Is this a purposeful play on words? The silent search is still silent even after 1.5 years. Hard for the DM advocates to swallow.

OK, time to teach you how to read (yet again *sigh*). You didn't even get to the third paragraph before making another one of your ultra-stupid posts.

Did you notice this sentence in the article?

That enables scientists to confidently eliminate many potential models for dark matter particles

or this

theoretical CANDIDATE

(emphasis mine)
or this

While the LUX experiment successfully eliminated a large swath of mass ranges and interaction-coupling strengths where WIMPs might exist

DM isn't one theory. It is a category for a whole host of theories. The label DM just descibes "that effect which we observe but cannot yet explain" (it doesn't even say the effect is necessarily cause by matter).

So unless you disagree with actual observation of the nigh sky you, too, are "DM advocate"

@BartV

A null result is still a result; but I wouldn't expect you to understand.

So what has been eliminated? And more important, what remains?

So what has been eliminated? And more important, what remains?

From the abstract of this
https://arxiv.org...211.3788

The goal of the LUX detector is to clearly detect (or exclude) WIMPS with a spin independent cross section per nucleon of 2×10^−46 cm2

I.e. for WIMP theories stuff with a lower cross section remains.

Does anyone know if this is significantly below the neutrino/nucleon cross-section?

Does anyone know if this is significantly below the neutrino/nucleon cross-section?

Looks to be comparable but don't quote me – the Ultimate Neutrino Page has for the neutrino-nucleon elastic c.s.:
σ_νn→νn(E) ≈ 9.3E-48 m² (E_ν / 1 MeV)² = 9.3E-44 cm² (E_ν / 1 MeV)², and
σ_νρ→νρ(E) ≈ 6.0E-50 m² (E_ν / 1 MeV)² = 6.0E-46 cm² (E_ν / 1 MeV)².

". LUX's extreme sensitivity makes the team confident that if dark matter particles had interacted with the LUX's xenon target, the detector would almost certainly have seen it. That enables scientists to confidently eliminate many potential models for dark matter particles, offering critical guidance for the next generation of dark matter experiments."

How would one calibrate such a machine sans a priori knowledge of the signal that they were looking for? It seems to defy even the most basic of rigors. ", maintain a well-defined dark matter signature " ...", scientists were able to carefully quantify how the LUX detector responds to the signal expected to be produced from a WIMP collision.

What led them to expect that? Where did they get the idea that that's what this so called dark matter is?

"It would have been marvelous if the improved sensitivity had also delivered a clear dark matter signal. However, what we have observed is consistent with background alone.""

Well, it's really cool that they didn't just make stuff up, like the LIGO people did, but what would be a 'clear dark matter signal'? What would be this gravity producing...nothing?

""These careful background-reduction techniques and precision calibrations and modeling have enabled us to probe dark matter candidates that would produce signals of only a few events per century in a kilogram of xenon,"

And yet would have enough mass to warp the space time required to hold together a galaxy?

""We expect LZ to achieve 70 times the sensitivity of LUX. "
and if it reveals again nothing...then will you stop insisting that a question mark really is the answer to its own question?

mungoooo: you maybe don't understand how dark matter detection works. They're not looking for the gravitational interaction of these particles, that'd be impossible with our current technology. They're looking for one of these particles to 'bump into' an atom in the detector and in so doing cause something interesting to happen that produces light. For a wide variety of reasons, we don't expect that these particles 'bump into' normal matter very often, if at all. They pass through it like neutrinos do, but with even fewer reactions than neutrinos (they may, in fact, be some variety of neutrino as yet undiscovered).

But how often they bump into normal matter has no bearing whatsoever on their ability to attract gravitationally, so the point you raise in the second comment is meaningless. Interaction cross-section isn't necessarily related to the underlying mass of the particle.

Hi all. :)

I'd like to congratulate/thank the LUX team for their honest scientific efforts. Their Report of Null Results for their years long DM search experiment run is commendable both for its scrupulously objective efforts and its honest report of Null results. Refreshing after Bicep2 and LHC 'claims' to date

Alas, these results are not good news for DM enthusiasts. Many OTHER possible "candidates" have already been discounted in other efforts; leaving very little, if any at all, 'wiggle room' for DM 'optimists'.

Re the "interactivity' of whatever DM "candidate(s) are presumed to have with the matter:

If DM can interact with matter (even at low expected rate as per LUX scenario), then our night sky across cosmological distances should be swamped with radiation from such interactions because of the HUMONGOUS QUANTITY of ORDINARY MATTER recently increasingly being discovered distributed across billions of light years of (previously assumed) 'empty' space!

Cheers. :)

swordsman wrote, "They successfully discovered nothing! I can easily do that at a much lower cost."

I really don't understand why so many science deniers bother to visit this site. They are unable to grasp even the most elementary principles of scientific investigation.

A null dark matter detection from a carefully-designed experiment is not equivalent to a null dark matter detection from pooping in your hands. The first helps to rule out some, not all, candidate explanations for dark matter effects seen in cosmological observations. The second just gets your hands dirty, though it is undeniably cheaper.

The new headline should read:

IT HAS BEEN DISCOVERED THAT MOST OF THE UNIVERSE IS NOT MISSING

2×10^−46 cm2

Wow, that's like 8 orders of magnitude smaller than a neutrino.

On edit But then I saw:

Looks to be comparable but don't quote me – the Ultimate Neutrino Page has for the neutrino-nucleon elastic c.s.:
σ_νn→νn(E) ≈ 9.3E-48 m² (E_ν / 1 MeV)² = 9.3E-44 cm² (E_ν / 1 MeV)², and
σ_νρ→νρ(E) ≈ 6.0E-50 m² (E_ν / 1 MeV)² = 6.0E-46 cm² (E_ν / 1 MeV)².

Hmmmm. OK. Maybe not so much smaller.

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How would one calibrate such a machine sans a priori knowledge of the signal that they were looking for?

You check the background noise and see if all the signals you get can be explained by known processes.

They successfully discovered nothing! I can easily do that at a much lower cost.

No you can't. the trivial difference is:
They now KNOW that there is nothing in that energy range, whereas you could merely CLAIM that there is nothing within that energy range.

It's the difference between looking both ways and seeing that there are no cars coming
and
shutting your eyes, claiming that no cars are coming, and walking into the street.

One of those is sensible (and good science!)...the other is not.

wkingmilw wrote, "No discussion of the recent hypothesis that dark matter consists of middle weight black holes surrounding galaxies. Oh well."

There isn't much new to discuss. WIMPs aren't ruled out; their possible characteristics have just been narrowed. Meanwhile physicists don't have a good theory handy to suggest why middle-weight black holes could exist in the numbers and locations required to account for observed gravitational effects. There would have to be a *lot* of them. All of them dark. No observable eating allowed. Not ruled out either, but it's looking like a stretch.

Perhaps just as likely are some new and exotic kind of singularity, maybe stuff produced during the Big Bang. Cosmic strings, or something. Who knows? We need observations.

That's what this article is about. Physicists are looking. They haven't found answers yet.

The first helps to rule out some, not all, candidate explanations for dark matter effects seen in cosmological observations.

There are no DM effects seen in cosmological observations. It's all about a generation of aging Trekkies such as yourself, who have signed onto absolute foolishness & won't give it up since zany Zwicky concocted this slop-trough of cosmological swill in the 1930's against the advice of none other than Einstein himself.

You who has never worked as a science professional, are all into calling others "science deniers" just because your Trekkie dreams are beyond fulfillment. You sign onto narratives that imply Gravitational Lensing cannot occur anywhere in the Universe were it not for the presence of your favorite Cosmic Fairy Dust.

You're the "denier" when you cannot accept the fact that observations prove that the greatest gravitational effects are always found near giant Elliptical galaxy clusters, just where one would expect to see such effects.

That's what this article is about. Physicists are looking. They haven't found answers yet.

The article clearly states they have in fact "found answers". Did you even read it? It was clearly stated using the best detection instrumentation & data analyses that DM doesn't exist......here I'll quote it from the article because you are simply too lazy to read it:

LUX's sensitivity far exceeded the goals for the project, collaboration scientists said, but yielded no trace of a dark matter particle. LUX's extreme sensitivity makes the team confident that if dark matter particles had interacted with the LUX's xenon target, the detector would almost certainly have seen it.

There, get it? Probably not, you're just too much of a "science denier" incapable of a basic comprehension of nuclear physics.

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One wonders if this is the wrong path.
I have always subscribed to the dark matter theory but I think we may be wrong. Back to the drawing board. Matter, Anti-matter, and....mmm...two more quadrants on the black board....
Watching with anticipation. It is a most interesting time to live.

One wonders if this is the wrong path.
I have always subscribed to the dark matter theory but I think we may be wrong. Back to the drawing board. Matter, Anti-matter, and....mmm...two more quadrants on the black board....
Watching with anticipation. It is a most interesting time to live.