Sergio Palomares-Ruiz
November 17, 2008
Dark Matter Annihilation/Decay
Scenarios
Novel Searches for Dark Matter with
Neutrino Telescopes
Columbus, OH (USA) November 17-19, 2008
Sergio Palomares-Ruiz
November 17, 2008
What do we know about Dark Matter?
• Astrophysicist view:
• Particle Physicist view:
Sergio Palomares-Ruiz
November 17, 2008
Sergio Palomares-Ruiz
November 17, 2008
Model-independent bound
J. F. Beacom, N. F. Bell and G. D. Mack, Phys. Rev. Lett. 99:231301, 2007
• Neutrinos are the least detectable particles of
the SM
• From the detection point of view the most
conservative assumption (the worst case) is that
DM annihilates (decays) only into ν’s:
  → νν ( → νν)
• This is not an assumption about realistic models
• It provides a bound on the total annihilation
cross section (lifetime) and not on the partial
cross section (lifetime) to neutrinos
• Anything else would produce photons, and hence
would lead to a stronger limit
Sergio Palomares-Ruiz
November 17, 2008
Strategy
• Calculate neutrino flux
• Compare potential signal with the background
Two energy regions: backgrounds
• E ~ 100 MeV – 100 TeV: atmospheric
neutrino flux
• E ~ 10 MeV – 100 MeV: invisible muons and
atmospheric neutrino flux
Signal from Annihilations
Sergio Palomares-Ruiz
November 17, 2008
d

dE
ann
Experiment

4
  dN
2
2m dE
Rsc  J
2
0
ann

Particle Physics Astrophysics
Sergio Palomares-Ruiz
November 17, 2008
Field of View



2
1cos

Neutrino Spectrum: Flavor democracy
dN2
 E

m

dE3
Average of the Line of Sight Integration of ½2





1
1


J

(
r
)
d

2
d
cos






R


1

max
ann
2

2
cos
0
sc
0
2
2
r
R

2

R
cos



sc
sc
 
2
2 2


R

R
sin

R
cos
max
halo
sc
sc
Signal from Decays
Sergio Palomares-Ruiz
November 17, 2008
d

dE
dk
Experiment

4
1
dN
m  dE
Rsc  0 J
dk

Particle Physics Astrophysics
Sergio Palomares-Ruiz
November 17, 2008
Field of View



2
1cos

Neutrino Spectrum: Flavor democracy
dN
2
E



m
/2
dE
3
Average of the Line of Sight Integration of ρ





1
1


J

(
r
)
d

2
d
cos






R


1

max
dk

cos 0
sc
0
2
2
r
R

2

R
cos



sc
sc





/







R
1

R
/
r


sc
sc
s
(
r
)




sc

r


1

r
/
r


s 



R

R
sin


R
cos

2
2 2
max
halo
sc
sc
Annihilations vs Decays
Sergio Palomares-Ruiz
November 17, 2008
• 2 DM particles
• 1 DM particle
• E = mÂ
• E = mÂ/2
• Proportional to
<¾v>/mÂ2
• Proportional to
1/¿ÂmÂ
• Proportional to ½2
• Proportional to ½
d dk
d ann  3 10 26 cm 3 / s  0.3 GeV/cm 3  m  10 26 s 



 10


  
dE
dE 


100
GeV


0



  
DM Density Profile Uncertainties
Sergio Palomares-Ruiz
November 17, 2008
Annihilations:
SPR and S. Pascoli, Phys. Rev. D77:025025, 2008
From the allowed range of:
•Local rotational velocity
•Amount of flatness
•Non-halo components
P. Belli et al. , Phys.Rev.D 66:043503, 2002
Decays:
Extreme values for the 3 profiles: Javg = (1.3, 8.1)
SPR, Phys. Lett. B665:50, 2008
Sergio Palomares-Ruiz
November 17, 2008
Energy resolution: ¢log E = 0.3
 4
 
GeV
o10
30
E

10
Ge
E
o
30
E

10
Ge
H. Yüksel, S. Horiuchi, J. F. Beacom and S. Ando,
Phys. Rev. D76:123506, 2007
Other related limits
M. Kachelriess and P. D. Serpico, Phys. Rev. D76:063516, 2007
N. F. Bell, J. B. Dent, T. D. Jacques and T. J. Weiler, Phys. Rev. D78:083540, 2008
J. B. Dent, R. J. Scherrer and T. J. Weiler, arXiv:0806.0370
G. D. Mack, T. D. Jacques, J. F. Beacom, N. F. Bell and H. Yüksel, Phys. Rev. D78:063542, 2008
Sergio Palomares-Ruiz
November 17, 2008
Can we do better?
• Careful treatment of energy resolution
and backgrounds: eg. limits on MeV DM
• We use SK data for E = 18-82 MeV
• Detection: νe + p → e+ + n
• Two main backgrounds:
– Invisible muons
– Atmospheric neutrinos
M. S. Malek, Ph.D thesis
M. S. Malek et al., Phys. Rev. Lett. 90:061101, 2003
Analysis
Sergio Palomares-Ruiz
November 17, 2008
16 4-MeV bins in the range [18,82] MeV
Nl = Number of events in bin l
Al = fraction of signal events
Bl = fraction of Michel electrons (positrons)
Cl = fraction of atmospheric electron (anti)neutrinos
P( )  K e
2


2

 90
 P( )d  0.9
0
Annihilations:
Sergio Palomares-Ruiz
November 17, 2008
We perform a similar Â2 analysis as that
done by SK to limit the flux of DSNB and we set
an upper bound on the DM annihilation cross section
SPR and S. Pascoli, SPR,
Phys.arXiv:0805.3367
Rev. D77:025025, 2008
Sergio Palomares-Ruiz
What if this is actually the case and
DM only annihilates into neutrinos?
November 17, 2008
C. Boehm, Y. Farzan, T. Hambye, SPR and S. Pascoli, Phys. Rev. D 77:043516, 2008
LENA: 50000 m3 scintillator after 10 years
Reactor BG
DSNB
Atmospheric BG
SPR and S. Pascoli, Phys. Rev. D77:025025, 2008
Decays:
Sergio Palomares-Ruiz
November 17, 2008
Using SK data from DSNB search:
Detailed analysis of background and energy resolution
 
GeV
o10
30
E

10
Ge
E
o
30
E

10
Ge
 4
SPR, Phys. Lett. B665:50, 2008
New model-independent bound
from CMB and SN observations
For γ-line limits:
Model-independent bound
from CMB observations
Y. Gong and X. Chen,
Phys. Rev. D77:103511, 2008
H. Yuksel and M. Kistler,
Phys. Rev. D78:023502, 2008
K. Ichiki, M. Oguri and K. Takahashi,
Phys. Rev. Lett. 93:071302, 2004
Sergio Palomares-Ruiz
A few words on PAMELA
November 17, 2008
O. Adriani et al., arXiv:0810.4994
O. Adriani et al., arXiv:0810.4995
Annihilations: need of large boost factors
Sub-structure
Sommerfeld enhancement
Non-thermal production
M. Cirelli, M. Kadastik, M. Raidal and A. Strumia,
arXiv:0809.2409
Decays: no need of boost factors -> “short” lifetime
d dk
d ann  3 10 26 cm 3 / s  0.3 GeV/cm 3  m  10 26 s 



 10


  
dE
dE 


100
GeV


0



  
Sergio Palomares-Ruiz
November 17, 2008
Conclusions
• Neutrino detectors can test DM properties
• Searches for neutrinos from DM annihilations/decays in the
galactic halo could constitute powerful probes of DM
properties
• Neutrino detectors can set model-independent bounds on the
DM annihilation cross section and on the DM lifetime
• Difficult to distinguish annihilation/decay scenarios: use
angular information
• Future detectors (LENA) might be able to detect a signal from
DM annihilations/decay
Sergio Palomares-Ruiz
November 17, 2008
The world is full of obvious things
which nobody by any chance ever observes
When you have eliminated
all which is impossible,
then whatever remains,
however improbable,
must be the truth
Sherlock Holmes
Long arm looking for a fingerprint
trying to find the mystery clue
Bon Scott