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`Irony` actually does mean `metal like`...

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`Irony` actually does mean `metal like`...

Interesting

Hum,
yeah,
if confirmed it'll be one of the most important discoveries this year, (with implications for dark matter searches).

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`Irony` actually does mean `metal like`...

Axions are one candidate for dark matter, but have never been detected before. This very short lifetime seems to pose a problem for the dark matter axion, though; how can an entity with such a short lifetime be the dominant form of mass in the universe?

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Orion's Arm . The Starlark . Voices: Future Tense- Novella Contest Issue! . OA Flickr set

I seem to recall several types of axions-- this would not be the one directly relevant to dark matter if it couples to electrons, especially that quickly, in my limited understanding of particle physics.

I'll take a look at the APS site as well as the PDG to see what, if anything they have to say. I tend to distrust press releases on principle as they dumb down and overstate results. Unfortunately I can't download the journal article on my home computer. It may require a subscription but I'll try at work tomorrow. The article will contain the info press releases don't such as the technique used, the cuts on the data, any systematics, etc. Stand by to stand by.

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"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee

This isn't right. This isn't even wrong. - Wolfgang Pauli

I for one will be very curious to see your analysis of this matter.

Count me as interested but skeptical. As others above, press releases aren't my favorite way to see news about major finds.

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Forming opinions as we speak

I've downloaded the paper. They allow free access for papers published in the last 30 days (registration required though). For reference here is the PDG listing and tutorial on axions. I'm working my way through it as well. The theoretical part dates from the late 90's, but the experimental summary was updated in 2003.

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"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee

This isn't right. This isn't even wrong. - Wolfgang Pauli

A couple of quick comments. First, there seems to be nothing obviously wrong with the experiment or the reconstruction. The authors look at the invariant mass spectrum of e+e- pairs produced by heavy ion (lead in this case) impacts in a film emulsion. The interest in the region below 100 MeV is because any particle found there would have to be new. The pions have masses around 135 MeV and are the lightest known particles after the electron.

That being said, the evidence is less convincing than the press release would have one believe. The authors mention that an axion search is the primary reason for the experiment, but stop short of saying that the two mass peaks they see in their invariant mass plot (at 7 and 19 MeV) are indisputably axions. Even the paper's title reflects this caution. The phrase "Search for..." in a paper's title usually means that the experiment did not find the effect in question or that the authors are being cautious in their assessment of the result.

The invariant mass plot does show two fairly large peaks at the masses mentioned. However, this alone is not proof that there is something there. I was in my own fair share of "bump hunts" during my grad work and saw many similarly "significant" peaks vanish when new data was analyzed. It will be interesting to see what follow on experiments show. More to come as I read on.

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"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee

This isn't right. This isn't even wrong. - Wolfgang Pauli

The Muon is lighter, but I take your point and agree.

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Forming opinions as we speak

Oops, I meant to say lightest meson. In any case, the mass difference between mu and pi isn't that great. Also, since the muon doesn't decay to e+e- it isn't a possible background to the signature they are looking for.

__________________
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee

This isn't right. This isn't even wrong. - Wolfgang Pauli

Can you comment on any ramifications for dark matter if this result holds up, or does evidence for this type of axion not relate to the potential dark matter axions?

Hum,
It would mean that the axion is not a direct candidate for darkmatter. However, if it is shown to exist then the darkmatter search could be directed to more exotic partners which could possible exist; it would be a longer lived wimpy superpartner with a tiny mass that may need to be found.

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`Irony` actually does mean `metal like`...

Here are two recent articles in which a claimed discovery of axions is reported. The results will be published in British Journal of Physics G: Nuclear and Particle Physics next month. However, the articles report that the axion has a very short lifetime. So, if it has such a short lifetime, then how could it be a part of the Universe's dark matter?

Cousin Of Higgs Boson Detected
http://www.scienceagogo.com/news/200...runc_sys.shtml

A scientist finally proves existence of elusive axion
"Using a visual target/detector, a University of Buffalo researcher has revealed the existence of the axion, a tiny particle with no charge, a very low mass and a lifetime much shorter than a nanosecond." From:
http://news.sawf.org/Health/29483.aspx

Here's a citation for the paper:

P. L. Jain, G. Singh, Search for new particles decaying into electron pairs of mass below 100 MeV/c2, J. Phys. G: Nucl. Part. Phys., 34, 129-138, (2007); doi:10.1088/0954-3899/34/1/009

though a contributor's comment in Wikipedia under "Axion" is that the claim is not very strong.

Todd

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Todd (Bowie, MD, US, North America, Earth, Sol System, Vega region, Local Bubble, Orion arm, Milky Way Galaxy, Local Group, Virgo A Cluster, Virgo supercluster, the universe in which spock is clean shaven)

Quidquid latine dictum sit, altum sonatur.

personal page: http://blog.astrosketches.info

A high energy axion (interacting with other particles) apparently has a variety of decay modes available. However, a very low energy axion would not be able to decay by those modes, and so would be extremely stable. I don't know that it's the most viable choice, but it is a possibility, especially if it's actually been detected.

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Conserve energy. Commute with the Hamiltonian.

Threads merged - apologies for any confusion.

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Everything I need to know I learned through Googling.

Just to reiterate the point I made in post 11. The paper does not claim that they have found definitive evidence for axions. They have found something that might be an axion or might be a statistical fluctuation. Any time a paper's title includes the words "Search for..." it means that the authors either did not find the effect they were looking for or are hedging their bets. If this paper had been titled "Direct Evidence for Axion Production at 7 and 19 MeV/c2" then the statement that they have found the particle might be supportable. As it is, only the press releases (gag) show that level of confidence. The paper does not.

__________________
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee

This isn't right. This isn't even wrong. - Wolfgang Pauli

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Everything I need to know I learned through Googling.