CANER UNAL
2010 CERN SUMMER STUDENT
PROJECT:Model-independent implications of the
electron, positron and anti-proton cosmic ray spectra
on properties of Dark Matter
1
Evidences for beyond SM
• Hierarchy problem (the huge difference between the weak and
Planck scales in the presence of the Higgs field)
• SM does not answer if there exists unification.
• No explanation about the dark matter and dark energy.
• It can be concluded that SM is the low-energy limit of a more
fundamental theory.(Some of the extensions of SM are
supersymmetry and extra-dimensions.)
2
Evidences for Dark Matter
• The most convincing and direct evidence for dark matter comes
from the observation of rotation curves of galaxies,namely the graph
of circular velocities of stars and gas as a function of their distance
from the galactic center.[1]
• The expected result:v(r) ~ R^-(1/2)
• A flat rotation curve implies that the mass continues to increase
linearly with radius.
3
•
In mechanics, the virial theorem provides a general equation relating the
average over time of the total kinetic energy, , of a stable system consisting
of N particles, bound by potential forces, with that of the total potential
energy.[2]
•
Swiss astrophysicist Fritz Zwicky applied the virial theorem to the Coma
cluster of galaxies and obtained evidence of unseen mass.He found that
there was about 400 times more estimated mass than was visually
observable. The gravity of the visible galaxies in the cluster would be far too
small for such fast orbits, so something extra was required. This is known
as the "missing mass problem". [2]
•
A gravitational lens is formed when the light from a very distant, bright
source (such as a quasar) is "bent" around a massive object (such as a
cluster of galaxies) between the source object and the observer. The
process is known as gravitational lensing.
•
Dark matter affects galaxy clusters as well. X-ray measurements of hot
intracluster gas correspond closely to Zwicky's observations of mass-to-light
ratios for large clusters of nearly 10 to 1.
4
Ωbh^2=0.024,
ΩMh^2=0.14
where h~0.71
5
EXPERIMENTS
1)DIRECT DETECTION
i)Scattering Classifications
ii)Experimental Efforts
2)INDIRECT DETECTION
i)Gamma-Ray Experiments
a)Ground-based telescopes
b)Space-based telescopes
ii)Neutrino Telescopes
iii)Positron and Antiproton Experiments
iv)Observations at Radio Wavelenghts
6
• Positron and Anti-proton Experiments
• Evidence for dark matter annihilations may also be observed inthe
spectra of cosmic positrons or anti-protons.However,unlike gammarays and neutrinos, these charged particles do not point to their
source due to the presence of galactic magnetic fields.
•
HEAT(High-Energy Antimatter Telescope)
(positron spectrum 1-30 Gev)
• BESS(Balloon borne Experiment Superconducting Solenoidal
Spectrometer)
(antiproton spectrum200 Mev-3 Gev)
• CAPRICE
(anti-protonup to 40 Gev)
The experimental sensitivity has increased dramatically.
7
• PAMELA(Payload for Antimatter Matter Exploration and Light nuclei
Astrophysics)
(Positron and anti-proton spectrum 50Mev-270Gev, 80Mev-190Gev)
• AMS(Alpha Magnetic Spectrometer)
An experiment to search in space for dark matter, missing matter &
antimatter on the international space station.
• Dark Matter evolution and cross-section explanation
• Among many possible cold DM candidates the most popular ones
are the stable weakly interacting massive particles(WIMPs).
8
•
MY PROJECT
•
The recently reported results by the PAMELA experiment shows a positron
fraction and flux anomally.This can be one of the most important indirect
evidences for the dark matter existence. (Moreover, no excess at the
antiproton flux)
•
Actually, the astrophysical background for less then 10 Gev is almost fitting
the observed data, but it is not enough to explain above 10 Gev.There has
to be another contribution coming from some source.
1)The model for standard astrophysical positrons is mistaken in some
way.If the source distribution in the galaxy is more complex, than such an
effect can be expected, however it is also expected that other cosmic-rays
are also effected from this complexity.
2)One single nearby source like neutron star.(Fermi have revealed that
pulsars are more numerous than expected)
(It is nearby since the energy loss of the elec., pos. is high)
3)The most exiting solution DARK MATTER EFFECT
9
DARK MATTER SM PARTICLES
In theory,The Dark Matter can produce SM particles with annihilation or
decay processes.Then it can contribute to the cosmic-ray flux.
Our model actually uses much higher value of cros-section with respect to the
estimated one by cosmology.
Actually, the dark matter signal is magnified with respect to the standard picture
in some way, by a factor ranging from 100-1000,
depending the model.
•
Actually, DM annihilations into SM leptons can fit well for almost any
masses higher than 60Gev.However, annihilations into quarks and Higgs
bosons are disfavored at low masses(because of soft positron
spectrum).Annihilations into gauge bosons work for both type of masses.
•
As I mentioned, the inclusion of the anti-proton changes the issue.Because
DM annihilations into gauge bosons, Higgs bosons or quarks porduce
antiprotons.However, for M_dm=> 10Tev is again consistent with the
PAMELA results.
10
•
A trouble is appeared when confronting this interpretation with channels
where corresponding excesses should appear such as cosmic antiprotons
and photons.
•
Actually, most of the models with this new physics expect annihilations or
decays of dark matter to produce ani-protons.
2 possible solutions:
1)The mass of the dark matter is so huge and annihilates dominantly into
W+W2)The dark matter annihilates to leptons mostly with no strong preference for
any DM mass.
In the 1st solution excess of anti-protons should appear in future higherenergy data.
In the 2nd solution, no hadrons are produced by this so-called ”leptohilic”
dark matter.
(Just note)One solution(not expected) a nearby clump of dark matter is
responsible .Then the anti-proton constraints are less stringent and the
ones coming from photon observations are totally avoided.However, it must
be so “bright” and close(closer than a few kiloparsecs).If such a clump does
exist , most probably Fermi has enough sensitivity to detect the associated
gamma-ray emission.
11
WHAT I HAVE DONE
• Fluxes
• Propagation
• Best Fit (by decreasing a concept similar to standard deviation)
• Samples
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.1
0.5
1.0
5.0
10.0
50.0
100.0
12
13
14