Friday, 20 February 2015

Friday wrap-up: dark matter direct detection in Australia, ICARUS vs MiniBooNE...

This week I have been at the CoEPP Annual Workshop on Australia's exclamation point. Highlights have included new results on the CKM unitarity triangle (Pesantez/Kandinsky) and the art installation about viXra. But actually, perhaps the most exciting thing is the update on the southern hemisphere underground lab, which is my first point...

  • The possibility of a direct dark matter detection experiment in Australia is increasing! The Victorian government has pledged $1.75 million to Stage 1 of the Stawell Underground Physics Laboratory and is seeking matching funds from the Commonwealth. This comes after a three-day workshop near Stawell (a few hours from Melbourne) in October last year with INFN representatives to discuss the possibility of collaborative research. The response from the Stawell community has been welcoming.

    In Hobart we heard an update on geological backgrounds. In short: neutron flux okay, gamma flux okay, radon flux high but manageable with surface air / adsorption on activated carbon / shielding. All good news.

    A detector in the southern hemisphere has the capacity to settle the case for the DAMA/LIBRA annual modulation signal. If the DAMA/LIBRA signal is real and originates from Earth's traverse through the dark matter halo, then the signal should not change for a similar experiment in the southern hemisphere. If the signal is spurious, due to some local Gran Sasso background or an unaccounted seasonal effect, then the signal will disappear or swap phase. A diurnal modulation signal might even be observed if dark matter is captured within the Earth. Any result would be an interesting result, and a new generation twin experiment would be particularly interesting.

    Professors Elisabetta Barberio and Geoff Taylor appeared on 936 ABC Radio Hobart and talked about it.
  • Related is a Wall Street Journal article about direct detection at Gran Sasso, specifically the Darkside-50 experiment. It includes a two minute video. 
  • ICARUS has updated and revised their comparison to the MiniBooNE $\nu_\mu$-$\nu_e$ oscillation anomaly, still suggesting an "unexplained nature or an otherwise instrumental effect for the MiniBooNE low energy event excess." The paper is worth reading if only for the maligning undertones... ICARUS already presented their results in July 2013 which appeared to rule out MiniBooNE at >99% CL:


    MiniBooNE posted a critical reply which "explains and corrects the mistaken analysis published by the ICARUS collaboration." The confusion seems to be in the translation between the reconstructed energy $E^{QE}_\nu$ and $E_{True}$. Let me quote an excerpt from the new ICARUS paper to give you a feel for their thoughts on the issue:

    It appears that the reconstructed energy is affected by a huge non-Gaussian smearing compared with the true neutrino energy, as clearly stated in [the MiniBooNE reply] (see Figure 2), in contrast with the much better 11% resolution on $\nu_e$ event energy quoted in a previous paper. This difference between $E_{True}$ and $E^{QE}_\nu$, for which MiniBooNE gave a quite elliptical explanation, is the major cause of the problem in using the L/E (or E/L) to compare data with expectations...

    They make two further remarks. First they argue that the MiniBooNE reply implies that MiniBooNE's own results were represented in a misleading way in the original paper, by being directly compared to LSND data. Second they point out that the MiniBooNE quoted errors are inconsistent from paper to paper, and they even have a plot comparing the errors to make the point.

    Anyway, upon updating the comparison, the MiniBooNE anomaly appears excluded at 90% CL but no longer at 99% CL.
  • LHC restart is expected in the last week of March:
  • The LHC PR machine has really started to gear up. Checking the In the News section at Interactions.org I count 26 news articles in the last week. It's the usual sell: the big bang, Higgs, SUSY, dark matter, and baryogenesis.
  • Old news, but I just learned that since the end of September last year you can search for papers in inspire by just copy-pasting a reference from a paper and using: find rawref "..." . That will save us a bit of time.
  • Here is a discussion with George Efstathiou (Kavli Institute, Planck) on Planck and inflation, quantum gravity, younger first stars, dark matter, primordial gravitational waves...
  • Natalie Wolchover at Quanta magazine always produces well-written and well-balanced articles (even Luboš agrees), and has delivered another one, this time on string theory; the byline asks, "Researchers are demonstrating that, in certain contexts, string theory is the only consistent theory of quantum gravity. Might this make it true?"
  • On the topic of Frank Wilczek, he has launched a mysterious web site for "Wolfcub Vision Inc".
  • On the arXiv now are two papers on the science, mathematics, and computation behind the black hole and wormhole visualisations in "\emph{Interstellar}".
  • It appears that Lisa Randall will be releasing a book "Dark Matter and the Dinosaurs" at the end of October this year. If you're wondering about the connection, Randall has an arXiv paper which links comet impacts to periodic transits of the Oort cloud through the galactic disk, hypothesised to align with a dark matter disk (if some component of dark matter is dissipative). Actually, The Economist picked up this story yesterday, though there's no mention of Randall. 
  • In video media...
  • The Pale Blue Dot photograph taken by Voyager 1 is 25 years old. Read the famous reflections by Sagan here. Voyager 1 entered interstellar space in mid-2012; it's still sending back data, but by 2030 will be unable to power any instrument. Click here to see where it is now.
  • Lastly, images from space...
    • Mysterious plumes are erupting on Mars (gif here) and as Dawn edges closer, the nature of the white spots on Ceres are still unknown: "We expected to be surprised; we did not expect to be this puzzled"; it will be in orbit on March 6. Are we living at the beginning of a sci-fi novel?

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