
China’s dark matter space probe detects tantalizing signal - yuvalr1
http://www.sciencemag.org/news/2017/11/china-s-dark-matter-space-probe-detects-tantalizing-signal
======
fspeech
For those interested the preprint is at
[https://arxiv.org/pdf/1711.10981.pdf](https://arxiv.org/pdf/1711.10981.pdf)
The satellite carries a very large BGO calorimeter
[https://arxiv.org/abs/1406.3886](https://arxiv.org/abs/1406.3886)

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nigwil_
I noticed this paragraph about code to do this analysis:

    
    
      "Code availability. The numerical code has been developed
      with a dedicated application to the DAMPE data analysis. Due
      to the uniqueness of the DAMPE design and the complexity in-
      volved in the data analysis, the software package has limited 
      application to the relevant community. We have opted not to
      make the code public."
    

I'm just an IT guy, and not familiar with how disciplines distribute source-
code for this type of analysis, but is this approach common? what does
"...limited application" mean here and why not release the code?

~~~
lsh
I'm a tech, not an academic, but I see it as part of the broader problem of
science reproducibility. Software plays a huge huge part in modern science
publishing and, in the case of data derived using proprietary software, it's
expected we just trust the results - that the software is infallible.

The comment "We have opted not to make the code public." really gets my goat,
but is probably less because they sampled community opinion and found it
wanting but more because it's just plain inconvenient or unknown how to
publish software.

Authors are not actively discouraged from publishing details about the
software used (in journals in general) or including copies in the
supplementing files, but the process typically has the editors (who guide the
authors through the submission process) paring back the submission to just bog
standard and familiar media types: image, audio, video, pdf, etc that are
known quantities and can be nicely formatted in the final pdf.

My small contribution to combating this has been encouraging our editors at
eLife to be alert to authors using bespoke or modified software and capturing
that software at a specific revision at the time of publication
([https://github.com/elifesciences-
publications](https://github.com/elifesciences-publications)) and making sure
it meets some basic criteria, like being openly licensed.

I'm hoping this effort will help resist general entropy and bit-rot, software
moving on or getting lost, licence changes and the overall mandate of eLife to
improve science publishing, which means reproducible results and software
amenable to audit.

------
essive
Hmmmm...scientists are still debating whether the signal is dark matter or
pulsar output (high energies create electron-positron pairs). I see this
recent Chinese paper debating if DAMPE can even distinguish dark matter
positron remnants or pulsars - Wang et al. (2017) say this - "For the pulsar
case, the latest Fermi-LAT anisotropy limits have also been taken into
account. Our results show that the cases of DM annihilations to τ+τ− and all
charged leptons are difficult to be distinguished from the pulsar cases by the
current experiments and DAMPE"

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piotrkaminski
> In its first 530 days of scientific observations, DAMPE detected 1.5 million
> cosmic ray electrons and positrons

> "we now expect it to last 5 years"

> That will allow the satellite to record more than 10 billion cosmic ray
> events.

Assuming DAMPE continues detecting cosmic ray events at its current rate, I
think the total number after 5 years would be a bit over 5 million. That's a
few magnitudes off of 10 billion... Math fail, or do I misunderstand
something?

1.5m / 530d * 5y * 365d/y = 5.165m

~~~
e2e8
From the paper: During these ∼530 days of operation, DAMPE has recorded more
than 2.8 billion cosmic ray events, including ∼ 1.5 million CREs above 25 GeV.

~~~
piotrkaminski
Ah, makes sense now -- should've gone to the source instead of trusting the
article to summarize all numbers. Thanks!

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AmericanOP
Have we ever observed annihilation? Its supposed to emit a ton of energy,
right?

~~~
aisofteng
Matter-antimatter annihilation? Yes, absolutely. As one starting point, see:
[https://en.wikipedia.org/wiki/Electron–positron_annihilation](https://en.wikipedia.org/wiki/Electron–positron_annihilation)

