Has PAMELA Already Seen Dark Matter?

August 25, 2009 by Miranda Marquit, Phys.org weblog

PAMELA is launched onboard a Resurs-DK1 Russian satellite by a Soyuz rocket in June 2006.
(PhysOrg.com) -- Back in 2006, PAMELA (a Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) was launched with the purpose of detecting cosmic radiation and looking for clues pointing to dark matter. And now it's possible that PAMELA might have already spotted dark matter.

Earlier this year, PAMELA sent data about high energy positrons -- a higher presence of them than originally expected. Speculation is that these positrons might have been generated by annihilations. Annihilations are collisions between particles that result in high amounts of energy.

Philipp Mertsch, a researcher at Oxford University in England, is working on figuring out how to detect dark matter, using information from PAMELA. He was interviewed by the Oxford Science Blog about dark matter, and how to test if these positrons represent the results of dark matter:

If dark matter is made of new elementary particles (and antiparticles) created in the then these will occasionally annihilate with each other in the dense environ of our Galaxy. Most of the energy released like this goes into or gamma-rays but a small fraction is released as energetic positrons into the cosmic radiation.

Subir Sarkar, who is also working on this project, goes on to point out that one of the problems is distinguishing between positrons and protons. The team at Oxford has devised a test to determine the source of the protons, and Sarkar offers this on the Oxford Science Blog:

Measuring the ratio of the flux of nuclei compared to carbon nuclei can therefore discriminate between the dark matter and pulsar source models on the one hand and the nearby cosmic ray accelerator model on the other hand.

While this ratio is being measured right now, there is a larger experiment slated to run next year, so the test can be better carried out. It will be interesting to see what comes back. Dark matter is of great interest to astrophysicists who contend that most matter in the universe is actually dark matter. Additionally, the presence of dark matter, and knowing what it is composed of, could answer questions about how our universe came into being -- and how it is evolving.

© 2009 PhysOrg.com

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2.2 / 5 (10) Aug 25, 2009
These positrons may originate from distant pulsars, too.

But I'm rather convenient with the dark matter origin of most of antimatter observed, as it supports AWT well.

not rated yet Aug 25, 2009
Well if the gamma is 511GeV, then yes, it was caused by annihilation, otherwise NO.
3.4 / 5 (5) Aug 25, 2009
PAMELA found an excess of positrons from 10%u2013100 GeV range in the cosmic ray, but value 511MeV (not GeV) is relevant only for anihilation of electrons and positrons at rest. High speed collisions are producing gamma rays of arbitrary energy scale.
3.4 / 5 (5) Aug 26, 2009
Has PAMELA Already Seen Dark Matter?

No, PAMELA has seen positrons and no amount of theoretical spin can turn them into dark matter.
1 / 5 (2) Aug 26, 2009

Measuring the ratio of the flux of boron nuclei compared to carbon nuclei can therefore discriminate between the dark matter and pulsar source models on the one hand and the nearby cosmic ray accelerator model on the other hand.

That discrimination is all well and good in itself of course, but this is a confession that the article's claims of dark matter detections this way is an oversell. And indeed, the mundane hypothesis is that pulsar sources explains the observations, and this would be a good test of that.


Aether was rejected 1887 with Michelson's and Morley's experiments.

"no amount of theoretical spin can turn them into dark matter"

But these things are exactly what theory and experiments are good for, obtaining natural mechanisms explaining observations. And _that_ knowledge is much older than relativity even.
Aug 27, 2009
This comment has been removed by a moderator.
3 / 5 (1) Sep 01, 2009
" Aether was rejected 1887 with Michelson's and Morley's experiments..."

It was only the rigid Aether model that M+M experiments contradicted. They regarded that experiment and their and others later ones as PROVING that a fluid aether reference frame for EM waves was correct. Superfluid it seems actually. Hence transverse EM waves.

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