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Archive for February, 2015

Where Do I Come From?

Wednesday, February 4th, 2015

It’s the oldest question in the world and it occurs to every child, sooner or later: where do I come from? Mum and Dad of course, but where did they come from? Genetics only takes us so far; our line of ancestors actually stretches back beyond our first single celled forebears. Chemistry proceeds biology, and before that the world was made only of protons, neutrons and electrons. Now this takes us pretty far back, to the first second of the universe. In many ways, our fate was decided in this instant. The protons and neutrons we are made of formed a millionth of a second after the proverbial lights went on, condensing out of quarks. But where did the quarks come from?

Photo courtesy of NASA

Photo courtesy of NASA

Baryogenesis as a concept is not too difficult to follow. Every molecule you see around you is a survivor of a vast catastrophe that struck the early universe, when 30,000,000 of every 30,000,001 quarks in the universe were destroyed. The culprit of this disaster is antimatter – the bizarro version of matter. The crux of the matter is that matter and antimatter have a love-hate relationship; they annihilate each other, but also prefer to be created together. In the present day our universe is just too cold to create matter out of thin air (actually, through interactions with particles like photons), but this was not always so. When we go far enough back, at temperatures of about 10^13 degrees Celsius pair creation kicks off and the universe is filled with massive amounts of matter and antimatter. While this is lukewarm for a particle physicist there are more orders of magnitude between this temperature and the sun’s core than the sun’s core and you. From what I have said, the origin of matter doesn’t seem like much of a mystery; pair creation made matter. The problem is that it also made antimatter, and (according to the Standard Model) in equal amounts. When the universe cooled, matter could no longer be created, only destroyed, and so both matter and antimatter dwindled into nothing.

Creation (or destruction) of an electron-positron pair. Canny readers will notice that I have used this little diagram before.

Creation (or destruction) of an electron-positron pair. Canny readers will notice that I have used this little diagram before.

Clearly this is not the case – as any child can see, our universe is a populated and interesting one, filled with stars and planets and puppies. Above all, our universe is made of matter – no antimatter allowed. So there must have been a kind of discrimination against antimatter for some matter to survive this rampant destruction. Either this asymmetry between matter and antimatter existed from the start, as some sort of initial condition, or it somehow has dynamically evolved since then. Inflation dilutes any primordial asymmetry even more than a homeopathic remedy, so there must have been some matter creating process – baryogenesis. In any case, simply citing “initial conditions” is almost like saying “just because”, which never really seems to work with children.

When you need to explain something, it is usually best to start by what broad features your theory must have. For baryogenesis, Sahkarov did this back in 1967. For any theory (that doesn’t violate CPT) to create an asymmetry between matter and antimatter, three conditions must be satisfied:

  1. Baryon number must be violated. If you wish to count the number of protons and neutrons, it turns out that assigning them a quantity called “baryon number” is useful, a proton and neutron each have a baryon number of 1, and a quark has a baryon number of 1/3. Antimatter versions have a negative baryon number. The process that leads to the predominance of matter over antimatter, and so baryons over anti-baryons, is referred to as “baryogenesis”. It turns out that the total baryon number of the universe is conserved under perturbative effects in the Standard Model, what is known as an “accidental symmetry”. If we want more protons than antiprotons this number cannot be inviolate. There is a similar counting of electrons and neutrinos called lepton number, which is also believed to be broken. Unfortunately as neutrinos are extremely difficult to observe there is no direct evidence of a total lepton asymmetry.
  2. Matter and antimatter must be treated differently. This means that charge conjugation (where you swap particles with antiparticles) and charge-parity conjugation (swap particles with antiparticles and also reflect them like a mirror image) cannot leave the physics unchanged. More succinctly, C and CP must be broken. While C violation is trivial (the weak force violates C maximally), CP is almost entirely preserved in the Standard Model. This is both a major failing of the Standard Model and a fantastic prediction – we know that CP violation is absolutely fundamental to our universe, and that there must be more of it than we have seen so far. You have probably seen CP violation mentioned many times, both on this site and through news reports. The necessity for CP violation to explain our own existence is the real reason why CP violation deserves our attention.
  3. The universe must go out of thermal equilibrium. In thermal equilibrium any process creating a baryon asymmetry would be balanced by its reverse. Fortunately for us, the fact that the universe expands creates periods of thermal non-equilibrium, such as phase changes (like when the Higgs mechanism breaks the electroweak symmetry of the Standard Model).


While the Standard Model does technically satisfy all three of these, it does so in a trivial way. The amount of CP violation is far too low, and a universe in which the Standard Model is entirely correct never gets far enough out of equilibrium to allow a large difference in matter and antimatter to form even if it did violate CP more. The only really useful element that the Standard Model has is baryon number violation; a non-perturbative process called sphalerons occurs above the electroweak phase transitions which violates baryon and lepton number. More importantly, it preserves a linear combination of the two, so if you manage to make a baron asymmetry or a lepton asymmetry, you automatically get both. Theories like leptogenesis use this to turn a lepton asymmetry into a baryon asymmetry. While there are many possible scenarios that could have lead to the present day world (my own work is in one of these, asymmetric dark matter), the truth is that we simply don’t know which of these, if any, is correct.

Despite this being a question of the most fundamental kind, baryogenesis does not get nearly the same kind of media attention as dark matter or dark energy. Partly this is because we have little chance of experimentally finding an answer – baryogenesis could have occurred at almost any energy scale, which includes a good many far out of the reach of our colliders. But it is still important to push for an answer. Nothing is a better mark of our progress in understanding our origins than seeing how the question we ask about our origin evolves.


Every seven years or so a professor in a US/Canadian University can apply for a sabbatical leave. It’s a very nice thing: your University allows you to catch up on your research, learn new techniques, write a book, etc. That is to say, you become a postdoc again. And in many cases questions arise: should I stay at my University or go somewhere else? In many cases yearlong sabbaticals are not funded by the home University, i.e. you have to find additional sources of funding to keep your salary.

I am on a year-long sabbatical this academic year. So I had to find a way to fund my sabbatical (my University only pays 60% of my salary). I spent Fall 2014 semester at Fermilab and am spending Winter 2015 semester at the University of Michigan, Ann Arbor.

Here are some helpful resources for those who are looking to fund their sabbatical next year. As you could see from the list, they are slightly tilted towards theoretical physics. Yet, there are many resources that are useful for any profession. Of course your success depends on many factors: whether or not you would like to stay in the US or go abroad, competition, etc.

  • General resources:

Guggenheim Foundation
Deadline: September

Fulbright Scholar Program
Deadline: August

  • USA/Canada:

Simons Fellowship:
Deadline: September

IAS Princeton:
Deadline: November

Perimeter Institute:
Deadline: November

Radcliffe Institute at Harvard University:
Deadline: November

URA Visiting Scholar program
Intensity Frontier Fellowships
Deadline: twice a year

IAS Princeton (Member/Sabbatical):
Deadline: November 15

  • Europe:

Alexander von Humbuldt:
Friedrich Wilhelm Bessel Research Award
Humboldt Research Award

Marie Curie International Incoming Fellowships:
Deadline: varies

CERN Short Term visitors:
Deadline: varies

Hans Fischer Senior Fellowship (TUM-IAS, Munchen)
Deadline: varies
Some general  info could also be useful:

Many University also have separate funds for sabbatical visitors. So if there is a University one wants to visit, it’s best to ask.

Good luck!


What BICEP2 Got Right

Wednesday, February 4th, 2015
The region of the sky in which BICEP2 polarization, shown as dotted lines over Planck data. (Credit: ESA/Planck Collab. M.-A. Miville-Deschênes, CNRS, Univ. Paris-XI)

The region of the sky in which BICEP2 polarization was seen; the region is shown as dotted lines over Planck data. (Credit: ESA/Planck Collab. M.-A. Miville-Deschênes, CNRS, Univ. Paris-XI)

There has been a lot made of the fact that Planck and BICEP2 jointly released a paper last week saying that BICEP2’s original claim of a discovery of proof that the very early universe expanded mindbogglingly quickly – something that’s called inflation – was “wrong.”

[Note here I’m not going to go over any of the physics or terminology about the experiment in this post, there are other great sources for that. I compiled a list of them here back in March 2014.  This particular post is largely discussing the sociology of how one goes about releasing results like this, and then the discourse in the community that goes on afterward.]

A lot of the way the press has breathlessly reported this result has left me feeling a bit discombobulated because the version of the paper that BICEP2 actually submitted to a journal last year had already walked back strongly a lot of the claims of their initial announcement just two short months previous.  The team had clearly started seeing hints in others’ Milky Way Galaxy (MWG) radio loop data, and hearing from others who were expert with the possibilities that unusual dust properties might explain most of the “B-mode polarization” signal they had seen.  So they did the prudent thing and backed away from their initial claims in March 2014.  For the record, I want to quote verbatim the last few sentences of that paper (this is from the last version, the one from June 2014):

“We have pushed into a new regime of sensitivity, and the high-confidence detection of B-mode polarization at degree angular scales brings us to an exciting juncture. If the origin is in tensors, as favored by the evidence presented above, it heralds a new era of B-mode cosmology. However, if these B modes represent evidence of a high-dust foreground, it reveals the scale of the challenges that lie ahead.”

In other words, although they very much hoped and thought they were justified in their analysis from all everyone knew about MWG dust properties previously, they also were quite well aware already that the signal they had detected might be sourced mostly from anomalous dust, more than 7 months before today.

Before going further, I want to note for full disclosure that I say all this as someone who has a number of friends on the B2 (BICEP2) team, all the way from grad students and postdocs to more senior folk.  They are all upstanding and hardworking scientists.  And they have definitely endured some harsh criticism from various not-so-softly-spoken colleagues, publicly.  It’s not my place to say how the entire back and forth should’ve been conducted, except I would argue for civility as much as possible always in all spheres, even for very charged issues. (President Obama always pushes for as well, too, btw.)

Along these lines, I want to make very clear that I do not at all like the phrasing “B2 was totally wrong!!!” — because they did see B-modes in a region of the CMB power spectrum that people never had, and this was and is a major advance, and constitutes the largest part of their published paper.  Where they stretched was in not believing that those B-modes could be fully explained by anomalous dust, which is what the more recent results are pretty clearly demonstrating (but that doesn’t, and can’t, rule out primordial B-modes from inflation at a smaller level still, underneath).

So yes, it can’t have felt very good to be any member of the team after there were big celebrations and they seemed so sure. But the B2 observation was totally consistent with all physics we understand currently, and there was no fundamental reason they could not have been right.  Just turns out that interstellar dust apparently can exist with very different properties than we’re accustomed to.

At the same time — I will say: if you’re going to go out there and make claims like that, you do have to be prepared for the fallout.

Should they have not gone out and made a big splash?  Maybe.  But they were very sure of their signal, they spent over a year crosschecking it in every possible way they could think of — it’s just that they just reached too far for the interpretation, assuming too much about the dust being ‘normal.’  And once the evidence started piling up against that interpretation, they very rapidly started backtracking, and coordinating with others to crosscheck their interpretation of the data, vs. sticking to their guns.  That is indeed the way real science always works, and moves forward.

So yes — they overreached.  But they were not wrong in their observations, and that is the most critical part of observational and experimental science, indeed, I would submit.

That is how we most collaboratively and collegially get to the truth of the Universe.



The Black Hills of South Dakota may seem an unlikely location to hunt for dark matter, even if the name does seem fitting. If they are known for one thing, it’s gold – and gold requires a mine. Gold mining means deep underground caverns, which just happen to be the perfect home for low background experiments such as dark matter searches thanks to the cosmic ray shielding properties of thousands of feet of rock.

I am currently in Lead, S.D. working underground on LUX, the Large Underground Xenon detector. LUX sits in the Davis campus of SURF – the Sanford Underground Research Facility, an underground lab built in the Homestake gold mine. The Davis campus is named after Ray Davis, whose famous Homestake neutrino experiment was the first to detect neutrinos from the sun. LUX now sits in the same cavern that once housed his ground-breaking experiment.

To cut a long story short, LUX is a big tank of xenon that produces light when particles pass through it. We collect that light with sensors called photomultiplier tubes and search through the data for possible dark matter signals. In particular, we look for WIMPs – Weakly Interacting Massive Particles, the most promising dark matter candidate. Placing LUX deep underground in a mine cuts away lots of background from particles streaming down from space and the atmosphere, as those particles are absorbed by the rock. (For a bit of a more technical insight, I recommend this article, which was written during my shifts last year.)

But what do we, the physicists, actually do out here? Our detector is currently in WIMP search mode, waiting patiently for any sign of dark matter, but it needs a bit of a (human) hand. To give you an insight, here is a typical day in Lead, SD:

5.15am – I wake up. Getting up this early is a little unnecessary, but I like to have some time to wake up in the morning! I have a chat with my boyfriend back in London and spend some time reading my emails as I am 7 hours behind the UK over here.

7.00am – We leave to drive up to the mine. Lead is a tiny town and it only takes a few minutes. The streets look like they are straight out of a cowboy film!

Beautiful morning view from outside SURF. There are two shafts, we use the Yates. The Ross shaft is visible centre-right.

Beautiful morning view from outside SURF. There are two shafts, we use the Yates. The Ross shaft is visible centre-right.

7.15am – We arrive at SURF. We’re always a bit rushed; we grab our head torches and head to the changing area. Overalls, steel capped dirty boots, helmets, safety glasses, self-rescuers and the head torch all have to be donned. It’s unpleasantly hot, as the water running down the lift shaft must not be allowed to freeze. We take two golden tags with our name on and place one on a board to show we have gone underground, the other stays on your person (to identify your body…? Doesn’t bear thinking about!).

Me in my fashionable mining gear, 4850 feet underground at SURF

Me in my fashionable mining gear, 4850 feet underground at SURF

7.30am – The cage (literally a big metal cage that acts as our ride downwards) departs from ground level. The cage operators have impeccable timing and take care of opening and closing the door and contacting the hoist operator, who will lower us down from the surface. Usually the morning cage isn’t too busy (there is an earlier one at 7am) but it’s still not the most pleasant experience. Sometimes we are all a little too close for comfort – miners don’t tend to be small guys! Also, if you stand in the wrong place you get cold water dripping on you for the whole journey.

7.45am – The cage arrives at the 4850 level – 4850 feet underground. We leave the cage and head to the bootwash. LUX and the other main experiment at SURF, Majorana, both need clean conditions as they are low background experiments. Any dirt treaded in to the lab could contain radioactive elements that would be very bad for our detectors. For Majorana, the need for cleanliness is much higher than LUX, and so they have a cleanroom that requires them to wear special body suits, face masks and hair nets. I am extremely glad that isn’t necessary for LUX! After cleaning our boots, we remove all of our gear except for the glasses, change into clean steel-capped boots (I obviously have pink ones!) and new hard hats.

8.00am – Morning meeting. We all gather in the LUX control room and discuss the plan for the day. This can vary wildly depending on the decisions made in the weekly planning meeting. We may have taken data or seen conditions that suggest something needs investigating or fixing, or it might just be boring old WIMP search mode where nothing special needs to be done. The control room is the only place where we can remove our hard hats and safety glasses – stopping people leaving the room without them has to be done regularly!

12.00pm – We tend to take a break for lunch. Throughout the morning, everyone will have been going about their various shifting duties – monitoring all aspects of the detector, sampling xenon to check its purity, injecting krypton for calibration, refilling the liquid nitrogen store etc. We may have received some training from off-site system experts or attended a meeting, depending on what day it is. Conditions underground are pretty good, you start to forget where you are – only the lack of windows and bumpy walls remind you! During my previous visit 10 months ago we still had incinerator toilets – the less said about these, the better! They often broke down after the lunchtime rush and if you needed the toilet you had to put all your dirty mining gear back on and go to use the chemical toilets out in the mine. Now, thank god, we actually have running water!

View from the lower Davis. The water tank containing LUX is visible in the centre.

View from the lower Davis. The water tank containing LUX is visible in the centre.

4.00pm –If we are lucky, we get the cage up at 4. If something has gone wrong or there is enough to be done we may have to stay till the next cage at 4.45pm or even the latest at 5.30pm. In an emergency we may be able to come up later but we prefer to not have to do that! So it’s back to being squished in a damp dark cage full of South Dakotan miners!

6.00pm – dinnertime! Often someone will cook a group meal or we will head out to get food either in Lead, Deadwood or Spearfish. If it’s Friday, we go to Lewie’s for greasy burgers to do the “pub quiz” (I have been attempting to teach my American colleagues some proper English) . We tend to do very well in the trivia sections of the quiz, but the music round is our weakness. There’s too much country for us outsiders. The quiz host pulls several names out of a hat for prizes each week; so far on this trip I’ve won an extra large bud-light t-shirt (bear in mind I wear XS…) and some hot wings, which as a vegetarian I couldn’t eat!

8.00pm – depending on the person / how much work they have to do, some of us may continue to work. I mainly do analysis work and sometimes find I don’t have much time to get it done during the underground day so sometimes I try to get a bit done at night. I am also currently the shift manager so I have to fill in a shift report detailing what we have done each day.

10.00pm – bedtime. I’m wiped out by this stage and fall straight asleep, usually dreaming about LUX.

Devil's Tower

Devil’s Tower, Wyoming

But it’s not all hard work. Every other weekend we get 4 non-underground days, which gives us a little time to see the sights of South Dakota (or, if gambling is your thing, there are plenty of casinos in Deadwood)! On my last visit, I visited Mount Rushmore (smaller than you’d think) and Crazy Horse (much bigger than you’d think!), the latter being an enormous mountain carving that has been in progress for over 50 years – still, only his face is complete. If we go somewhere far, someone always has to stay close to SURF in case of an emergency – our detector might need us! This weekend we headed over to the neighbouring state of Wyoming to see Devil’s Tower; an ethereal protrusion of volcanic rock 1,267 feet above the surrounding ground! It was an incredible sight, although temperatures had dropped and I spent most of the time there jumping around trying to restore circulation to my hands. I have Raynaud’s syndrome, which means the moment I get slightly cold my fingers turn white and become extremely painful! We actually had -19 C (-2F) here in Lead a couple of days ago – not fun! Luckily, it’s warm underground!

Speaking of the weather, this time of year there’s snow, so much snow! It’s crazy to think how Britain comes to a standstill with schools and businesses closing when we get a tiny smearing of snow, whilst here several feet overnight is not uncommon. But life goes on in Lead, and we usually still make it up the hill to the mine!

The LUX collaboration. This is standard Lead weather!

The LUX collaboration, demonstrating a standard Lead winter! There seems to be a hairy impostor in this photo…

Lead is a place very different to London –  everyone is so friendly and pleasant! There’s no avoiding all human interaction like on the tube in London – everyone says hello! It is difficult eating as a vegetarian here, but most places have been accommodating and have allowed me to order special things (e.g. a salmon salad with no salmon, a Reuben with no beef!). The locals are always interested to hear how things are going at SURF. Amusingly, one resident excitedly asked “You’re from Pizza Lab?” after they heard us discussing the lab! One big shock to me, however, was finding out about the gun laws here in S.D. – concealed carry permits can be issued and apparently most people you see will be carrying a gun (maybe an exaggeration? But maybe not, you just can’t tell!). But then again all the gun laws in America seem alien to us Brits!

The staff at SURF are also extremely accommodating, helping us get underground in emergencies, and their health and safety policies are commendable. Right now, most shifters are getting trained as “guides” – each research team has a guide who is responsible for getting you to safety, whether that is above ground or in the refuge chamber.

The refuge chamber is something we all hope to never have to use. In the event that we cannot reach the ground from either of the two mine shafts, and that the rest of the mine is dangerous to inhabit (for example a fire causing a lack of oxygen), this is where we would go. It has carbon dioxide scrubbers, oxygen, water and a huge supply of “nutrition bars’ – rock hard bars containing a whopping 500 calories each so that someone could easily survive on two to four a day. There is enough oxygen for the entire underground population to survive for many days, awaiting rescue – but it’s not something we like to think about happening – especially since the toilets are just buckets!

As much as I prefer to be safely in front of my laptop, with no million dollar detectors in my hands and not facing the risks of working underground (note to self, do NOT go back on the Wikipedia list of mining accidents!), I do enjoy being on-site. It makes me feel like I’m actually part of something. We are the “underground crew”, a team of physicists travelling 4850 feet below Earth’s surface every day to take care of our precious detector. We keep things running smoothly, allowing LUX and our colleagues off-site to keep on searching for dark matter! Who knows, the Black Hills may yet bear some dark matter fruit!


ELBNF is born

Tuesday, February 3rd, 2015

This article appeared in Fermilab Today on Jan. 27, 2015.

The proposed experiment at the Long-Baseline Neutrino Facility would send neutrinos through the Earth's mantle from Batavia, Illinois, to Lead, South Dakota. Image: symmetry

The proposed experiment at the Long-Baseline Neutrino Facility would send neutrinos through the Earth’s mantle from Batavia, Illinois, to Lead, South Dakota. Image: symmetry

At approximately 6:15 p.m. CST on Jan. 22, 2015, the largest and most ambitious experimental collaboration for neutrino science was born.

It was inspired by a confluence of scientific mysteries and technological advances, engendered by the P5 report and the European Strategy update, and midwifed by firm tugs from Fermilab, CERN and Brookhaven Lab. Going by the placeholder name ELBNF (Experiment at the Long-Baseline Neutrino Facility), the newborn had the impressive heft of 145 institutions from 23 countries.

The new Institutional Board (IB), convened by interim chair Sergio Bertolucci, unanimously approved a Memorandum of Collaboration that launches the election of spokespeople and a process to develop bylaws. The IB also endorsed an international governance plan for oversight of ELBNF detector projects, in concert with the construction of the LBNF facility hosted by Fermilab.

The goal of this international collaboration is crystal clear: a 40-kiloton modular liquid-argon detector deep underground at the Sanford Underground Research Facility exposed to a megawatt-class neutrino beam from Fermilab with the first 10 kilotons in place by 2021. This goal will enable a comprehensive investigation of neutrino oscillations that can establish the presence of CP violation for leptons, unequivocally determine the neutrino mass ordering and strongly test our current neutrino paradigm. A high-resolution near detector on the Fermilab site will have its own rich physics program, and the underground far detector will open exciting windows on nucleon decay, atmospheric neutrinos and neutrino bursts from supernova detonations.

Unlike most births, this one took place at an international meeting hosted by Fermilab; there was room for nearly all the friends and family of accelerator-based neutrino experiments. One of the critical items flagged at this meeting is to find a better name for the new collaboration. Here are a few of my unsolicited attempts:

nuLAND = neutrino Liquid ArgoN Detector

GOLDEN = Giant OsciLlation Detector Experiment for Neutrinos

Think you can do better? Go ahead. My older son, a high-priced management consultant, offered another one pro bono: NEutrino Research DetectorS.

I am too young to have been in the room when ATLAS and CMS (or for that matter CDF and DZero) came into being, but last week I had the thrill of being part of something that had the solid vibe of history being made. The meeting website is here.

Joe Lykken, Fermilab deputy director


Day in the #PostdocLife

Tuesday, February 3rd, 2015

Recently, my wife, a.k.a. Polly Putnam, Collections Curator at Historic Royal Palaces, did a post for A Day in the Creative Life, a Tumblr page organized by the Department of Culture, Media, and Sport. So I thought I would borrow an idea from them and post about a day in my life. I’ve left the word “Creative” out of my own title, but it’s worth noting that scientific work is still very creative. I work every day on original ways to slice and dice data collected by the Compact Muon Solenoid (CMS) detector at CERN’s Large Hadron Collider (LHC); a lot of creative work goes into achieving that goal.

It’s also a team effort. As I go through the play-by-play of my day, you’ll see there are a lot of meetings and conversations and emails. Indeed, people often joke that CMS stands for Continuous Meeting Society! You might be tempted to see this as overly bureaucratic, but I hope to it will come across to you that the way we organize ourselves is a necessary approach to worldwide collaboration on one of the biggest of Big Science experiments there is. Just in a single day, the colleagues I interact directly with are in America, the UK, France, Switzerland, India, and China.

06:00 Wake up, in the darkness, slightly later than usual.

07:00 Out the door and warming up the car. Normally my wife would drive me to the train station, which is just across the river from the palace she works at, but today she’s at home and I’ll drive myself. This is scary, because most of the driving I’ve done in my life was on an automatic transmission in the United States — here, I have to deal with the clutch, drive on the left side of the road, and deal with far less space than I’m used to.

07:24 My first train leaves Hampton Court Station. I sit down and resume reading Seeing White, a textbook recommended by Harvard Astronomy Professor John Asher Johnson as a starting point for learning how to help address racial inequity in science and beyond. My trip involves changing trains once and a bit of a walk through London at the end.

08:30 I arrive at the office at Imperial College London and take stock of my day, especially the emails about the meeting I’m leading in 90 minutes.

09:00 Chat with colleagues about their contributions to the aforementioned meeting.

09:30 Throw together my own “news” slides outlining the status of the project and how people can help.

10:00 Go to a meeting room and “phone in” to the meeting I organize, where we work on preparing software for “Higgs to Gamma Gamma” — that is, to (re)discover and study the Higgs boson decaying into pairs of photons when LHC Run 2 starts this summer. I give my overview, others give more detailed talks on their progress, and we discuss what we need to do next.

11:00 Breathing a sigh of relief, I finally start on a bit of actual work for a new project I’m helping with. “Actual work” usually means, to me, writing and testing C++ code, although at the moment I’m also editing a wiki page so that colleagues can follow along with what I’ve figured it out. While my code is compiling I correspond with colleagues who want to contribute to my other project — informal discussion meetings are set up for tomorrow, which will also be “by phone.”

11:30 I grab a sandwich and eat it, along with delicious roast vegetable stew.

12:30 On “the phone” with another colleague, talking about handing off a coding task that I originally planned to start on but no longer have time for. After walking through what I know so far, I promise to help as needed with the details.

13:15 More interleaved emails and bits of coding.

14:30 I drop in on one of the academics I work with. As a senior postdoc, I do most of my work — and even help organize others’ work — mostly independently, but the overall priorities of CMS and my research group are set by more senior folks. I go to them with questions or just to check in about my overall progress and next steps.

14:40 Start a major edit of the instructions on my new project, testing each step as I go.

15:00 “Phone in” to the general Higgs to Gamma Gamma meeting. This is a broader meeting than the working meeting in the morning, where I can keep track of other work on analysis development and preparation for the next LHC run, as well as the analyses that continue on the data we already have.

15:03 Computer crashes. Reboot in a panic, phone back into meeting just in time for it to start.

15:20 Realize the instructions I was editing were lost in the reboot. Restart from where I last saved and repeat my work as I listen to presentations in the meeting.

17:00 After the meeting ends, I finish my documentation and check in with the person organizing that project. Check back in to help the colleague I talked to at 12:30.

17:45 Process an email with new code for the Higgs to Gamma Gamma analysis framework. Check that it works before adding it to the overall project.

18:05 Start going home. Have several train mishaps but eventually sneak on. Work on a bit of blogging when I finally get a seat.

19:15 Get off the train, get in the car, and go grocery shopping.

20:15 Supper. Couples’ Minecraft. Eventually, sleep.

And then I start it all again the next day.


Physicists frequently stray into the field of philosophy; notable examples include Thomas Kuhn (1922 –1996) and Henri Poincaré (1854 – 1912). This is perhaps because physicists frequently work in areas far removed from everyday experiences and, in order to be successful in communicating their ideas, underlying assumptions must be dealt with explicitly. Although less well known today than Kuhn and Poincaré, Percy Bridgman (1882 – 1961) also falls into this category. In physics, he is noted for his work on high-pressure physics, winning the Nobel Prize in 1946. In philosophy, he is credited with coining the term OPERATIONAL DEFINITION and promoting the idea of operationalism. These ideas are laid out in the 1927 book: THE LOGIC OF MODERN PHYSICS. If nothing else, it shows the folly of using MODERN in book titles. None-the-less, it is an interesting little book and, in its time, quite influential.

In his book, Bridgman introduces several interesting ideas, for example, that when one explores new areas in science, one should not be surprised that the supporting concepts have to change. Hence we should not be surprised when classical concepts fail in the relativistic or quantum domains. This illustrates why interpretations of quantum mechanics, explaining it terms of classical concepts, are poorly motivated. A related idea is that an explanation is the description of a given phenomenon in terms of familiar concepts.. Of course, with this definition, what qualifies as a valid explanation depends on what the explainee is familiar with. If one cannot succeed using established concepts, one must explain the new idea using familiar, albeit far removed, concepts But what happens when even this does not work? Bridgeman suggests that the solution is to introduce new concepts and become familiar with them. Seems reasonable to me. Thus quantum mechanics can be explained in terms of the, familiar to me, concept of the wave function; no need for many worlds and the like.

While it is natural to think of high speed (relativity) or small size (quantum mechanics) as new areas of science, Bridgman includes increased precision as well. He talks about the penumbra of uncertainty that surrounds all measurements and that is penetrated by increasing the precision of the measurements. Thus the idea of the distinct high-energy and precision frontiers, commonly discussed in modern particle physics planning exercises, goes back at least to 1927.

Bridgman was also a phenomenologist to the core. He did not believe that a priori knowledge could constrain what could happen; in his words: Experience is determined only by experience. C.I. Lewis (1983 – 1964) in his 1929 book Mind and the World-Order agrees. The similar ideas, in books of about the same time, indicate the concerns of that age.

Despite these interesting sidelights, the main idea in THE LOGIC OF MODERN PHYSICS is that concepts are defined by how they are measured; that is by the measurement operation, hence the term operationalism. So why was he interested in operational definitions? It was to avoid the problem in classical mechanics where concepts like distance and time were taken for granted. It then came as shock when the concepts proved to be rather complex when special relativity was invented. To avoid such shocks in the future, Bridgman proposed the idea of operational definitions. For example, to measure length you go down to the local Canadian Tire® store (in the USA it would be Walmart®), buy a tape measure and use it measure length. Thus the concept of length is defined by Canadian Tire®, oops, I mean by a tape measure. What if I measure length by surveying techniques that make use of tranquilization? Bridgman claimed that that is a distinctly different concept and is covered by the same term only for convenience. Here at TRIUMF, distance and location are also measured using laser tacking. This is again a different concept than the original concept of length. Things get even more complicated when we talk about the distance to stars which use again a different operation. Bridgman suggests that length loses it meaning at lengths less than the size the electron because such lengths cannot be measured. Today we would say they can be measured but length in that case is simply a parameter, in a mathematical formula, describing the scattering of particles. Hence we do not have one concept of length or distance but many, although they are the same numerically in regions where the techniques overlap.

Bridgman then goes on to consider various other concepts and how they might be defined operationally. He seems to have been very much influenced by Albert Einstein (1879 – 1955) and Einstein’s discussion of the synchronization of clocks (which actually goes back to Poincaré). The possible operational definitions of velocity are particularly interesting. In contradistinction to the definition given by Einstein based on clocks synchronized and distances measured in a fixed inertial frame, Bridgman suggests that the velocity of a car could also be defined by counting mileposts that the car passes to determine distance and using the clock on the car dashboard to measure time. This velocity can become infinite and would be useful to a person going to a distant solar system who is interested in how many of his years it takes to get there. For most purposes Einstein’s definition is more convenient and hence it is the one in textbooks though other definitions remain possible.

And on it goes. In some cases the definitions seemed quite forced. Never-the-less, three groups of people picked up on the idea of operational definitions. One group was the logical positivists. They tried to avoid theory and were pleased when a physicist gave definitions directly in terms of observables. The second group was the phycologists, who wanted a more secure foundation for their subject. The third group was in quality control and business management where Walter Shewhart (1891 – 1967) and Edwards Demming (1900 – 1993) adopted the idea.

However the concept, as the end all and be all of meaning, had its problems. Like logical positivism, it missed the idea that the meaning is in the model. While we may have different ways to measure length there is common idea behind them all. We can consider this common idea to be an abstraction from the different operational defined concepts or we can take the operational definitions as approximations to the abstract idea. One could say that operationally there is no difference between the two approaches.

Ultimately, operational definitions are useful. They tie concepts tightly to observations where they are less likely to be dislodged by future discoveries or new models. They also help eliminate fuzzy thinking. A lot of the concepts that do not have operational definitions are, in general, poorly defined. Who knows, I might even take the concept of scientific realism seriously if someone gave me an operational definition of it.

To receive a notice of my future posts and my pending book, In Defense of Scientism, follow me on Twitter: @musquod.


Art and science. They go together as well as general relativity and quantum mechanics, right? Or should that be Van Gogh and Rembrandt?

After reading that sentence, I’ll give you one guess as to which of the two categories I fall under – of course, ignoring the site the post is on! Yep, I’m a scientist and have been for almost 10 years. Life as a scientist is a focused tale of experiments, analysis and procrastination. I often ask myself – not just before a deadline – what else is going on in the world? Why not delve into the arts and see what’s new? I’ve been swimming (drowning) in science for longer than I can remember (that’s almost true, I have a terrible memory). It’ll be a breath of fresh air to see what the rest of the world is getting on with.

But how can I get a good experience? Sure, I’ve occasionally been to art galleries when they have their free open days, and both Google and Wikipedia provide satisfactory answers if you know for what to search, but I wanted something more engaging. Just like all good science solutions, an opportunity appeared when I least expected it.

A collaboration arose between the nearby Emily Carr University of Art + Design and TRIUMF in an attempt to collide the two disciplines into an incredible display of collaboration and creativity. And they needed help. My role in this collaboration was to bring the artists into our laboratory, show them our alchemy and schemes, and inspire them to take away from our tricks and sorcery something to entertain and brighten the world. In return, I connected with modern day art prodigies and experienced how they create art with inspiration from their surroundings. In my upbringing as a scientist, I also learned to appreciate the free cake and coffee on offer for everyone who took part!

We met and mingled for the first time on the tour of TRIUMF. Like Einstein showing up to a Turner prize ceremony (ignoring the obvious time impracticability), there was an air of confusion about how to interact amongst one another. As we gathered in the auditorium for the welcome talks, it was difficult to read the expressions on the faces of our artistic visitors. Were they confused or intrigued? Eager to learn or coerced into attending? The only way to find out was to jump in. Artists, welcome to my world of laser spectroscopy.

Off I start on explaining my work to the group, one moment speaking in too much detail, the next going too simple to overcompensate. The expressions start to change, but still I have no clue what they could mean. Proton-neutron interactions, angular momentum, electron energies, nuclear sizes, shapes; I throw out all of the good buzz words I know in an attempt to keep them interested. Sure the nods appear every now and then but as someone who’s been in more than enough conversations I’m not interested in, a nod can easily represent the deepest sign of disinterest. But then a hand pops up: “So, this is in relation to quantum mechanical behaviour?”…Yes, it is, but how do they know that? “Do you need to take into account any relativistic effects?” Erm…yes, we do, but I never thought about that until way into my work. “Does chaos theory come into any work here at TRIUMF?” Damn you artists! You’ve been playing me for a fool. You know way more about physics than you were letting on – well played. Ok, now we can start…


Engaging with the artists in the ISAC Experimental Hall at TRIUMF

Questions after questions fly in, all about the work we do at TRIUMF and almost anything under the sun they have read about science in their free time. They are putting me to shame; it is one-way traffic and I’m outnumbered. I barely know anything about the current state of affairs in the art world. Are they still showing animals chopped in half? Seriously, that’s all I’m aware of. And now they’re looking for ways to take what we’ve talked about and put them into projects they’re working on. Making sketches of equipment, taking photographs, recording ambient sounds and interviews.

It really was impressive to watch. Before we knew it the time had come for them to return to their world to create pieces born out of ideas created within our laboratory walls. I did not have the faintest idea of what to expect!

Was I satisfied with my venture into the art world? Had I ticked off artistic expression from my bucket list? Can I just return to solving physics questions that no one outside of physics is aware even exist? Of course not. This was my wake up call. Here are people moving forward with the work they are passionate about, but who also find time to take in the ripples of the world around them rather than hiding behind walls, unaware of theorizing tides until it overwhelms them. It will take a lot of work to observe and participate in the world around me, but I’m up for it, and no better time than to start than now. Or I could write a blog post about my experience and call it quits, tough call!

A few months after that project, I did in fact venture out again and found some of the pieces made by the group, showcased in a local exhibit at Science World (pictured below). I’ve included a selection of the pieces inspired by the artists’ trip to TRIUMF:


Science World, Vancouver BC




Full Moon by Richard Heikkilä-Sawan

“Full Moon is a multi-layered work that presents a dichotomy of chaos and order – a tension of opposites. Painted from the perspective of Earth, seven planets align themselves across the celestial sky amidst a storm of colour and black holes where every conceivable phenomenon appears to happen all at once. An undulating grid of iron strength brings a sense of calm as it gently rolls across the surface unaffected by the confusion that surrounds while appearing to collect a textured jumble of tangles and knots. Various shapes of colourful debris fly chaotically, bleeding off the edge of the linen on their frenzied journey through space – some visually represented by the mathematical implements that theoretically assisted in their creation. Full Moon explores the question, just where has that “giant leap” taken mankind?” – Richard Heikkilä-Sawan




The Lost Boy by Brigitta Kocsis

“Kocsis’ work investigates the shifting concepts of the human body and its environment. Contemporary discoveries in anatomical technologies have profoundly changed how one perceives the human body. The figures are like actors depicting a kind of abhorrent contemporary beauty where science fiction and artificial body parts are no longer fiction. The tension contained within the bodies of the characters due to pervasive technologies communicates the current environment in its fractured state.” – Brigitta Kocsis




All the flying saucers I have never seen by Glenda Bartosh

This is a typology that plays around with the “known” and the “unknowable” – both intrinsic qualities of scientific enquiry – and with ideas of verification and classification and their accepted limitations. I’ve used handwritten script and materials that echo old-fashioned field notes made by scientists years ago, especially during the 1950s and ‘60s when UFO sightings gripped the collective imagination. Personally, I haven’t seen any, so I couldn’t draw them, but flying saucers sightings are nonetheless organized into serious data banks. The typology is mounted impermanently on another organizing grid, reflecting how knowledge builds up in layers like a midden, sometimes burying and obscuring, sometimes building on previous knowledge – often based on the unknowable.” – Glenda Bartosh




The Snowflakes of Human Expression by Darren Andrychuk

“Through my work, I try to point out the brain’s potential errors in processing. This collage allows viewers to see those gaps in thinking. Most of my work can be interpreted in many different ways. There is no right message, but I always try to evoke emotion that open up the mind to other ways of thinking.” – Darren Andrychuk


–Tom, Postdoctoral Researcher at TRIUMF


DECam’s nearby discoveries

Monday, February 2nd, 2015

This article appeared in symmetry on Jan. 22, 2015.

The Dark Energy Camera does more than its name would lead you to believe. Image courtesy of NOAO

The Dark Energy Camera does more than its name would lead you to believe. Image courtesy of NOAO

The Dark Energy Camera, or DECam, peers deep into space from its mount on the 4-meter Victor Blanco Telescope high in the Chilean Andes.

Thirty percent of the camera’s observing time—about 105 nights per year—go to the team that built it: scientists working on the Dark Energy Survey.

Another small percentage of the year is spent on maintenance and upgrades to the telescope. So who else gets to use DECam? Dozens of other projects share its remaining time.

Many of them study objects far across the cosmos, but five of them investigate ones closer to home.

Overall, these five groups take up just 20 percent of the available time, but they’ve already taught us some interesting things about our planetary neighborhood and promise to tell us more in the future.

Far-out asteroids

Stony Brook University’s Aren Heinze and the University of Western Ontario’s Stanimir Metchev used DECam for four nights in early 2014 to search for unknown members of our solar system’s main asteroid belt, which sits between Mars and Jupiter.

To detect such faint objects, one needs to take a long exposure. However, the paths of these asteroids lie close enough to Earth that taking an exposure longer than a few minutes results in blurred images. Heinze and Metchev’s fix was to stack more than 100 images taken in less than two minutes each.

With this method, the team expects to measure the positions, motions and brightnesses of hundreds of main belt asteroids not seen before. They plan to release their survey results in late 2015, and an early partial analysis indicates they’ve already found hundreds of asteroids in a region smaller than DECam’s field of view—about 20 times the area of the full moon.

Whole new worlds

Scott Sheppard of the Carnegie Institution for Science in Washington DC and Chad Trujillo of Gemini Observatory in Hilo, Hawaii, use DECam to look for distant denizens of our solar system. The scientists have imaged the sky for two five-night stretches every year since November 2012.

Every night, the DECam’s sensitive 570-megapixel eye captures images of an area of sky totaling about 200 to 250 times the area of the full moon, returning to each field of view three times. Sheppard and Trujillo run the images from each night through software that tags everything that moves.

“We have to verify everything by eye,” Sheppard says. So they look through about 60 images a night, or 300 total from a perfect five-night observing run, a process that gives them a few dozen objects to study at Carnegie’s Magellan Telescope.

The scientists want to find worlds beyond Pluto and its brethren—a region called the Kuiper Belt, which lies some 30 to 50 astronomical units from the sun (compared to the Earth’s 1). On their first observing run, they caught one.

This new world, with the catalog name of 2012 VP113, comes as close as 80 astronomical units from the sun and journeys as far as 450. Along with Sedna, a minor planet discovered a decade ago, it is one of just two objects found in what was once thought of as a complete no man’s land.

Sheppard and Trujillo also have discovered another dwarf planet that is one of the top 10 brightest objects beyond Neptune, a new comet, and an asteroid that occasionally sprouts an unexpected tail of dust.

Mythical creatures

Northern Arizona University’s David Trilling and colleagues used the DECam for three nights in 2014 to look for “centaurs”—so called because they have characteristics of both asteroids and comets. Astronomers believe centaurs could be lost Kuiper Belt objects that now lie between Jupiter and Neptune.

Trilling’s team expects to find about 50 centaurs in a wide range of sizes. Because centaurs are nearer to the sun than Kuiper Belt objects, they are brighter and thus easier to observe. The scientists hope to learn more about the size distribution of Kuiper Belt objects by studying the sizes of centaurs. The group recently completed its observations and plan to report them later in 2015.

Next-door neighbors

Lori Allen of the National Optical Astronomy Observatory outside Tucson, Arizona, and her colleagues are looking for objects closer than 1.3 astronomical units from the sun. These near-Earth objects have orbits that can cross Earth’s—creating the potential for collision.

Allen’s team specializes in some of the least-studied NEOs: ones smaller than 50 meters across.

Even small NEOs can be destructive, as demonstrated by the February 2013 NEO that exploded above Chelyabinsk, Russia. The space rock was just 20 meters wide, but the shockwave from its blast shattered windows, which caused injuries to more than 1000 people.

In 2014, Allen’s team used the DECam for 10 nights. They have 20 more nights to use in 2015 and 2016.

They have yet to release specific findings from the survey’s first year, but the researchers say they have a handle of the distribution of NEOs down to just 10 meters wide. They also expect to discover about 100 NEOs the size of the one that exploded above Chelyabinsk.

Space waste

Most surveys looking for “space junk”—inactive satellites, parts of spacecraft and the like in orbit around the Earth—can see only pieces larger than about 20 centimeters. But there’s a lot more material out there.

How much is a question Patrick Seitzer of the University of Michigan and colleagues hope to answer. They used DECam to hunt for debris smaller than 10 centimeters, or the size of a smartphone, in geosynchronous orbit.

The astronomers need to capture at least four images of each piece of debris to determine its position, motion and brightness. This can tell them about the risk from small debris to satellites in geosynchronous orbit. Their results are scheduled for release in mid-2015.

Liz Kruesi