large
energy bin, so results are valid for an
annihilation spectrum as wide as our
analysis bin (0.4 in log10 E)
EG
RE
T
M
31
10
SS
HE
Very conservative analysis
E
IDG
R
GC
-26
10
10
UND
RO
TON
KG
BAC
HO
P
USE
-28
F
DIF
RO
MW
CG
-30
At worst, our limit would be increased
by a factor of several for a broad
annihilation spectrum (except for
INTEGRAL/HEGRA)
RA
L
10
IN
TE
G
3 -1
< "Av >## [cm s ]
-24
M3
-32
10
-34
10
-5
10
10
-3
-1
10
10
m! [GeV]
1
10
3
10
5
2009.06
Results
-16
10
-18
ity
10
r
ita
Un
T
K
K
< "Av >total [cm s ]
10
d
3 -1
un
Bo
Using Br(γγ) = 10-4,
find a limit on the
total cross section
-20
Neutrinos
Gamma Rays
-4
Br($$!=1
Br(##!=10
-22
10
-24
10
-26
Natural Scale
10
-28
10
-30
10
Thomas Jacques - INT 09-2A 2009.06
-5
10
10
-3
-1
10
10
m! [GeV]
1
10
3
10
5
Positron Excess
PAMELA Positron excess
Nature 458, 607-609
Fermi e+e- excess
Phys. Rev. Lett. 102, 181101 (2009)
2009.06
Positron Excess
from N. Bell & T. Jacques; Phys.Rev.D79:043507 (2008)
2009.06
Positron Excess
Nearby Pulsars?
Dark Matter Annihilation?
No antiproton excess
Large annihilation cross section
2009.06
Positron Excess
Nearby Pulsars?
Want to constrain
annihilation to e+eLook for associated
gamma-ray emission
2009.06
Positron Excess
Nearby Pulsars?
Internal Bremsstrahlung
Want to constrain
annihilation to e+eLook for associated
gamma-ray emission
χ
e−
χ
e+
No dependence on Magnetic field,
ISRF, Diffusion
Hard gamma rays near the endpoint,
and background decreases with
energy
2009.06
Internal Brem Spectrum
Similar to analysis for gamma-gamma case
-1
Different spectrum
!σA v" J∆Ω 1 dNγ
dΦγ
=
dE
2
J0 4πm2χ dE
10
s=4mχ2
s’=4mχ(mχ-E)
!
α
dσIB
ln
= σtot ×
dE
Eπ
"
!
s
m2e
#
2
1 dσIB
dNγ
=
dE
σtot dEγ
E dNγ /dE [GeV annihilation ]
100
−1
1
$!
100
E [GeV]
1000
" ! #2 $
s
1+
s
Beacom, Bell, Bertone, Phys.Rev.Lett.94:171301 (2005)
2009.06
-16
10
Un
ita
-18
d
3 -1
T
KK
un
Br(ii ) < σAv >total [cm s ]
Bo
Constraints
y
rit
10
-20
10
-22
+ -
10
τ τ
νν
+ -
-24
µ µ
10
-26
Natural Scale
10
+ -
e e
-28
10
γγ
-30
10
-20
E
ST
LE
CE
.S
H.E
.S.
-22
10
-2
-1
0
1
2
3
4
10 10 10 10 10 10
mχ [GeV]
-23
-24
10
10
-3
10 10 10
ET
10
-21
EG
3 -1
<σAv>e+e- [cm s ]
10
10
-32
10
R
10
-25
-26
10
-27
10
L
TE
P
M
Natural Scale
CO
-28
10
-3
10
-2
10
-1
10
0
1
10 10
mχ [GeV]
2
10
3
10
4
10
5
Thomas Jacques - INT 09-2A 2009.06
5
Helicity Suppression
S-wave annihilation of Majorana particles to fermion
pairs is often suppressed by a factor of mf2
IB emission of hard gamma rays from the propagator can
lift this suppression, making Br(f f γ) significantly larger
than Br(f f)
χ
e−
χ
γ
γ
χ
e+
e−
χ
e+
This would improve our limits by a significant factor
eg Bergstrom, Phys.Lett.B 225, 372 (1989)
Bringmann, Bergstrom, Edsjo, JHEP 0801, 049 (2008)
2009.06
Comparison
Cirelli, Kadastik, Raidal & Strumia arXiv:0809.2409
2009.06
Summary
We have placed model independent constraints on the
Dark Matter annihilation cross section to various final
states
Examined γγ, e+e-, µ+µ-, τ+τγγ constraints valid for moderately broad annihilation
spectra
Extremely conservative analysis
2009.06

Constraining Dark Matter Annihilation to Gamma Rays and Charged

Transcription

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