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Michael DuVernois | Wisconsin IceCube Particle Astrophysics Center | USA

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Thinking about Cosmos, Mark II

Tuesday, April 8th, 2014

I’ve just been watching the first couple of episodes of the new, reborn, perhaps rebooted, Cosmos. About 4 million people have been watching each of the episodes when broadcast. Out of a US population of about 300 million. Said that way, it doesn’t sound like a huge success, but science has much less of a grip on the American public than science fiction (or at least folks in spandex hitting each other over the head) or comedy about scientists. Over the years, it’s said that Sagan’s Cosmos has been the most watched PBS series world-wide, ever, and I have confidence that the new one, with current special effects, and its hooks to the 2010s rather than the late 1970s, will be watched for many years to come.

Different times and different shows. It’s worth thinking about why this isn’t a PBS show today. Why is that? And why are there still creationists around to poke holes in our schools?

Anyway, what I’ve seen so far, I’ve liked quite a bit. There are plenty of eloquent positive reviews out there, so let me highlight one thing of which I am not a fan. With the excellent special effects, along with the excellent astronomical images available, it’s not always clear in the show what is a real image and what is artwork. In Sagan’s Cosmos, we see visualizations and we see telescopic views, and we can know which is which. With the current Cosmos, it’s a lot harder to tell. And a third category, simulations also poke in somewhere between the models and true imaging. Simulations based on the physics, so therefore “true” and “correct,” but not real images of objects in the sky. I’ve seen NASA artist renditions clearly marked in the corner. It would be a nice addition to the show, not to justify the scientific validity but to clarify, to mark the boundaries of what we see, what we know, and what we conjecture. Three different parts of the science.

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IceCube Guest blog: TeVPA Conference

Thursday, September 26th, 2013

I asked if my IceCube and ARA colleague Mike Richman (University of Maryland) could write up something for the meeting he was attending. Thanks much, Mike!

During the last week of August, the annual TeV Particle Astrophysics, or
TeVPA, conference was held in Irvine, CA. IceCube and neutrino astrophysics
were very well represented at the conference. The opening talk of the
conference was “Results from IceCube”, presented by Albrecht Karle [1].
After introducing our detector and its objectives, the PeV events and the 26
other High Energy Starting Events (HESE) were highlighted in some detail.

The HESE are a set of very bright events in which neutrinos interacted in
the ice within the instrumented volume of IceCube itself. So far, IceCube is
cautiously reporting this result as “evidence” for high-energy
extraterrestrial neutrinos. We need to analyze more data to reach the
standard “discovery” threshold of about a 1 out of 2 million chance that our
data is the result of an especially sneaky terrestrial background.
Nevertheless, the HESE are generating a lot of excitement in the community.
Later on Monday, the events were described in more detail by Claudio Kopper
[2], while Joanna Kiryluk [3] helped put them in context with a discussion
of other IceCube searches for cascade-like events. Ranjan Laha [4], a
non-IceCube theorist, presented an outsider’s perspective on common
questions about the HESE.

Also on Monday, Jake Feintzeig [5] presented results from IceCube searches
for neutrino point-sources, and I [6] presented results from searches for
neutrinos correlated with gamma-ray bursts. Ignacio Taboada [7] presented a
search for a correlation between gamma-ray bursts and the 28 HESE. No
neutrino signal was found in any of these searches; however, many models
suggest that if these neutrino sources exist, we will need to take data for
longer before we can see them.

On Tuesday, Shigeru Yoshida [8] and Aya Ishihara [9] discussed scenarios in
which the extremely high energy neutrino flux levels at IceCube can
constrain cosmological models. Serap Tilav [10] gave a provocative talk in
which she explored a fit for the cosmic ray composition using the spectrum
across all energies as measured by many experiments. On Thursday, Markus
Ahlers [11] discussed multi-messenger — gamma, neutrino and charged
particle — tests which could be used to identify the sources of the HESE.

During the conference, there were talks by IceCube and non-IceCube
researchers alike in which it was said that, in light of the HESE, we have
entered the era of neutrino astrophysics. And while IceCube is currently
leading the field, we are certainly not alone. TeVPA also featured talks on
ANTARES and KM3NeT [12], neutrino experiments in the Mediterranean sea, as
well as ANITA, EVA and ARA [13] and ARIANNA [14], which search for radio
emission from the highest energy neutrinos interacting in the South Pole
ice. There was even a talk [15] on the possibility of using ultra high
energy neutrinos to constrain the depth of outer ice layers on moons like
Europa. It’s an exciting time to be working in neutrino astrophysics!

All material presented at TeVPA 2013 is available here: TeVPA2013.

Individual talk URLs:

[1] https://indico.cern.ch/contributionDisplay.py?contribId=0&confId=221841
[2] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=104&confId=221841
[3] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=113&confId=221841
[4] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=103&confId=221841
[5] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=99&confId=221841
[6] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=101&confId=221841
[7] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=102&confId=221841
[8] https://indico.cern.ch/contributionDisplay.py?sessionId=2&contribId=10&confId=221841
[9] https://indico.cern.ch/contributionDisplay.py?sessionId=10&contribId=34&confId=221841
[10] https://indico.cern.ch/contributionDisplay.py?sessionId=4&contribId=56&confId=221841
[11] https://indico.cern.ch/contributionDisplay.py?sessionId=6&contribId=96&confId=221841
[12] https://indico.cern.ch/contributionDisplay.py?sessionId=2&contribId=1&confId=221841
[13] https://indico.cern.ch/contributionDisplay.py?sessionId=2&contribId=11&confId=221841
[14] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=106&confId=221841
[15] https://indico.cern.ch/contributionDisplay.py?sessionId=9&contribId=108&confId=221841
[16] http://indico.cern.ch/conferenceDisplay.py?confId=221841

 

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IceCube High Energy Events

Wednesday, July 17th, 2013

prl

The IceCube TeV events are now in print in Physical Review Letters. With a nice cover image… The paper is available on arxiv. There has been a lot of speculation among theorists, and there are many more neutrino events in newer analyses which have been shown in meetings. So, just a quick update here…

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IceCube probable astrophysical events

Monday, May 20th, 2013

Okay, so there hasn’t been an official IceCube press release on this, not until the paper finishes collaboration review and is posted on the Arxiv, but there have been some talks showing neutrino events observed by IceCube which are almost certainly astrophysical in origin. Short version, neutrino astronomy is now a real thing. We are observing the universe in photons (ever since we looked up at the night sky, and starting with Galileo with increasingly sophisticated instruments) and also in neutrinos (which travel undisturbed from deep within the astrophysical objects, reflecting the nuclear interactions deep within).

One of the over 5000 DOMs (Digital Optical Modules) which make up the IceCube Observatory being deployed into the ice.

There’s a nice Gizmodo article with interesting comments.

University of Wisconsin news item.

Phys.org coverage of the news item.

The BBC news article.

Nature blog entry.

New Scientist entry written by our friend Anil who got to visit IceCube during construction.

Since the middle of last week, the news are spread around and there are Russian, Spanish, and French language versions (at a minimum!) of the news. Previously, only the neutrinos from Supernova 1987A had been seen from beyond the sun and the Earth’s atmosphere. Analysis is still ongoing, so this isn’t a final result by any means, but it is a proof-of-functionality of the IceCube detector and of neutrino astronomy.

Addition:

Scientific American’s article includes good quotes from the three Wisconsin-Madison postdocs who led the analysis, Nathan, Claudio, and Naoko.

 

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IceCube (and other) Winter-Overs at the South Pole

Monday, October 22nd, 2012

One of the questions that gets asked to most often is about the folks who run the IceCube experiment over the winter. Who are these folks? What does it take to spend fourteen months at the South Pole? Six of those months in darkness with the sun set below the horizon. So I’ll try to answer some of these questions, mostly by linking to what the winterovers themselves say. (And to their amazing aurora photos.)

Each year, the IceCube project advertises for the two IceCube winterover positions:

Winter Over Positions
Winter-overs deploy to Antarctica continuously for 14 months, mid-October to mid-November. Individuals participate in a wide range of activities and must pass physical and psychological evaluations of their ability to live and work in remote and high altitude locations. Degree requirements: M.S. in Electrical Engineering, Computer Science, Physics, or a related field; B.S. with substantial related field experience (equivalent to a Master’s Degree) will be considered.

Sometimes the person is already a collaborator, or affiliated with IceCube, perhaps a recently-completed graduate student, but most often the person is from a different science field. The winterover is responsible for keeping the detector running through the winter with some help/supervision from the Northern Hemisphere, but mostly independently. The laboratory is about two kilometers away from the South Pole Elevated Station, so it’s a good cold walk out to the experiment…

But the views are astonishing!

And you can see some of Sven’s aurora shots here. Sven and Carlos are this past year’s winterovers for IceCube, their reports can be seen at the IceCube website news listings. There’s a good “What is a Winterover” there as well.

At Pole there are two seasons, Summer and Winter. In the Summer, there is sunshine and a population of at least a 150 people at the station. The weather is relatively warm, from -40C (= -40F) up to an all-time record high temperature of +10F last Christmas. This is when the work is done building new experiments, when most of the scientists and engineers who work down there visit for a few weeks, or six weeks, or eight weeks. During IceCube construction, the drill teams would core down a mile in the ice for each of IceCube’s 86 strings during the Summer. The Winter is defined by the departure of the last aircrafts (jet fuel starts to gel as it gets too cold), the setting of the sun, and truly cold (-70C, -100F) temperatures. In the Winter, the South Pole Station is down to about fifty hardy souls.

I recently found this interesting Winterover Statistics page that gives some insight into the folks who have wintered for a record number of South Pole winters (five in a row! nine total times!). Not for me! Though had I known about it, perhaps back when I was twenty and single…

 

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PACIFIC 2012 and the Dark Taxa

Friday, October 19th, 2012

Well, this is a bit of a late posting for me, but it’s been a crazy few months with a house sale, house purchase, daughters starting high school, and a frantic build of two stations for the ARA (Askaryan Radio Array) experiment that we’ll deploy at the South Pole this Austral Summer. More on most of those topics soon, but a little report on the PACIFIC 2012 conference and some biology that I learned while I was there. (Any and all biology in this article is as reported by myself, an astroparticle physicist, so apologies to actual biologists, this is posted out of “hey, that’s neat” intellectual curiosity and not some sort of physicist supremacy theory.)

So, the PACIFIC 2012 conference was held in early September in beautiful Moorea in French Polynesia. I felt pretty guilty heading to a meeting in paradise, so I did my best to bring back some gifts… It’s an annual, small meeting on particle astrophysics and cosmology, held at the Richard B. Gump South Pacific Research Station run by the University of California-Berkeley. The meeting was especially interesting to me with the small group of scientists there, in a relatively isolated environment, and with a good mix of experimentalists and theorists. I gave a talk on the IceCube experiment (talk is post here, NB: large file and somewhat technical), including some recent results on the gamma-ray bursts and also a few of the first bright (PeV) events seen by the telescope.

I did manage to find some time to go snorkeling during the meeting. There were a lot of fish and sea creatures in the protected reef waters of the lagoon, and in fact Moorea featured in a recent National Geographic magazine article exploring the living content of a cubic foot of the coral reef. It’s a ridiculous variety and density of life, teeming life in great numbers of species and individuals, in every corner, every niche of the Earth. But, if you read why Moorea was chosen as one of the locations (in work performed at the Gump Center) you find it’s because the isolated French Polynesian islands (it’s a really long flight, and look at it on Google Earth, far from the US, Australia, New Zealand, Asia, and Hawaii) have the least biodiversity on Earth.

Basically, it’s a really long way from everything else, and relatively few species (comparatively!) got there, established themselves, and evolved in place. So, in a manner that a physicist would approve of, Moorea can be used as a simple model of an ecosystem for systematic study. It’s far simpler than most other ecosystems, and many of the species present have their time and method of introduction to the island known. Some arrived with the Polynesian voyageurs, others with colonial masters, and others as accidental tourists in the jet age.

Okay, so you have simple system that you’re going to use as a template for more complex systems later, and maybe one of the first things that you want to do is catalog the species present on the island, in the soil, and in the lagoon. The Biocode project at Gump tries to do just this. Identify all of the species. Since I last took a biology class of course this is not just a process of identifying the species by its characteristics (Wikipedia background on taxonomy) but also via the DNA characterization of the species. (I must put a call out here to the brilliant DNA analysis work on restaurant sushi. Check it out if you haven’t before.) In fact, increasingly the species being discovered aren’t being formally named, or even identified in the sense of “here’s a canary, you can tell by its song, and this brilliant plumage” but rather by the existence of a unique DNA sequence.

For example, you can identify all of the critters you can (in Moorea, down to about a couple of mm in length), record their DNA, and then take the contents of a fish stomach and sequence that DNA. In the stomach you find the DNA of species that you had not previously identified. In fact, it seems that many, or most, species do not have a catalog entry, a sample pinned onto a board in the basement of the natural history museum, they just have some DNA in the instrumentation in the laboratory. These are the dark taxa, genetic information without the classical context of the detailed, properly named, taxonomy entry. The name is nicely analogous to the Dark Matter. Most of the mass of the universe is not in ordinary, observed matter, but in a “dark matter” which interacts gravitationally but is otherwise not observed directly (yet).

The Dark Taxa was introduced by Roderic Page who was considering the entries in species catalogs and noting the explosion in the number of species identified only genetically, with no classical taxonomy. Estimates seem to vary, but perhaps 90% of the animals (let’s not even think about the bacteria) are unknown. The already plenty-amazing world is that much richer still. Most species are unknown, and in fact the definition of species and broader classifications are moving rapidly with the ability of genetic tools to make a more reasonable “a is closely related to b” based on evolutionary distance rather than appearance. The Biocode effort on Moorea was making use of large scale databases, sequencing everything biological that the researchers could find on the island, and working through the classifications via software. It’s a very different biology than I recall from class, more analytic and less descriptive. I hesitate to mention the perhaps somewhat similar division between classic descriptive astronomy (“twelve barred spiral galaxies”) and astrophysics (“we modeled the bar formation with a 3-D hydrodynamics code”) but it does have some of that feel.

Okay, so I went to a tropical paradise, talked physics, and got pretty excited about biology, in particular biological classification. It was a good trip.

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Oscillation results from DeepCore (IceCube sub-detector)

Monday, June 11th, 2012

See the press release here.

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IceCube talks at Neutrino 2012

Tuesday, June 5th, 2012

Alas, I am not at the meeting. We had a HAWC collaboration meeting in Santa Fe last week and the next couple of weeks I need to be working on ARA hardware for South Pole delivery this season. The official IceCube Collaboration announcement for the Neutrino conference follows:

The IceCube Collaboration is pleased to announce participation in the upcoming 25th International Conference on Neutrino Physics and Astrophysics June 3-9, 2012 in Kyoto, Japan. The conference, known as “Neutrino 2012,” is a premiere international meeting covering neutrino physics, current and future detection technology, and neutrino beams.

IceCube principal investigator Francis Halzen will chair the Experimental Neutrino Astronomy session on Friday, June 8th. The following IceCube collaboration members will give talks during the session:

IceCube spokesperson Greg Sullivan, University of Maryland, will cover “IceCube: Diffuse neutrinos from GRB/AGN”; Aya Ishihara, Chiba University, “IceCube: Ultra high energy neutrinos”; Albrecht Karle, University of Wisconsin-Madison, “A review of future experiments”; and Markus Ahlers, University of Wisconsin-Madison, “Neutrinos as a probe of ultra-high energy cosmic rays.”

Carsten Rott from the Center for Cosmology and Astroparticle Physics at Ohio State University will present “A review of indirect WIMP search experiments” during the dark matter session on Saturday, June 9.

IceCube Collaboration members will also be in attendance to present posters, including topics such as the search for dark matter, neutrino oscillations, high energy neutrino point sources, neutrino radiography, supernova detection, and possible IceCube extension.

A comprehensive list of poster presentations includes:

Poster session 1, Monday, June 4th

  • “Neutrino radiography with IceCube Neutrino Observatory” by Kotoyo Hoshina and Hiroyuki Tanaka
  • “Searches for neutrinos from GRBs with IceCube” by Erik Blaufuss
  • “Supernova detection with IceCube and beyond” by Ronald Bruijn
  • “Atmospheric neutrino oscillations with IceCube/DeepCore” by Andreas Gross
  • “Search for secluded dark matter with the IceCube Neutrino Telescope” by Jonathon Miller

Poster session 2, Tuesday, June 5th

  • “Search for neutrinos from the galactic plane and other astrophysical extended sources with IceCube” by Naoko Kurashashi Neilson
  • “Extending IceCube DeepCore with PINGU” by Darren Grant and Elisa Resconi
  • “Towards an extragalactic supernova neutrino detector at the South Pole” by Markus Voge, Nora-Lynn Strotjohann, Sebastian Boeser, and Marek Kowalski
  • “Search for dark matter captured in the sun with the IceCube Neutrino Observatory” by Matthias Danninger, Carston Rott, and Erik Strahler

Poster session 3, Friday, June 8th

  • “A search for the extremely high energy cosmogenic neutrinos with the IceCube 2010-2011 data” by Keiichi Mase
  • “Search for dark matter in galactic and extragalactic halos” by Carston Rott, Martin Bissok, and Jan Lünemann
  • “Search for high energy neutrino point sources with IceCube” by Sirin Odrowski

For more information about the conference, visit http://neu2012.kek.jp/index.html

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IceCube non-detection of neutrinos from GRBs

Thursday, April 19th, 2012

In a new paper in Nature, IceCube shows a solid, non-detection of neutrinos from gamma-ray bursts (GRBs). That is, the expected emission of neutrinos if GRBs were the sources of the highest energy cosmic rays was not observed. There had been a generally agreed model of GRB emission, and now it’s essentially ruled out. Cosmic rays remain a mystery…

More personal comments on this in a bit, but let me send along some of the news coverage in the shorter term:

IceCube popular version of the Mystery of the Cosmic Rays

IceCube press release

“Although we have not discovered where cosmic rays come from, we have taken a major step towards ruling out one of the leading predictions,” said IceCube principal investigator and University of Wisconsin-Madison physics professor Francis Halzen.

 

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More experimental details on the OPERA mistake

Tuesday, April 10th, 2012

I had been debating what word to use for the end of the title. Anomaly is clearly polite for just the sake of politeness. Debacle seems stronger than I’m willing to defend in a short posting, though would be happy to push such an interpretation in person. “Business” seems to be evasive. So mistake it is.

Matt Strassler now has significant details posted on a blog entry of precisely what happened.

This makes it clear that high-level issues such as the data analysis and the like were given a lot of thought, but that there was little or no low-level hardware examination of the experiment either before the announcement or in the wake of the excitement of the announcement. To me, as an experimentalist, this is very hard to understand. If I have an instrument which has made a shocking discovery (one that I and everyone else working on the project suspects is wrong, but have some slight hope that might be right) I’m going to want to tear the whole thing down and touch every piece, rebuild it, remake every connection, redo every calibration, and in the process possibly find (or just repair) the problem. This didn’t happen within the OPERA group.

The problem was eventually tracked to the now-infamous loose fiber optical connector and the data are understood to now make sense. Anyway, do read the account of the error and its discovery…

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