• John
  • Felde
  • University of Maryland
  • USA

Latest Posts

  • USA

  • James
  • Doherty
  • Open University
  • United Kingdom

Latest Posts

  • Andrea
  • Signori
  • Nikhef
  • Netherlands

Latest Posts

  • CERN
  • Geneva
  • Switzerland

Latest Posts

  • Aidan
  • Randle-Conde
  • Université Libre de Bruxelles
  • Belgium

Latest Posts

  • Vancouver, BC
  • Canada

Latest Posts

  • Laura
  • Gladstone
  • MIT
  • USA

Latest Posts

  • Steven
  • Goldfarb
  • University of Michigan

Latest Posts

  • Fermilab
  • Batavia, IL
  • USA

Latest Posts

  • Seth
  • Zenz
  • Imperial College London
  • UK

Latest Posts

  • Nhan
  • Tran
  • Fermilab
  • USA

Latest Posts

  • Alex
  • Millar
  • University of Melbourne
  • Australia

Latest Posts

  • Ken
  • Bloom
  • USA

Latest Posts

Warning: file_put_contents(/srv/bindings/215f6720ac674a2d94a96e55caf4a892/code/wp-content/uploads/cache.dat): failed to open stream: No such file or directory in /home/customer/www/quantumdiaries.org/releases/3/web/wp-content/plugins/quantum_diaries_user_pics_header/quantum_diaries_user_pics_header.php on line 170

Archive for May, 2014

The summer conference season starts Monday and QD will be there at every turn.

Hi Folks,

On Monday, the University of Pittsburgh in the US has honor of kicking off the 2014 summer conference season with the Phenomenology 2014 Symposium, and on its tail will be the Americas Workshop on Linear Collider at Fermilab also in the US, and beyond that are more results from around the world. Notably, the International Conference on High Energy Physics (ICHEP 2014) will be held in Valencia, Spain, and Supersymmetry 2014: The International Conference on Supersymmetry and Unification of Fundamental Interactions will be at the University of Manchester in England. Both ICHEP and SUSY are biannual conferences, and the last time ICHEP was held the Higgs discovery was announced. Whatever great result is announced this summer, QD will be there…. and possibly even giving the talk. 🙂 So check out the list below and start planning your summer getaway. (Note: For a great list of conferences/schools/and workshops that is regularly maintained, see Heather Logan ‘s (Carleton) conference page).

Happy Colliding

– richard (@BraveLittleMuon)

Phenomenology 2014 Symposium (#Pheno14)

Dates: 5-7 May. Host: University of Pittsburgh. Homepage


Americas Workshop on Linear Colliders 2014 (#AWLC14)

Dates: 12-16 May. Host: Fermilab.  Homepage

International Conference From the Planck Scale to the Electroweak Scale (#Planck14)

Dates: 26-30 May. Host: Institut des Cordeliers. Homepage

Muon Accelerator Program 2014 Spring Workshop (#Muon14)

Dates: 27-31 May. Host: Fermilab. Homepage

Large Hadron Collider Physics (LHCP) Conference (#LHCP14)

Dates:  2-7 June. Host: Brookhaven National Laboratory and Columbia University. Location: Columbia University. Homepage.

International Conference on Neutrino Physics and Astrophysics (#Neutrino14)

Dates:  2-7 June. Host: Boston University, Harvard University, Massachusetts Institute of Technology, and Tufts University. Location: Boston University. Homepage

LoopFest XIII (#Loop13)

Dates: 18-20 June. Host: New York City College of Technology. Homepage


7th Future Circular Collider / Tri- Large Electron Positron Physics Workshop (#TLEP)

Dates: 19-21 June. Host: CERN. Homepage

International Conference on High Energy Physics 2014 (#ICHEP14)

Dates: 2-9 July. Location: Valencia, Spain. Homepage

Coordinated Theoretical-Experimental Project on QCD Summer School (#CTEQ)

Dates: 8 – 18 July. Host: Peking University (PKU), Beijing. Homepage

Pre-SUSY 14 Summer School (#SUSY14)

Dates: 15-19 July. Host: University of Manchester. Homepage

Supersymmetry 2014 (#SUSY14)

Dates: 21-26 July. Host: University of Manchester. Homepage

SLAC Summer Institute (#SSI14)

Dates: 4-15 August. Host: SLAC. Homepage


A fish out of water

Thursday, May 1st, 2014
Note:  The following is a contribution from Lindsay Kroes, a talented and insightful University of Waterloo undergraduate student who spent a four-month work term at TRIUMF in the communications office. Upon being asked what she would tell her peers about the lab when she returned to campus this summer, Lindsay took to pen and paper to describe her experience.

“Fish out of water” doesn’t even begin to describe how I felt on my first day at TRIUMF.

The initial welcome meeting and the Health and Safety seminar were part of the usual on-boarding routine, but as soon as I set foot on the TRIUMF site, this co-op job began to feel a whole lot different than any of my past experiences.

Along with the flock of other new co-op students, I followed our guide along labyrinthine tour route, along catwalks which overlooked vast halls of humming equipment, up steep staircases flanked by tangles of tubes and cords, and through enormous halls dominated by cranes and concrete blocks. Everything I saw was foreign to me – and the explanations coming out of our guide’s mouth did little to dispel my confusion.

Of course I had googled “what is a cyclotron” before my interview. I had even signed up for an open-online Intro to Physics course (although in the bustle of the Christmas holidays, I only got through the first module). This was paltry preparation for what awaited me at TRIUMF, where physicists work at the very cutting edge of their field. See, in my studies, there’s more talk about soliloquies than supersymmetry… more focus on alliteration than acceleration. Bridging the gap between English literature and subatomic physics was going to take a lot more googling than I had initially accounted for.

The first few days I felt like I was drowning in a deluge of new and incomprehensible information.

“The LHC accelerates particles to 99.9999991% the speed of light!”

“TRIUMF’s cyclotron tank must support 2,600 tons of atmospheric pressure.”

“Beamline temperature is kept at negative 258 degrees Celsius; cryogenic pumps literally freeze the air out of the beamline.”

These were scales and concepts that I was completely unaccustomed to considering. It was difficult to wrap my head around the fact that within the convoluted maze of metal cylinders and cables of the DRAGON experiment, star explosions from the early universe were being re-created and studied. Or the fact that the blinking, droning computers that I glimpsed through the window of the ATLAS Tier-1 Data Centre held data that had travelled through a single wire all the way from Switzerland – data which may transform our understanding of the basic building blocks of the universe.

My first article assignment – a historical interest story about cyclotron development – found me poring through the pages of a scientific paper, decoding it line-by-line with the help of my co-workers and the “simple English” option of Wikipedia. In some sentences, it was difficult to discern which words were the verbs and which were the nouns. During interviews with scientists, I couldn’t even find the correct vocabulary to ask the question (let alone grasp the answer), and my article drafts were frequently returned rife with revisions, correcting the grossly inflated claims or blatant inaccuracies I had inadvertently reported.

When I explained to others – both within the lab and outside – where I was working, I was often met with raised eyebrows. “How did you end up there?” they asked, and I began to wonder myself. How could someone with no science background whatsoever find a place for themselves in one of Canada’s premier science laboratories?

I found the answer myself during one of my favourite writing assignments of the term, in which I accompanied a TRIUMF scientist to a Human Library event at a local high school, which connected grade nine students and science professionals for brief question-and-answer sessions. At one point during the discussion, he said, “Science is a human endeavor.”

This was a new idea to me. It had seemed that science was about calculations, machinery, technology, statistics – very far indeed from the “humanities” fields where I felt at home. However, the “human side” of science was apparent in the respect he expressed for colleagues and the obvious passion which fuelled his long career in academic research.

It was impressed upon me later in the term in the many tributes to Erich Vogt, an internationally-esteemed scientist and one of TRIUMF’s founding directors, who passed away during my term at TRIUMF. Erich was well-remembered for the incredible legacy he left to the physics community– but also for his prized tomato plants, his jovial sense of humour, and his strong ability to forge meaningful connections with people of any nationality and background.

The human side of science is also visible every day in the camaraderie that exists at TRIUMF – the feeling that “we’re all in this together,” especially at crunch time, when deadlines for high-priority projects are looming or important VIP visitors are knocking at the door.

It was demonstrated to me many times in the enthusiasm that scientists have for their work, as well as their patience and willingness to explain it – even to someone who couldn’t tell the difference between a neutrino and a quark if her life depended on it.

I realized that behind the baffling facts and figures, the state-of-the-art technology, and the data points flashing by on Powerpoint slides, there are people who are driven by the desire to give something of value to this world.

After four months of trying, I still may not understand precisely what they’re doing – but that doesn’t mean I can’t be inspired by it.

– Lindsay Kroes, TRIUMF Communications Assistant



Since IceCube was proposed, people have been claiming that you can get a new view of astrophysics by using particles instead of light, and we were pretty sure what the journey would look like. It hasn’t gone quite in the order we expected, but we’re getting that new view of astrophysics, and also, a few years later, filling in the steps we expected to fill first. When we find bits of scientific evidence in a different order than we expected, does that change how excited we get about them?

Sunrise over the IceCube laboritory

The sunrise at the South Pole over the IceCube laboratory, the central building on top of the IceCube Neutrino Observatory.

We been expanding astronomy since it started. First, astronomers used telescopes to resolve visible light better. Later, they expanded to different regions of the light spectrum like x-rays and gamma rays.  Then, it was a small step to expand from gamma rays, which are easier to think of as particles than as waves, to particles like the atomic nuclei that make up cosmic rays. Neutrinos are another kind of particle we can use for astronomy, and they have unique advantages and challenges.

The hard part about using neutrinos as a messenger between the stars and us is that neutrinos very rarely interact with matter. This means that if thousands pass through our detector, we might only see a few. There are some ways around this, and the biggest trick IceCube uses is to look in a very large volume. If we look for more neutrinos at a time, we have more of a chance of seeing the few that interact. The other trick is that we concentrate on high energies, where the neutrinos have a higher chance of interacting in our detector.

The great thing about using neutrinos as a messenger is that they hardly ever interact, so almost nothing can stop them from arriving at our door. If we see a neutrino in IceCube, it came to us directly from something interesting. We know that its direction wasn’t deflected in any magnetic fields, and it wasn’t dimmed by dust clouds or even asteroid clouds. Every (rare) time we see a high-energy neutrino, it tells us something about the stars, explosions, or black holes that created it.

That’s the story that people like Francis Halzen used to get funding for IceCube originally, and around Madison we still get to hear him tell this story, with his inimitable accent, when he speaks at museums or banquets.

Comparing neutrino astronomy to other new 20th century advances in astronomy, we expected the development of the field to follow a certain story.

We expected that first we would see a “diffuse” signal. This would be part of a large sample including a lot of background events, but some component would only be explained by including astrophysical sources. In IceCube, one of the best ways of reducing background noise is to look for events traveling up through the Earth, since only neutrinos can pass through the Earth. We could also look at high energies, since backgrounds like atmospheric neutrinos fall off exponentially with energy. So we thought the first diffuse astrophysics signal would come from the high-energy tail of an upgoing sample.

After that, we expected to resolve the diffuse sample into some clusters, and after a few of the clusters remained consistent, to declare them astrophysical sources.

What we did instead was to skip to the end of this story. We found astrophysical neutrinos first, and then a diffuse upgoing signal only two years after that (just this past spring). The exciting part about finding this recent diffuse signal isn’t that it’s the first detection of astrophysics, or even the strongest. It’s exciting because it follows the story we thought neutrino astronomy was going to follow.

The first detection was exciting too. That used a different kind of analysis: we identified only a few events (28 in two years) that were extremely likely to be from astrophysical sources. These were so special that each one got a name, using the theme of the Muppets, from Sesame Street and the Muppet Show. One is named Bert, one Ernie, one Mr. Snuffleupagus, one Oscar the Grouch. If we keep analyzing our data this way and eventually get enough events, we can expand to the Muppet Babies cartoons and various muppet movies, even including things like Labyrinth that used Jim Henson’s talents but not the muppets specifically. I’m personally a big fan of the muppet naming scheme, partly because it draws from a cannon recent enough that it includes several women and many kinds of diversity. When naming events is our biggest problem, it will be a great day for neutrino astrophysics. For formal publications, we usually say “HESE” for “High Energy Stating Event,” instead of “muppets.”

The two bedrock assumptions of the muppet analysis were that (1) we’re the most interested in the highest energy events, and (2) the events must have started within the detector; they must be “contained.” That containment requirement means that they must have been neutrinos and not cosmic rays, since comic ray showers contain lots of stuff besides neutrinos that arrives at the same time. We can assume at the highest energies that no cosmic ray could make it through the outer layers of our detector without leaving a trace (unpacked: cosmic rays must leave a trace) but at lower energies some cosmic ray muons can steak through. For the first muppet analysis, we get around this by just looking at the highest energies.

This is backwards from what we expected in two ways: first, the sample we get is mostly from neutrinos coming from above the detector, and second, there are almost no background events in our sample, so we don’t have to include directional clustering to know that we’ve seen astrophysics.

The sample is mostly downgoing because the highest energy neutrinos are blocked by the Earth. Higher energy neutrinos are more likely to interact than low-energy neutrinos; it’s the opposite of our momentum-based intuition from faster cars slamming through walls without stopping. It’s a popular trivium that neutrinos can pass through lightyears of lead without interacting, but that’s only true at low energy scales like the neutrinos from nuclear reactors. At IceCube astrophysics scales, it takes only our tiny planet to stop a neutrino. So the muppet events we do see are mostly ones that don’t pass through the Earth.

Since the muppets sample has almost no background events (at the very most, 10 of the 28, but we don’t know which 10), we don’t need to do a clustering analysis. Traditionally, we thought this was the most promising way to find neutrino point sources, and the background would be neutrinos from interactions in the Earth’s atmosphere. But at PeV energies, there aren’t enough atmospheric neutrinos to explain what we saw, so each event in the new analysis is potentially as interesting as a cluster would be in the old analysis.

We haven’t yet seen clusters using the old techniques, and when we do, it will probably be celebrated by a small party, an email around our collaboration, some nights out for the people involved, and a PhD for someone (or a few someones). But it won’t be the same cover-of-Science-Magazine celebration (that was Mr. Snuffalupagus on the cover) and press coverage that we had for the first discovery. It will be a quiet victory, as it was for the recent diffuse result.

While it doesn’t have to follow the script we expect it to, science can still sometimes choose to follow a familiar plotline. And we are comforted by the familiarity.