Probing dark matter with cosmic rays and AGN jetsactive.pd.infn.it/g4/seminars/2012/files/ubaldi.pdf · cosmic rays and AGN jets Phys.Rev. D82 (2010) 123514, arXiv:1008.2230 JCAP

Lorenzo Ubaldiwith Stefano Profumo and Mikhail Gorchtein

SCIPP & Department of Physics, University of California, Santa Cruz

Bethe Center for Theoretical Physics & Physikalisches Institut der Universität Bonn, Germany

CEEM, Indiana University, Bloomington, IN

Padova - January 11, 2012

Probing dark matter with cosmic rays and AGN jets

Phys.Rev. D82 (2010) 123514, arXiv:1008.2230JCAP 1108 (2011) 020, arXiv:1106.4568

,

Wednesday, January 11, 2012

Conventional paradigm for indirect dark matter searches with gamma rays

• Pair annihilation•Decay


Conventional paradigm for indirect dark matter searches with gamma rays

• Pair annihilation•Decay

Can we search for a new signature?


The idea

• Study scattering processes of high-energy electrons (or protons) off of dark matter with emission of photons.

•Can we detect such photons?


Where should we look?


Where should we look?Two requirements:1. Source of high energy electrons and/or

protons2. Region with high density of dark matter


Where should we look?Two requirements:1. Source of high energy electrons and/or

protons2. Region with high density of dark matter

Two potentially good candidates:1. Galactic center2. Active Galactic Nuclei (AGN)


Some extra motivation


Some extra motivationelectron (proton) - DM

scatteringDM pair annihilationvs

Pros and Cons




Pros and Cons

Difficult background Difficult background




Pros and Cons





Pros and Cons


Signal prop. to Signal prop. to ρ ρ2




Pros and Cons






Pros and Cons


Happens for asymmetric DM

Does not happen for asymmetric DM





Pros and Cons








Pros and Cons






PART IOur galaxy


Facts•There are cosmic rays

Text

•There are high densities of DM

Text

PRL 106, 201101 (2011)


Very rough estimatesLocal rate per unit target for a generic WIMP model

mX ~ 100 GeV



mX ~ 100 GeV

DM pair annihilation

qχχ ≡ σχχ nχ vrel

σχχ ∼ α2

m2EW

∼ (few)× 10−36 cm2

nχ ∼ 3× 10−3 cm−3

vrel ∼ 10−3c

qχχ ∼ few × 10−31 s−1



mX ~ 100 GeV



σχχ ∼ α2

m2EW

∼ (few)× 10−36 cm2

nχ ∼ 3× 10−3 cm−3

vrel ∼ 10−3c

qχχ ∼ few × 10−31 s−1

Cosmic ray - DMscattering

qeχ→eχγ ≡Edφe

dE

1 GeV

× σeχ→eχγ

Edφe

dE

1 GeV

∼ 4× 10−1 1

cm2 s

σeχ→eχγ ∼ α3

m2EW

∼ (few)× 10−38 cm2

qeχ→eχγ ∼ few × 10−38 s−1

→ few × 10−34 s−1enhancements?



mX ~ 100 GeV



σχχ ∼ α2

m2EW

∼ (few)× 10−36 cm2

nχ ∼ 3× 10−3 cm−3

vrel ∼ 10−3c

qχχ ∼ few × 10−31 s−1

Cosmic ray - DMscattering

qeχ→eχγ ≡Edφe

dE

1 GeV

× σeχ→eχγ

Edφe

dE

1 GeV

∼ 4× 10−1 1

cm2 s

σeχ→eχγ ∼ α3

m2EW

∼ (few)× 10−38 cm2

qeχ→eχγ ∼ few × 10−38 s−1

→ few × 10−34 s−1enhancements?



• It seems that the rate is prohibitively low



•Too low for models of asymmetric dark

matter (often even further suppressed by

some dark sector scale Λ ~ TeV)



•Too low for models of asymmetric dark

matter (often even further suppressed by

some dark sector scale Λ ~ TeV)

•Are there DM models that allow for

enhancements?


The die-hard MSSMe,q

χ

e, q

e,q

χ

γ


The die-hard MSSMe,q

χ

e, q

e,q

χ

γ

Two enhancements for this process:

1.when the exchanged selectron (squark) goes on shell

2.log enhancement when the photon is collinear with the

electron (quark)


The ideaThe ingredients

Results for electronsProtons

Conclusions

DM distributionElectrons in the jetDifferential cross section

Differential cross section - The resonances

20 50 100 200

E [GeV]

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

d2!

/ d

E"

d#

[G

eV

-3]

50 100 200

E [GeV]50 100 200

E [GeV]

E" = 10 GeV E

" = 30 GeV E

" = 50 GeV

Lorenzo Ubaldi Probing dark matter with AGN jets

Mχ = 60 GeV Me = 100 GeV

Resonances in the cross section


The photon flux

dN

dEγ= r⊙ρ⊙J

1

Mχ

dΩγ

dEe

dφ

dEe

d2σ

dΩγdEγ

J =2π

∆Ω

∆Ωdθ sin θJ(θ) ∆Ω ∼ 10−3

J(θ) =

2r⊙

0ds

1

r⊙ρ⊙ρ(r(s, θ))f(r(s, θ))

to account for higher cosmic ray flux in the vicinity of galactic center

Cosmic ray electron flux

Einasto profile

angle of observation from earth

differentialcross section

angle between emitted photons and cosmic rays incident on DM


From cosmic ray electrons

0.2 1 3E! [GeV]

10-10

10-9

10-8

10-7

10-6E !

2 dN

/dE !

[MeV

cm

-2 s-1

sr-1

]

M" = 10 GeV, Me = 10.5 GeV

M" = 10 GeV, Me = 11 GeV

M" = 50 GeV, Me = 51 GeV


0.2 1 3E! [GeV]

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-3

E !2 d

N/d

E ! [M

eV c

m-2

s-1 sr

-1] electrons

protonsFermi EGB data

Fermi-LAT collaboration, Phys.Rev.Lett. 104 (2010) 101101

A different perspective...



We are about 4 orders of magnitude below the isotropic diffuse background,

this is hopeless!



this is hopeless!

But the spectral feature is sharp and this process is not isotropic, its

intensity correlates with the product of cosmic-ray density times dark

matter density. Give the Fermi-LAT enough observation time and we

might hope to detect this signature.



this is hopeless!

But the spectral feature is sharp and this process is not isotropic, its

intensity correlates with the product of cosmic-ray density times dark

matter density. Give the Fermi-LAT enough observation time and we

might hope to detect this signature.

The pess

imistic s

tudentThe optimistic professor


PART IIAGN


Where it all beganBloom and Wells had this original idea in 97/98.

Phys.Rev. D57 (1998) 1299-1302

• Active Galactic nuclei live in the densest regions of the largest DM halos and are sources of powerful and collimated jets containing ultra relativistic electrons and protons.

• Study the scattering of those high energy particles off of the DM with photons in the final state.


AGN candidates

Requisites for the AGN• Close by• Jet at an angle with the

line of sight

Centaurus A and M87 the best candidates.


Calculating the photon fluxdN

dEγ=

δDM

1

d2AGN

dΦAGNe

dEe

1

Mχ

d2σe+χ→γ+...

dΩγdEγ

cos θ0

dEe



dEγ=

δDM

1

d2AGN

dΦAGNe

dEe

1

Mχ

d2σe+χ→γ+...

dΩγdEγ

cos θ0

dEe

1. DM profile δDM =

r0

rmin

ρDM(r)dr



dEγ=

δDM

1

d2AGN

dΦAGNe

dEe

1

Mχ

d2σe+χ→γ+...

dΩγdEγ

cos θ0

dEe

2. Electron energy distribution in the jet.



dEγ=

δDM

1

d2AGN

dΦAGNe

dEe

1

Mχ

d2σe+χ→γ+...

dΩγdEγ

cos θ0

dEe

3. Differential cross sectione,q

χ

e, q

e,q

χ

γ


1. The DM profileδDM =

r0

rmin

ρDM(r)dr

We consider the theoretically motivated profile for the inner region of the AGN by Gondolo and SilkPhys.Rev.Lett. 83 (1999) 1719-1722

ρDM(r) =ρ(r)ρcore

ρ(r) + ρcorewhere ρcore Mχ/(σv0tBH)


1.1 The DM profileNormalization

We require that the DM enclosed in 105 RS does not exceed the uncertainty over the black hole mass

.

105RS

rlow

dr4πr2ρDM ≤ 3× 107 M⊙

MBH = (5.5± 3.0)× 107M⊙


δDM =

r0

rmin

ρDM(r)dr

10-4

10-3

10-2

10-1

100

101

r [pc]

108

1010

1012

1014

1016

!D

M [M

sun /

pc3

]

<"v>0 = 10

-26 cm

3/s, t

BH = 10

10 yr

<"v>0 = 10

-26 cm

3/s, t

BH = 10

8 yr

<"v>0 = 10

-30 cm

3/s, t

BH = 10

10 yr

<"v>0 = 10

-30 cm

3/s, t

BH = 10

8 yr

0 0.5 1 1.5 2#

107

108

109

1010

1011

1012

$D

M [

Msu

n /

pc2

]

10 100 1000rmin

/ RS

108

109

1010

1011

1012

$D

M [M

sun /

pc2

]

Centaurus A


2. The electron energy distribution

Blob geometry: the electrons move isotropically in the blob frame with a power law energy distribution, and the blob itself moves with respect to the central black hole with a moderate bulk Lorentz factor.

dΦAGNe

dγ (γ) =1

2keγ

−s1

1 +

γ

γbr

s2−s1−1

for γmin ≤ γ ≤ γ

max


2. The electron energy distribution

Blob geometry: the electrons move isotropically in the blob frame with a power law energy distribution, and the blob itself moves with respect to the central black hole with a moderate bulk Lorentz factor.

dΦAGNe

dγ (γ) =1

2keγ

−s1

1 +

γ

γbr

s2−s1−1

for γmin ≤ γ ≤ γ

max

Le ∼ 1043 − 1046 erg/s

Normalization from kinetic power of the jet


3. The differential cross section

e,q

χ

e, q

e,q

χ

γ

dN

dEγ=

δDM

1

d2AGN

dΦAGNe

dEe

1

Mχ

d2σe+χ→γ+...

dΩγdEγ

cos θ0

dEe

dN

dEγ= r⊙ρ⊙J

1

Mχ

dΩγ

dEe

dφ

dEe

d2σ

dΩγdEγ

In PART I we integrated over the final photon angle:

Now, in PART II the angle is fixed:


108 109 1010 1011 1012 1013

Eγ [eV]

108 109 1010 1011 1012 1013

Eγ [eV]

10-15

10-14

10-13

10-12

10-11

10-10

ν S ν

[erg

s-1 c

m-2

]

1022 1023 1024 1025 1026 1027

ν [Hz]

10-15

10-14

10-13

10-12

10-11

10-10

ν S ν

[erg

s-1 c

m-2

]

1023 1024 1025 1026 1027 1028

ν [Hz]

δDM = 109 Msunpc-2, L = 3x1045 erg s-1

δDM = 1010 Msunpc-2, L = 3x1045 erg s-1

Me = 100 GeVM

χ = 60 GeV

Fermi HESS

Fermi Fermi

Fermi

HESS

HESS

HESS

Me = 110 GeV

Me = 510 GeVMe = 305 GeV

Mχ = 95 GeV

Mχ = 500 GeVM

χ = 300 GeV

Centaurus A, SUSY scenario


(GeV)χ∼

m0 50 100 150 200 250

m (

Ge

V)

∆

0

50

100

150

200

250

-2 GeV pc M10 = 10DMδ

= [2, 5]GeVγE

= [5, 10]GeVγE

= [10, 30]GeVγE

= [30, 50]GeVγE

(GeV)χ∼

m0 50 100 150 200 250

m (

Ge

V)

∆

0

50

100

150

200

250

-2 GeV pc M11 = 10DMδ

= [2, 5]GeVγE

= [5, 10]GeVγE

= [10, 30]GeVγE

= [30, 50]GeVγE

FIG. 4: Contours of 95% CL constraint on the mχ −∆m plane based on one year of observation

of Centaurus A by the Fermi LAT. The colored regions indicate constraints from each energy bin

reported by Fermi, and the black dashed line indicates me = 100 GeV. The two panels assume

different δDM, as indicated.

In Figure 4, we plot the 95% CL bounds in the plane of mχ and ∆m, where

∆m ≡ me −mχ (28)

is the mass splitting between the neutralino and selectron. The upper panel corresponds to δDM =

1010 M⊙ pc−2, and the lower to δDM = 1011 M⊙ pc−2. These values correspond to a neutralino

annihilation cross section of σv ∼ 10−30 cm3 s−1 (appropriate for a coannihilation scenario) and a

black hole lifetime of tBH ∼ 108 or 1010 years, respectively. We continue to assume a bino neutralino

and selectrons which are degenerate in mass. Since the optimal energy bin for the search varies

with mχ and me, we derive the constrained region from each energy bin independently, as indicated

on the figure. We find that the largest resolving power comes from the highest energy bins, but

11

Text

Huang, Rajaraman, Tait arXiv:1109.2587

Constrain the MSSM


http://inspirehep.net/author/Huang%2C%20Jinrui?recid=927088&ln=en

http://inspirehep.net/author/Huang%2C%20Jinrui?recid=927088&ln=en

http://inspirehep.net/author/Rajaraman%2C%20Arvind?recid=927088&ln=en

http://inspirehep.net/author/Rajaraman%2C%20Arvind?recid=927088&ln=en

http://inspirehep.net/author/Tait%2C%20Tim%20M.P.?recid=927088&ln=en

http://inspirehep.net/author/Tait%2C%20Tim%20M.P.?recid=927088&ln=en

Anything else?• We also considered UED models. Results and

conclusions are very similar to the MSSM.• We studied scattering of protons off of DM

but they should be treated more carefully.

The ideaThe ingredients

Results for electronsProtons

Conclusions

Protons - Compare to data

108

109

1010

1011

1012

1013

E! [eV]

108

109

1010

1011

1012

1013

E! [eV]

1023

1024

1025

1026

1027

" [Hz]

10-25

10-23

10-21

10-19

10-17

10-15

10-13

10-11

" S" [

erg s

-1 c

m-2

]

1023

1024

1025

1026

1027

" [Hz]

Ep = 100 GeV

Ep = 1000 GeV

Ep = 10000 GeV

E-2

energy distribution

Mq = 310 GeV

M# = 100 GeV

FermiHESS

FermiHESS

Mq = 310 GeV

M# = 300 GeV

Centaurus A, protons, SUSY

Lorenzo Ubaldi Probing dark matter with AGN jets


Conclusions


Conclusions

• We studied gamma-ray spectra coming from the scattering of high energy electrons off of dark matter.


Conclusions


• Looking at the galactic center, it seems that this signal is quite low, although, if you wanted to be optimistic, you would say it might be possible to detect the feature.


Conclusions


• Looking at the galactic center, it seems that this signal is quite low, although, if you wanted to be optimistic, you would say it might be possible to detect the feature.

• Looking at AGN, we might be in the right ballpark for Fermi, but the astrophysical uncertainties are large and not completely understood.


Documents

Probing dark matter with cosmic rays and AGN jetsactive.pd.infn.it/g4/seminars/2012/files/ubaldi.pdf · cosmic rays and AGN jets Phys.Rev. D82 (2010) 123514, arXiv:1008.2230 JCAP