Friday wrap-up: IBL, SABRE...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics. Views are my own. Content very definitely skewed by my own leanings and by papers getting coverage, and it may not even be correct. It is a blog after all...

• ATLAS News had a wrap-up of the 900 GeV collisions performed last week. It was cool to see an event display with the insertable B-layer in action (the fourth and most inner layer of the pixel layers on the right insert):
  
  
  
  
  

• The Stawell Underground Physics Laboratory project here in Australia has received $1.75 mil from the federal government to match the State's contribution from earlier this year. The funding will go a significant way to constructing the clean room to host SABRE, the first southern hemisphere dark matter direct-detection experiment, the advantages of which I've mentioned earlier.

• If the dark matter distribution in M87 is spiked at the centre, then this arXiv preprint claims that thermal relic dark matter is ruled out for an unprecedented $m_{DM}\lesssim 100$ TeV! As well, an apparent excess at high energies can be explained by $\mathcal{O}(1-100)$ TeV dark matter. I wonder if this paper will become another galactic centre excess for hep-ph?

• The result has been on the arXiv for a while, but the CMS+LHCb $B_s (B^0)\to \mu^+\mu^-$ analysis was published in Nature, which I thought was interesting enough to note. As far as I can tell from a quick Inspire search, this is the first paper from the LHC Collaborations published in Nature. Note the 6 months from receipt to publication...

• A few very interesting articles this week:
• Nautilus: the story behind the OPERA superluminal neutrinos.
• Aeon: on the pervasiveness and apparent non-falsifiability of inflation.
• Scientific American: on physicists as philosophers.
• Quanta: ultra-high energy cosmic rays, the Oh-My-God particle, and an EeV+ hotspot in the sky.

• In video/audio media:
• New physics frontiers at the 13 TeV LHC from CERN. [3 minutes]
• A first video spot at Quanta Magazine: In Theory with David Kaplan (of Particle Fever fame) on what happens if you fall into a black hole. [2 minutes]
• And if you'd like to learn more about the man responsible for backing the foundation that supports Quanta Magazine in the first place (and for Chern-Simons forms, and for Renaissance Technologies), you should watch the very interesting interview with James Harris Simons at Numberphile. [19 minutes]
• Stephen Hawking on intelligence. [15 minute talk]
• Excellent video at SmarterEveryday on how the window shutters on the space station work. [8 minutes]

• Finally, updates on space missions: 
• New Horizons can now make out all of Pluto's known moons.
  
  
• The bright spots on Ceres we've been following now appear to be deposits of ice at the bottom of a crater.
  
  
  
  
  
  

Friday wrap-up: DM self-interactions, on-Z excess, AMS...

Wherein I list some (mostly) recent happenings, ramble a bit, and provide links, in an order roughly determined by importance and relevance to particle physics. Views are my own. Content very definitely skewed by my own leanings and by papers getting coverage, and it may not even be correct. It is a blog after all...

• This arXiv preprint answers my hanging question from a couple of weeks ago as to how the recent Abell 3827 (four-)galaxy cluster measurement is $10^4$ times more sensitive to dark matter self-interactions than the larger scale Bullet Cluster type measurement that hit the news in late March. The answer according to the authors: it isn't! The system is composed of four galaxies, each with a dark matter subhalo, infalling into a larger dark matter halo. The subhaloes are observed to have lagged behind after a long infall period, with the possible interpretation that the dark matter is experiencing some DM-DM drag force that the stars are not. The claim in this new preprint is that the Massey et al paper made the assumption that the stars and the associated DM subhalo develop completely independently. But clearly they are gravitationally bound! And this matters. When taken into account, it is clear that a much stronger dark matter self-interaction is necessary to explain the offsets of the subhaloes from the stars. They find a strength $\sigma/m_{DM}\sim 3 \text{ cm}^2\text{g}^{-1}$, in tension with the limit from the larger clusters (also from Massey et al...).

• On the ATLAS on-Z excess, I count already six articles dedicated to discussing/explaining it. In particular, this one points out that an explanation in terms of the simplified General Gauge Mediation model taken as a benchmark in the ATLAS paper is inconsistent with other measurements. As shown below, the white band preferred by the on-Z excess is disfavoured by a collection of other measurements.
  
  
  
  
  There are at least a-few-papers which claim that a decay chain more like $\tilde g \to q\bar{q}\tilde \chi_2^0 \to q\bar{q} Z \chi_1^0$ with a somewhat compressed spectra can go some way to explaining the excess while remaining consistent with other observations.

• On the AMS antiproton-proton "excess" there have been a few more preprints showing up on the arXiv. I took a quick look at this one, which does the sensible thing: notes that propagation models can fit the data fairly well, and that there is no unambiguous excess (though there are always some that see things another way...), nevertheless we can use these models along with the observations to bound the dark matter annihilation contribution at high energies -- which is the interesting physics after all!
  
  
  
  
  
  Above are the limits they derive on the annihilation cross-section into $b\bar{b}$ obtained assuming two different propagation models. What's interesting is that they compete with the Fermi dwarf spheroidal bounds for $m_{DM}\lesssim 100$ GeV, which is the region of interest for the galactic centre excess.

• The Stawell Underground Physics Laboratory project aiming at setting up the southern hemisphere's first dark matter direct detection experiment looks like it's really coming along (It even has a Wiki page now)! There was a stakeholder event in Stawell on Tuesday and some buzz from the CAASTRO group on twitter...
  
  

  You know it's getting official when there's a banner. pic.twitter.com/oXW0OPpdgX

  — Katie Mack (@AstroKatie) April 28, 2015

  Our search for #DarkMatter in a gold mine in Stawell is front page news! pic.twitter.com/gonnTz2YDs

  — Alan Duffy (@astroduff) April 28, 2015

• Ellis, Gaillard, and Nanopoulos have uploaded "An Updated Historical Profile of the Higgs Boson" to the arXiv.

• CRAYFIS won the Webby Award for Mobile Sites & Apps: Experimental & Innovation.

• Another nice-couple of articles at Quanta Magazine on quantum phenomena.

• In video/audio media:
• "Higher energy to find new particles?" from CERN. [3 minutes]
• A video on LUX at phys.org. [3 minutes]
• Acoustic levitation (with a high speed camera) on SmarterEveryday. [6 minutes]
• Monkeys and Coconuts problem on Numberphile. [13 minutes]

• Lastly, here is a gif of Pluto and Charon from New Horizons:
  
  
  

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:
  

  Expecting to #RestartLHC last week of March, says Director of Accelerators at Press Briefing @AAASmeetings. VNR #LHC https://t.co/FbVdwkqlB6
  — CERNpressoffice (@CERNpressoffice) February 15, 2015

• 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.

• The proton-electron mass ratio was the same 12 billion years ago as it is now.

• 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...

• Related, the Planckoscope got a sychrotron polarisation layer last weekend.

• 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?"

• There's more in the press on falsifiability, Carroll's call for its retirement, the Ellis and Silk comment, Tegmark's multiverse hierarchy, Dawid's post-empiricism etc. Frank Wilczek threw his hat into the ring: "I think falsifiability is not a perfect criterion, but it’s much less pernicious than what’s being served up by the ‘post-empirical’ faction. Falsifiability is too impatient, in some sense... It’s an important discipline, but if it is applied too rigorously and too early, it can be stifling."
  

  I get quoted, on falsifiability: http://t.co/oz2e7xRGgS Not often I refer to a "pernicious" "faction", but appropriate here.
  — Frank Wilczek (@FrankWilczek) February 12, 2015

• 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}".

• There is a new book out from Smolin, and also a biography on Bruno Pontecorvo. For reviews on the former see Woit or the guardian, for the latter there is a review by Freeman Dyson behind a paywall.

• 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. 

• If we're worried about that, maybe we should also worry about the star that passed through the cloud only 70,000 years ago according to research published last week.

• In video media...
• Ray Volkas public lecture, "The Known Unknowns of the Universe," at University of Tasmania. [1 hour]
• Sixty Symbols interviewed Clare Burrage (University of Nottingham) for a video on axions and the light shining through walls experiment [6 minutes]. There's also some bonus footage here [3 minutes].
• CERN released a video of some of the beam pipe upgrades performed during the long shutdown (with funky tunes) [3 minutes]. There's also a (less funky) partner article on the upgrades.
• ESA video on Rosetta's closest approach on 14 Feb. [4 minutes]
• An interview with Scott Aaronson (MIT professor, theoretical computer scientist, and blogger at Shtetl-Optimized) on QM, P=NP, ...
• Conversations with an Astrophysicist on Fast Radio Bursts with Scott Lewis, Katie Mack, and Emily Petroff. [44 minutes]
• How to construct a 17-gon at Numberphile, as first proven by Gauss. [13 minutes]

• There's a nice article at Washington Post on why science is hard to believe.

• Doing the rounds: Does science produce too many PhD graduates?

• There is an online petition circulating to adopt the term "climate denier" in lieu of the term "climate skeptic". The New York Times has a story. Meanwhile the Australian Academy of Science has released a 32 page booklet on climate change to dispel confusion and misinformation.

• 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?
  
  
  

• New Horizons is approaching Pluto and has imaged its moons Nix and Hydra (within diamonds):
  
  
  
• New closeup of Comet 67P/Churyumov-Gerasimenko from Rosetta's flyby:
  
  
  
  
  
• Hubble has imaged a galactic merger:
  
  
  
  
  
• Comet Lovejoy and its tail in the solar wind: