Constraints on WIMPs as Dark Matter.

http://arxiv.org/abs/1108.3546
"The 95% confidence level upper limits on the annihilation cross
section range from about 1e-26 cm^3 s^-1 at 5 GeV to about 5e-23 cm^3
s^-1 at 1 TeV, depending on the dark matter annihilation final state.
For the first time, using gamma rays, we are able to rule out models
with the most generic cross section (~3e-26 cm^3 s^-1 for a purely s-
wave cross section), without assuming additional astrophysical or
particle physics boost factors."

http://arxiv.org/abs/1108.2914
"Dwarf spheroidal galaxies are known to be excellent targets for the
detection of annihilating dark matter. We present new limits on the
annihilation cross section of Weakly Interacting Massive Particles
(WIMPs) based on the joint analysis of eight Milky Way dwarfs using a
frequentist Neyman construction and Pass 7 data from the Fermi Gamma-
ray Space Telescope. We exclude generic WIMP candidates with mass less
than 27 GeV that reproduce the observed relic abundance. To within 98%
systematic uncertainties this lower limit can be as large as 80 GeV."

David A. Smith

On 08/22/2011 04:07 PM, dlzc wrote:
http://arxiv.org/abs/1108.3546
"The 95% confidence level upper limits on the annihilation cross
section range from about 1e-26 cm^3 s^-1 at 5 GeV to about 5e-23 cm^3
s^-1 at 1 TeV, depending on the dark matter annihilation final state.
For the first time, using gamma rays, we are able to rule out models
with the most generic cross section (~3e-26 cm^3 s^-1 for a purely s-
wave cross section), without assuming additional astrophysical or
particle physics boost factors."

http://arxiv.org/abs/1108.2914
"Dwarf spheroidal galaxies are known to be excellent targets for the
detection of annihilating dark matter. We present new limits on the
annihilation cross section of Weakly Interacting Massive Particles
(WIMPs) based on the joint analysis of eight Milky Way dwarfs using a
frequentist Neyman construction and Pass 7 data from the Fermi Gamma-
ray Space Telescope. We exclude generic WIMP candidates with mass less
than 27 GeV that reproduce the observed relic abundance. To within 98%
systematic uncertainties this lower limit can be as large as 80 GeV."

David A. Smith

So what exactly do these two studies mean? First one talks about a range
from 5 GeV to 1 TeV, while the second talks about a range from 27 GeV to
80 GeV.

Yousuf Khan

Dear Yousuf Khan:

On Aug 22, 10:32*pm, Yousuf Khan wrote:
On 08/22/2011 04:07 PM, dlzc wrote:

http://arxiv.org/abs/1108.3546
"The 95% confidence level upper limits on the annihilation
cross section range from about 1e-26 cm^3 s^-1 at 5 GeV
to about 5e-23 cm^3 s^-1 at 1 TeV, depending on the dark
matter annihilation final state. For the first time, using
gamma rays, we are able to rule out models with the most
generic cross section (~3e-26 cm^3 s^-1 for a purely s-
wave cross section), without assuming additional
astrophysical or particle physics boost factors."

http://arxiv.org/abs/1108.2914
"Dwarf spheroidal galaxies are known to be excellent
targets for the detection of annihilating dark matter. We
present new limits on the annihilation cross section of
Weakly Interacting Massive Particles (WIMPs) based
on the joint analysis of eight Milky Way dwarfs using a
frequentist Neyman construction and Pass 7 data from
the Fermi Gamma-ray Space Telescope. We exclude
generic WIMP candidates with mass less than 27 GeV
that reproduce the observed relic abundance. To within
98% systematic uncertainties this lower limit can be
as large as 80 GeV."

So what exactly do these two studies mean? First one
talks about a range from 5 GeV to 1 TeV, while the
second talks about a range from 27 GeV to 80 GeV.

Two slightly different methodologies, one with higher confidence over
a narrower range.

What they mean is:
- Dark Matter as WIMPS is co-incidentally co-flowing with each target
object, and/or
- Dark Matter is not energetic / massive WIMPs

You can only look for positive detections, and Dark Matter as any sort
of entirely non-interacting particle / fluid cannot give that.

David A. Smith

On 23/08/2011 11:20 AM, dlzc wrote:
Dear Yousuf Khan:

On Aug 22, 10:32 pm, Yousuf wrote:
So what exactly do these two studies mean? First one
talks about a range from 5 GeV to 1 TeV, while the
second talks about a range from 27 GeV to 80 GeV.

Two slightly different methodologies, one with higher confidence over
a narrower range.

What they mean is:
- Dark Matter as WIMPS is co-incidentally co-flowing with each target
object, and/or

The target objects being just normal virtual particle pairs in the vacuum?

- Dark Matter is not energetic / massive WIMPs

If one of the particles is 1 TeV, that would make it 60 times as massive
as a water molecule.

You can only look for positive detections, and Dark Matter as any sort
of entirely non-interacting particle / fluid cannot give that.

Okay, so how exactly could measuring these energy levels result in
discovering where the Dark Matter may lie? Would there be an excess of
signals at these energy levels? If the Dark Matter is non-interacting,
then how can there be any excess of signals?

Yousuf Khan

Dear Yousuf Khan:

On Aug 23, 10:31*pm, Yousuf Khan wrote:
On 23/08/2011 11:20 AM, dlzc wrote:
On Aug 22, 10:32 pm, Yousuf *wrote:
So what exactly do these two studies mean? First one
talks about a range from 5 GeV to 1 TeV, while the
second talks about a range from 27 GeV to 80 GeV.

Two slightly different methodologies, one with higher
confidence over a narrower range.

What they mean is:
- Dark Matter as WIMPS is co-incidentally co-flowing
with each target object, and/or

The target objects being just normal virtual particle pairs
in the vacuum?

The target objects are large collections of normal matter, namely
dwarf galaxies as described.

- Dark Matter is not energetic / massive WIMPs

If one of the particles is 1 TeV, that would make it 60 times
as massive as a water molecule.

There *were* looking for massive...

You can only look for positive detections, and Dark Matter
as any sort of entirely non-interacting particle / fluid cannot
give that.

.... and I should have said "only interacting via gravitation", not
"non-interacting".

Okay, so how exactly could measuring these energy
levels result in discovering where the Dark Matter may lie?

These observations cannot do anything other than to say "Dark Matter
as WIMPs is not here, Dark Matter as WIMPs is moving along with these
normal matter collections, or Dark Matter does not interact with
normal matter to produce energetic reactions, as would be required to
be WIMPs".

Would there be an excess of signals at these energy levels?

If DM was WIMPs, and as massive as "expected" for WIMPs, yes.

If the Dark Matter is non-interacting, then how can there
be any excess of signals?

Correct, it can't. It is a matter of looking under the streetlight
for something you lost in the Dark. They have just made sure that
WIMPs (something in the fringes of the streetlight) are constrained to
the energy level of proton masses or smaller, which makes neutrinos
(or a bit heavier) and/or classical Dark Matter the only viable
candidates.

Its just another mile post on the road to narrowing down what DM is...
by eliminating what it isn't.

David A. Smith