Dark Matter Damping

There is an interesting discussion over at Sarah’s blog, about astronomers being driven by ambition and greed just like everybody else. I remember this concept shocking Donald Pettie, the ex Chief Engineer at ROE, who moved there from Ferranti back in the eighties. He thought academics would be gentle, polite people. In some ways this was true, but he told me that he soon learned that the average astronomer would be prepared to sell his grandmother for an extra night on a big telescope.

There was something of an unseemly stampede last year when the ATIC results were announced – a claim of a hump in the cosmic ray electron energy spectrum, that could be a feature caused by the decay of dark matter particles. Gold !!!!!!! At a conference where the pre-publication results were presented, someone apparently photographed the screen, measured the points, and rushed a paper out. Of course this was only one of a gazillion papers with different interpretations. But now Fermi has made this all seem a bit daft : a paper just out in Phys Rev Lett has made an absolutely exquisite measurement of the CR energy spectrum from ten to a thousand GeV, which slides neatly underneath the ATIC data. Bump not there. See below.

Cosmic Ray electron energy spectrum measured by Fermi satellite

Cosmic Ray electron energy spectrum measured by Fermi satellite

Well this result has already caused a splash in the popular press and astroblogs (here is Sean Carrol’s take), but I had it in mind because I just attended a SLAC seminar explaining the result, given by Luca Patronico. The particle physicists are still seeing the glitter of gold in the river; the beautiful Fermi data disagree not only with the ATIC hump, but also with the “conventional diffusive model” … there are already papers out on ArXiv with revised DM fits…

However I am glad to report that the astronomers in the audience were somewhat saner. Not only is it possible that nearby pulsars could produce this “excess”,  at least one older wiser head said “errr… you aren’t taking that conventional diffusive model too seriously are you ? We don’t really understand the transport of cosmic rays through the ISM in that level of detail. Its kinda tricky. I can give you any curve you want”.

Maybe its relevant that the person who said this is already mature and respected … no need to grab at every chance of fame….

5 Responses to Dark Matter Damping

  1. “You’d look pretty simple too, Fred, at a distance
    of 10 parsecs” someone once said to Fred Hoyle.
    Models are usually simpler than reality.

    Aggressive? Certainly. When I was at Jodrell Bank,
    I heard stories about people visiting from the States
    saying “How can you leave your notebooks open in the
    library? Won’t someone steal your stuff?”

    In an up-or-out world, one has to survive somehow,
    and ambition and greed is the route some people take.

    I once presented a poster at a conference and put
    it up on my web pages. Looking through the access
    logs, I could see, in addition to the normal hits,
    many from one address. Finger showed only one user
    logged in, so it was clear who it was. A short time
    later, a colleague alerted me to the fact that the
    abstract of a preprint he was reading sounded
    familiar. Sure enough, some of it was almost
    word-for-word stolen from me.

    I later learned that I was far from the only victim;
    some others might not even have noticed.

    I managed to get the corresponding refereed-journal
    paper published and prevent one from the “competition”
    from being published. But I am no longer paid to
    do astronomy and the competition is. Go figure.

    As Groucho Marx said, sincerity is everything. Once
    you can fake that, you’ve got it made.

  2. This is fun stuff. I collected some quotes and reported from a seminar downstairs at the Stockholm Physics department last week (googletranslation here).

    Our friends in the DM crowd are clearly falling over themselves to publish papers about these things. Are the pulsar people and the diffusive model people on the ball enough? Do they have almost-finished papers ready to submit almost before the results come out? It would be a shame if they missed out on the fun.

  3. Robert Johnson says:

    A correction regarding the history: The incident with the digital camera recording a plot shown in a conference was concerned with the Pamela measurement of the ratio of positrons to electrons, not the ATIC measurement. Pamela is an orbiting spectrometer, while ATIC is a balloon experiment. Also, Luca’s last name is Latronico.

  4. andyxl says:

    Robert – oops and double oops. Many thanks for your corrections ! Error-1 was laziness (didn’t check story…) and error-2 was dumb typo. Luca’s talk was by the way very good. The PAMELA result now looks more interesting in a way. I hear folk say that it can be explained by pulsars, but as far as I know you can’t explain it away with cosmic ray transport.

  5. […] Why bother selling your grandmother… […]

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