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Vivian O'Dell | USLHC | USA

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Whatever Works

Sunday, March 29th, 2009

hystogramEarly on in my student career, I learned that a favorite excuse of physicists is that we are beholden to take “whatever works” in the task of describing Nature. Sure, sure, we do give some degree of greater weight to “beautiful” theories (some of us moreso than others), but on the whole we are a culture of pragmatists. We tease our mathematician compatriots rather a lot for lack of proper respect for a correspondence of theory to reality. And in front of an experimental physicist audience, it really is best not to talk too loudly about things that cannot be proven one way or the other by observation.

But don’t let the simplicity of “whatever works” fool you. I can’t imagine that any good physicist would actually be happy to accept and/or use a method that just so happens to predict reality, without some kind of deeper understanding of why it works, how far it can be pushed, and where it can break down. In fact I would dare to say that in the majority of experimental physics analyses, only a small fraction of the effort goes into performing the measurement itself, and the rest is spent chasing down and quantifying all the uncertainties one has to acknowledge about various aspects of the method.

What I find quite amazing is that every generation of physicist manages to be trained in the scientific method almost entirely by example. In Math one is taught the rules of deduction, and there is little ambiguity in what constitutes a valid mathematical proof starting from the axioms and down every link in the chain onwards to the hypothesis. There is no such uniformity in Physics; in fact, there may not even be any requirement that a physics graduate have any knowledge of formal logic. Now, I don’t mean to say that the Quod Erat Demonstrandum structure of Math is or should be equally applicable to Science. While one can use “A→B” in Math to show that B is true (after having shown that A is true), the same statement in Science is only good to whatever uncertainty — and, more importantly, whatever other “hidden” variables went into controlling the behavior of A, B, and A→B. If scientists tried to achieve as much formal rigor in their reasoning as mathematicians do, I’m not sure we would be able to make appreciable progress. And this is where another “whatever works” often comes in — even if unable to fully list and/or address all the issues in the scientific chain, one can hope to do something reasonable, and then check the answer against some kind of control region (a.k.a. lab test) in order to argue that it should work in the region of interest.

If you think that the above paragraph is cryptic and rambling, imagine trying to convey the hows of this thinking process to a student fresh out of classes, where all theories and experimental results have been neatly laid out, and even with exactly the required pieces of information, no more, no less. The actual process of research is nothing so linear or finite. A good researcher has to keep an eye on almost everything, because it is anybody’s guess as to what is necessary, important, or prone to breaking. And just because “whatever works” happens to work, does not mean that one  has demonstrated that it is not a lucky accident. And unfortunately, it seems like the burden of scientific proof is one of the most difficult things to learn in this apprenticeship.

[ On the very incomprehensible drawing : The grey blocks are a histogram. The red things are for you to interprete. The background is supposed to be waves, but apparently those are way outside of my technical ability. ]

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On the Utility of Super-Electrons

Monday, February 23rd, 2009

I don’t exactly have the least procrastination-free relationship with Life Beyond Physics. Ok, ok, so I’m the kind of person who wouldn’t mop the floor until I can see footprints on it. Bureaucratic documents? What is they? So long as the first lines don’t promise me incarceration and/or destitution, uhm, well…

However I must say that when EDF threatened to stop power from flowing into my home a couple of weeks ago, my response was immediate. What would I do if my computer won’t turn on? What will I eat? And — the first thought that entered my head — I really, really don’t want to chop firewood in order to bathe.

Having eventually persuaded EDF that they should take my money (really, I do insist), and resumed the life of a halfway normal physicist, I did spare a shudder for how duly proud we scientists are of the electron and how we squeezed this stuff called electricity out of it. It is such a well-behaved little particle — doesn’t break up no matter how hard it’s hit, easy to find, easy to manipulate, has a mathematically beautiful and complete theory, and wow, we actually get plenty of day-to-day use out of it! But in the meanwhile, we’ve gone on to decompose the universe into at least 16 types of particle fields, and one major ambition of the current generation is to find evidence of a “super-symmetric” mirror copy of the above Standard Model.

The LHC may very well find the super-electron. But this one will likely disintegrate before we so much as look at it, has eluded nearly half a decade of scrutiny, and the hypothetical model to which it belongs has so many unknowns that it’s pretty much a betting game as to where we should look. And if you were to ask me how far in the future I’d imagine humans might start using super-electrons in our not-so-daily lives, I can only think to quibble something about space-age and the indirect benefits of pure research.

A question for my phenomenologist counterparts — do we really need such a complicated (and growing) particle zoo to run life as we know it? Is it possible to have a universe with atoms and celestial bodies and maybe a few squishy organic beings, with only three fundamental particles just like we thought we had it all worked out, once upon a time?

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Brains Not Included

Friday, February 6th, 2009

2:15-hour skit for evening of 2009/02/06:

Sue Ann: Computer doesn’t have network support, problem is telephony service will not load without Blue Screen of Death.

MSTech: How are you today?

Sue Ann: Extremely frustrated.

MSTech: I am sorry to hear that.

—-[ Note to reader: Sue Ann does not need comforting, she needs a functional computer. ]—-
MSTech: Are you connecting from the machine that has the problem?

Sue Ann: That machine has no network.

MSTech: Please reinstall the display driver.

Sue Ann: Problem is telephony service. Display driver is working fine. Reinstalled anyway. Still crashing.

MSTech: Did you reinstall the display driver?

Sue Ann: Yes. It did not fix the telephony service.

MSTech: Please run this diagnostic tool and click on “send the result to M***”.

Sue Ann: That computer has no network. Your website to upload the file manually from another computer is broken.

MSTech: You just need to click on “send the result to Microsoft”.

Sue Ann: #*!&%$@##%

Synopsis: Sue Ann eradicated W*** from coffee table. Sue Ann installed U*** beta. There exists at least speculation that beta is more stable than the W*** product.

Moral: This may be why high energy physicists are often their own system admins.

p.s. I do still (or perhaps more so now) retain the greatest respect for the gurus who administer these huge computing farms and grids that are the backbone of modern experimental physics.

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Phase Transition

Monday, January 19th, 2009

I was very amused to read in the article “20 years of the W and Z bosons” (Physics World, vol 16 no. 1, Jan 2003) that CERN supposedly turned off heating to “make sure that the physicists took a Christmas vacation, and maybe even relaxed.” The motivations of upper management still remain obscure and elite, but heating certainly felt like it had been solidly off that first week I was back on the job. Now that the fingers are functioning again, some physicists have even started to do non-physics things like posting on blogs… but then, the same article mentioned that management “knew that many physicists would gladly freeze to death if they thought they would be able to get time on the computers,” ahem…

On the left: My home-town is by the city of Kuala Lumpur, 3°N 101°E — asian, tropical, and unapologetically unsophisticated in how it is alive. Having a number of loving parents ensures that I am volunteered for vacations.

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Life, The Universe, and Everything

Monday, December 8th, 2008

I don’t think any real scientist would ever make a statement like “this is impossible”, or “this will never happen” — it is always “this is extremely unlikely”, with a qualifying “if current knowledge and theory holds”. It seems to be a fundamental property of science that we can never prove that something is true, but can only falsify hypotheses.

So, what is this “no conceivable danger” conclusion in the 22-page “Review of the Safety of LHC Collisions” November 2008 publication by the LHC Safety Assessment Group? How does one make any claims at all about what will not happen in an unexplored regime of experiment/theory?

The fine print that resolves the dilemma is that “unexplored regime” is not true. Homo sapiens may be patting ourselves on our backs for finally anticipating life at 10 TeV center-of-mass energy, but the universe has been ahead for some number of years equal to 1031 LHC experiments — and at a rate of 1013 LHC’s per second. Now we note that the universe still exists (as far as we can tell), planets and stars don’t spontaneously turn into black holes (as far as we can tell), and even the Earth has apparently survived 100 000 LHC-like experiments i.e. all those cosmic rays that the cosmos bestows upon us.

Could the 100 001-st time be particularly unlucky? It’s not impossible, but we probably have to work much harder to increase our ratings as a threat to reality.

This post was inspired by an interesting comment from a reader, who asked “when will the experiment finish?” After getting all excited about the lifetime of CMS and proposed Super-LHC upgrades — and hitting the “send” button — I suddenly realized that the concern was probably “hey, when will you stop gambling with all our lives?”, and not so much “hey, how long does a cool experiment like this take?”

I was going to mention that I believe politicians and military to be more active threats to humanity than the unbounded (but not unregulated) curiosity of scientists. But then, it can be argued that destroying an ecosystem is still a lesser crime than annihilating the planet and perhaps the universe too, while we’re at it.

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Look, ma…

Friday, November 28th, 2008

I occasionally try to convince my decidedly non-academic family that scientists are in fact a subset of humanity, and not a pocket universe unto ourselves. Hey, we even have “vertical integration” meetings!

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Modus Operandi

Thursday, November 20th, 2008

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Que sera

Monday, November 10th, 2008

It is the end of autumn, and here at the footprints of the Alps it is easy to feel why the season has inspired poets and artists since time immemorial. The trees are well into their cross-dressing stage of red and gold, and still before the shabbiness of winter. Having grown up in the green plus green of the tropics, I find them glorious.

Life in the trenches of high energy physics analysis is somewhat less glamorous to the naked eye. We have our software ROOT, plus many, many, many trees of the data/simulation variety… I would be dishonest to omit that, some days, it is questionable as to which one of us is the being in charge.

Still, I think a sense of grandeur keeps us hanging on. However geologic the time-scale of experimental collider physics may be, it is more yet amazing to me that we manage to make any kind of claims at all. Every number seems incredibly hard-won, and plastered with so much fine print that I’d be surprised if any researcher ever listed them all. The undergraduate me used to think that Math was the more difficult field, but I now stand by that it is easier to be consistent with yourself, than to ask the Universe to be consistent with you.

So, I don’t typically have beautiful pictures of my work to pass around. I don’t expect discoveries here to improve agriculture, nor to impact manufacturing techniques within the next fifty years. My mother didn’t tell me that I would grow up to spend my days cursing at code; well, come to think of it, nor did my professors. But someday I will help coax a Statement or two out of the universe, and I hope it is one that will disturb and confound us greatly. How neat is that?

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the Quantum Field

Friday, October 3rd, 2008

the Quantum Field One of Michelangelo Mangano‘s lectures described how delivering kicks to a proton dislodges gluons from their otherwise invisible lives. Please note the ISR (Initial State Radiation) in this painting, which was also inspired by the quantum field theorists’ success in doing away with all those nice little Greek-style “atoms”; apparently, reality is now made up of identity-less “excitations” of some fundamental “stuff”.

In other words: Pending the repair of the LHC, some of the less immediately useful members of the collaboration (a.k.a. yours truly) has reverted to armchair philosophy and the occasional excursion into physics.

Or… not really. Do tell the boss that this blogger still remains:

  • a graduate student of UCSB
  • working hard (ahem) on triggers / dataset definitions plus whatnot
  • getting a Beyond Standard Model search ready for launch
  • (incidentally?) setting up groundwork for thesis
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