Tuesday, August 12, 2014

Controversy about the \(3.5\keV\) line

A year ago, we would sometimes watch the disagreement of experimental astrophysicists concerning the existence of sub-\(10\)-\({\rm GeV}\) dark matter particles which was suggested by DAMA, CoGENT, CDMS Silicon, and others. LUX finally showed that those hints had to be due to some overlooked boring phenomenon because even with the superior sensitivity of the South Dakota detector, the graphs are as clean as you can get.

Someone seemed to be sending X-rays from the Central Milky Way.

Another potential intriguing signal has become questionable. Jester would write about the neutrino dark matter seen in the \(3.55\keV\) X-ray signals. The same Jester now wrote a blog post titled
X-ray bananas
about two new papers, a positive one and a negative one.

Jester is faithful to his personality which is why he only discusses the negative one. It's a paper with the "bananas" in the title – this word has appeared in the physics titles before.

The positive paper was published today and it does argue that there is a \(3.55\keV\) line in the Milky Way center. The somewhat older negative paper claims that
  1. some upper bounds imply that the sterile neutrinos in the Milky Way center may be ruled out
  2. there is no signal, anyway.
The first claim could be considered interesting but harmless because many people would think that axion, axinos, and moduli are more motivated explanations of such a potentially new line in the spectrum.

Concerning the second negative and more powerful claim, they support the worries of some of us – that there are way too many boring spectral lines around \(3.5\keV\) and two of them emitted by potassium may fully account for the "signal", up to 1-sigma errors.

Aside from potassium, these authors have borrowed another powerful weapon in their effort to exterminate the germs of the dark matter excitement: chlorine. (I pray that the Kiev junta won't do the same thing in Donetsk.)

I was personally betting that this \(3.5\keV\) signal has always been due to some mundane spectral lines and other effects because these lines are dense and hide lots of potential for minor errors and misunderstandings. But it's true that I am in no way certain in one way or another and we are probably going to see many papers on both sides before the situation gets clear.


  1. Quite sad! That it should be TRF to break the news after 6 weeks shows how loosely knit together the skeptical blogosphere is. By the way, does anybody know whatever happened to Dr. Murry Salby?

  2. "...Nigel Calder is no longer with us..."

    You are wrong, Nigel Calder will be always with us.

  3. This is off-topic. But I saw a recent QM experiment called "The Cheshire Cat" where a particle is separated from its properties. My rudimentary knowledge of QM tells me this makes no sense. One of the people involved did the pigeon-hole experiment so I am guessing he's exploiting the same false "loophole" to get this latest result?

  4. Six tests of vacuum chiral anisotropy are chemical. A non-zero output resolves dark matter, baryogenesis; parity violations, symmetry breakings, chiral anomalies, Chern-Simons repair of Einstein-Hilbert action. One day in a microwave spectrometer detects 10(-15) difference/average divergence. "This is not the answer we are seeking."

    In contrast, we see the finest minds on the planet vigorously engaged in snark hunts. They emulate NASA (we only fly what has flown) and economics (heteroskedasticity - one more parameter, one more decimal place is success). Chemistry engages windmills: classical fluxional vs. quantum 2-norbornyl cation,


    (they didn't call it "bullvalene" because they believed it)

    but you guys are the galactic champions of perseverative empirical smartlessness. Look not under the streetlight.