New Limits on the Origin of Dark Matter

( -- Determining the identity of dark matter, the mysterious stuff thought to make up the vast majority of matter in the universe, is one of the most fundamental challenges facing modern physics. Through theory and experiment, scientists have been gradually determining what dark matter probably isn't composed of, and now recent results from one collaboration have ruled out another possibility.

The collaboration, representing seven institutions in the U.S. and Spain, is known as CoGeNT. Their work has shed light on the results of two large experiments designed to gather information about dark matter, DAMA (as in DArk MAtter) and its second-generation version, DAMA/LIBRA.

DAMA and DAMA/LIBRA are particle detectors buried within Italy's Gran Sasso mountain, located in the country's central Abruzzo region. Over the last ten years the detectors have recorded a yearly rise and fall in signal, which scientists guessed could be the result of Earth passing through a halo of weakly interacting massive particles (WIMPs), a class of theoretical particles that are a prime candidate for dark matter. The idea of a WIMP halo as the cause of the signal pattern is controversial, but physicists could come up with no other explanation.

Other dark-matter studies have ruled out the possibility that the signal is due to WIMPs, but the detectors used were not able to track very lightweight WIMPs nor could they investigate certain interactions between the WIMPs and the sodium-iodine nuclei in the detectors.

One of those interactions, those that depend on the "spin" of the detector nuclei—an intrinsic property, like electric charge—was ruled out by a collaboration known as COUPP (the Chicagoland Observatory for Underground Particle Physics), an underground detector based at Fermilab, near Chicago.

CoGeNT has now ruled out the case in which these interactions are do not depend on spin, effectively eliminating a standard WIMP halo as the cause of the DAMA/LIBRA signal modulation.

"Our detector is ideal for exploring the veracity of DAMA's claim of dark matter discovery," explained experiment spokesperson Juan Collar, a physicist at the University of Chicago, to "With it we may soon be able to reproduce or unambiguously refute their results, for more than just one type of particle candidate.

The detector is surrounded by a nested structure of passive and active shields, which act as other detecting media. Together they filter out background radiation so that it does not reach the core, which is a pure germanium crystal. The entire structure is slightly taller than an average-height person and about as wide. When a particle does reach the core, the energy it deposits is converted into a digital signal.

The spectrum of energy depositions obtained was compared with expected signals from a standard galactic WIMP halo, and they did not match.

"While the WIMP hypothesis now seems an unlikely explanation to the DAMA modulation, the DAMA collaboration has reminded us that dark matter candidates are numerous," says Collar. "The remaining controversy around the DAMA claim illustrates the point that detecting dark matter will be a very steep exercise for any single experiment in this field."

These results are described in the December 17, 2008, online edition of Physical Review Letters.

Citation: PRL 101, 251301 (2008)

Copyright 2008
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of

Explore further

Nobel Prize for Physics awarded to 3 scientists for their contribution to understanding of the evolution of the universe

Citation: New Limits on the Origin of Dark Matter (2009, January 27) retrieved 21 October 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Jan 27, 2009
It occurs to me that most of the visible matter - the glitzy, colorful stuff - is made up of powerfully interacting massive particles, or PIMPs.

Jan 27, 2009
Really strong attractions are what you are talking about. Show me your PIMP theory

Jan 27, 2009
LOL haha, thales that was lame.

Jan 28, 2009
" ... scientists guessed ...". Since when has science become guesswork? I bet a PIMP against a WIMP anytime. I "guess" it could have been the Flying Spaghetti Monster and find just as much (non)evidence as the tosh in this report.
lol@Thales ...

Jan 28, 2009
Dark Matter is a myth. Read John Moffatt's theory of gravity it makes a lot of sense and is simple. It does away with the need for dark matter and explains why the universe is expanding at it's present rate. I think that he is on the right track.

Jan 28, 2009
" ... scientists guessed ...". Since when has science become guesswork? I bet a PIMP against a WIMP anytime. I "guess" it could have been the Flying Spaghetti Monster and find just as much (non)evidence as the tosh in this report.
lol@Thales ...

Science IS guesswork. There is LITERALLY no such thing as a fact!!!! The only single fact in existence is...the fact is that there are none.

That's it.

Engineers are handed a big box of LIMITS to MAKE THINGS with ----but scientists are SUPPOSED to guess.

That is THEIR JOB!!


Get it straight.

Literal minded thinkers will be the death of us, dammit.

Jan 28, 2009
This whole dark matter thing seems fishy to me. The observatins don't match the theory. So they invent a new type of matter to match it?

Jan 28, 2009
"Literal minded thinkers will be the death of us, dammit."

Is that a fact?

Science requires evidence to support a hypothesis that then becomes theory. The theory is then required to be verified by independent sources. Anyone can make a guess, conjure up some far fetched idea like dark matter or wimps or gravity waves but its all just fantasy if theres no evidence, no detection, no testable or replicable experiments to support a claim.

Science is not about making unsubstantiated guesses as to what might be. Its about a reasoning process and not a matter of belief or faith.

This article was speculation and rightly deserves the label fiction.

... and thats a fact!

Jan 31, 2009
Did you ever wonder if it is possible to accelerate light?

Any wonder how mass was made?

The change grants the volume.

If you can find nothing in a test of particle collisions, then I suggest you have accelerated a particle past the speed of light... I'm sure you could get the right angle, so what would be the results in you finding? Does energy move faster than what we can see and observe?

How do you know that we are not inside a black hole? Are they not simply a critical mass of energy that has broken down the inter-atomic forces that hold atomic structures in form? That hold the very atom itself in volume... That holds the electrons apart from the protons, and that holds true the electron existence as one would describe it in magnetic theory... Basically crunching mass to the point where it approaches a finite volume. Well, as far close to finite as we can observe. Perhaps even forming time itself. You may be focusing on the appearances that black holes have mass %u2013 yet we are only viewing the extent to which light is drawn closely enough to be accelerated by force. I think that answers would be attained faster if we were to calculate the rate of change (from earth point of reference) that the universe volume is accelerating at. At least to what we can surmise. Obviously if light is actually a constant then the volume would be accelerating due to a vector radius changing the size of the sphere. But is that rate of change constant? Or is the formula actually observed to be integration and/or a derivative? If you can accurately theories this for me, then I may be able to adorn you some answers. I think that the question in of itself may beg of the answer. If you can devise the formula to the rate of change, then I can tell you the critical mass that results in a black holes formation. So much mass held together with so much more force that the universe (light) can not hold it apart within the relative argument of existence and functioning laws of our universe... I gave Hawkins his paradox years ago%u2026 the dude knows one - I still have seven more%u2026.

Jan 31, 2009
In good humor I would say that knowledge is the point of reference while intellect is the reason.

Kind regards - cheers - peace

Jan 31, 2009
so does John Moffitt suppose that time is the relative speed of light? Changing symmetry...

Feb 03, 2009
You can't argue with logic like that.

Feb 03, 2009
Dark matter exists in the minds of the creators. Those being unimaginative scientists whose approach to accounting is similar to the governmental one, if the books don't balance just print more money(matter).

Feb 13, 2009
dark matter is just a failure to understand the effects of gravity at long distances.

Feb 15, 2009
Bearing in mind that Einstein and all those who have followed him are totally unaware/in denial about "high spin atoms" that; do not form solids as they cannot bond with each other; when heated become lighter, as does the container they are in; and can also reside in molecules without changing the molecular properties; it is quite possible that the "missing" matter is not missing.
How come the ancients knew of four states of matter ( gas, liquid,the thing in between and solids) but Einstein only studied three?
Is this why his Unified Theory was never finished?

Feb 15, 2009
Hi there Razy,
As the real Zen Buddhists would say ... Everything is an illusion that is created by our minds and if enough people believe that it is so then it will be so; All that exists is energy, even a stone has more space within it than actual matter ( if one believes in matter that is )
And God said "Let there be light" and so it was. Then she said "Hmm I'm not so sure. Can I just have a look at the darkness again. It is so hard to decide...."

Feb 15, 2009
The only constant is that everything will change

Feb 22, 2009
So Gelvan, is that constant zero or one?

Nice one... what leads to infinite also leads to infinitely small, and that still be one for change... Motion is time, time is the speed of light, relative to nothing...

Or some other nothing... and maybe two or three more. Or was that one?

Feb 22, 2009
She also said imagine this: A rainbow made the earth, and the earth was given to us to behold... We see it, we let it see us, we interpret the changes.

Feb 22, 2009
And in one that function, for what would be that made in a dream, that be made to one, to behold many...

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more