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Archive for February, 2009

HEP, publishing, and open access

Thursday, February 26th, 2009

Last Friday night, fellow blogger Seth, some of our friends, and I had a discussion (with what David Foster Wallace called “that special intensity that comes after about the fourth beer”) about some interesting results from the CDF collaboration. After a while, the conversation wandered towards discussing the role of open repositories versus refereed journals. This is an issue of interest for science in general. However, high energy physics is an especially visible example of the contrasts between the two, because of our field’s reliance on a culture of preprints. To quote an interesting study (itself available on the open arXiv repository, established in 1991) on HEP publishing practices:

The preprint culture in HEP pioneered the free distribution of scientific results. For decades, theoretical physicists and scientific collaborations, eager to disseminate their findings in a way faster than the distribution of scholarly publications, printed and mailed hundreds, even thousands, of copies of their manuscripts before submitting them to peer-reviewed journals. This preprint culture tended, however, to favour the large laboratories and universities that could afford mailing large numbers of preprints while receiving comprehensive regular mailings. The spread of the Internet and the inception of the arXiv repository ushered a new era for the preprint culture, offering all scientists a level playing field. In its current implementation, arXiv allows researchers to submit their preprints and browse or receive regular feeds on recent submissions in their area of interest.

Open repositories like the arXiv have some major advantages over traditional refereed journals. The first and most obvious advantage is that access to the materials is free (at least to the end user). Instead of a costly journal subscription (which may run to many thousands per year), anyone with a working internet connection can download and read the results for themselves. Another key advantage is speed. Papers on the arXiv are instantly available around the world, which is important in a fast-moving and competitive field. The same results can take months to appear in refereed journals. And as author lists for large HEP collaborations swell, free electronic distribution avoids the high printing costs and page count of reprinting author lists with each paper1.



A kSteve

Wednesday, February 25th, 2009

As a proud member of Project Steve I am happy to hear and disperse the news that the kiloSteve milestone has been achieved, and in fact Steve #1000 is  Steven P. Darwin, a professor of ecology and evolutionary biology.  I am somewhere between Steve #200 and Steve #400 chronologically, according to the list of Steves , and joined back when I was at Yale – I have the 400 Steve tshirt to prove it.  As my good friend Steve Hahn (in my same range, probably just before me) was fond of saying:

You get three or more Steves together, and something wonderful happens

It happened a lot back on CDF for a while: There was Steve Chappa, Steve Hahn, Steve Kuhlman, Steve Levy, Steve Miller,  Steve Mrenna,  Steve Nahn, Steve Tether, Steve Vecjik and maybe I’m forgetting one or two, all in near proximity.  It was so dense you couldn’t move without bumping into someone named Steve, not to mention Stefano Belaforte, Stefano Torre, Stefano Moccia, and Stefano Giagu.

And yes, Steve Hahn’s name differs by one letter from mine, which occasionally created fairly humurous results (although he is actually a “ph” where as I am a “v”).  Some day I will relate the story of the two Michael Schmi(d/t)ts, but only in person.  There are two Bob Wagners too, “Argo” Bob, and “Fermi” Bob.  It got kinda surreal.


In Defense of Terminology

Tuesday, February 24th, 2009

Like many people, I’m a regular reader of xkcd. It’s funny almost half the time, which is a better rate than almost any comic except real classics like the Far Side or Calvin and Hobbes (and at least ten times better than Garfield). And, given my career and hobbies, it often brings up situations I react to strongly — and which may lead me into rants on related subjects even though I’m fully aware the original comic was just a joke. For example, here’s yesterday’s comic:

[Image from xkcd used under Creative Commons license]

I’ve seen Simple English Wikipedia before, but I didn’t look for very long: you can’t write very much about physics in it, at least not without going mad. The comic illustrates why very nicely: some ideas just can’t be conveyed accurately with simple words unless you use way too many of them. (Tiny things is not only simpler than particles, it’s also less specific. Are we talking about particles, or kittens?) We really need our terminology.

People don’t always differentiate between the words terminology and jargon — Wikipedia sometimes doesn’t, a fact that drives me nuts — but there’s an important difference. Jargon is what you make up to sound important, while terminology is what you need to describe things without turning a conversation into word salad. For example, let’s try to take the terminology out of this sentence:

An electron curves inside a magnetic field.

Which becomes, I guess:

A tiny electric thing from the outside of an atom curves inside a thing made by a magnet.

Or maybe this is close enough:

A tiny electric thing from the outside of an atom curves near a magnet.

But is magnet too technical? Electric? Atom? The solution in Simple English Wikipedia, to be fair, is to link to real terminology that’s truly needed. What differentiates terminology from jargon is that you’d rather define the word than remove it from the text, and physics is full of terminology. That’s what made this entry on tracking so long. I needed hit, track, momentum, energy, and other words to explain the topic, so I took my time going through them. And that’s the key to being comprehensible to non-experts: remove the jargon, keep the terminology, and explain it.


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?


LHC luminosity and energy

Saturday, February 21st, 2009

As Steve mentioned last week, the new LHC schedule for this year and next was revealed last Monday. The most prominent features of the announcement were the anticipated start date (autumn) and duration (one year) of the run. However, there were two other important parameters that were also discussed at the Chamonix meeting last week. We learned the luminosity and beam energy that the LHC team would try to achieve during the run. Both of these choices have important implications for the physics we can do with the data from the run.



Higgs Hunting News

Tuesday, February 17th, 2009

Physicists at the Tevatron made news at the AAAS meeting in Chicago by announcing an estimate of the chances of finding evidence for the Higgs boson at Fermilab in the next few years.  And they claim the chances are quite good, as you can see in the plot above.

The chances depend very strongly on the actual mass of the Higgs boson, which no one knows.  Depending on what the mass of the Higgs boson is, it will decay into other particles that are easier or harder for an experiment to detect.  So for example if the mass turns out to be about 170 GeV, the Tevatron experiments say their chances are almost 100 percent of finding it by 2011.  If the mass turns out to really be 135 GeV, the chances are below 30 percent.

The articles I’ve seen on this topic always play up the angle that the LHC and Tevatron teams are in a competition or race, which is definitely true to some extent.  But I for one am certainly not rooting against the Tevatron!

First of all, many people are part of both Tevatron and LHC experiments.  I, for example, was part of a Fermilab experiment, DZero, for about 7 years, and I would feel proud if DZero found the Higgs boson.  Second, all of us want to know if there is a Higgs boson and what it looks like, so to speak, and have wanted to know for a very long time.  If the Higgs boson is discovered, we will all be celebrating, no matter who discovers it.  Finally, there is plenty of great physics coming at the LHC that the Tevatron has no hope of doing, and wasn’t designed to do.  If the Higgs boson is found at the Tevatron, it doesn’t diminish the excitement of what is to come at the LHC.  If anything, it would make us more eager to see what else there is.  So I am rooting for the Tevatron!


Women in Physics

Friday, February 13th, 2009

Well, I am a bit leery of this potentially inflammatory subject, but this issue has been popping up with considerable frequency lately, including  Colette’s comment to new blogger Vivian (Hi Viv), a NYT article from some weeks ago, and a Physics division all hands meeting to try to brainstorm about what we can do to increase diversity within our ranks.  Yes indeed, the gender ratio of bloggers is not representative of the field.  I suppose this is true for all jobs which aren’t “9-5”, but in Physics it is apparently more pronounced.

Now, for fairly obvious reasons I do not feel like I have a reasonable appreciation for what creates this disparity.    There are some common reasons I think I at least can rationalize:

  • the pipeline: that culturally we have unconsciously swayed young women away from the hard sciences at a young age, so there just aren’t as many female candidates for advanced degrees and academic positions in Physics.  There is truth to this, but some inconsistencies too, mentioned in the NYT article.
  • the critical mass: potentially excellent female physicists are dissuaded from the field because they don’t want to be the only woman among coworkers-it is always lonely in the minority.
  • an MIT specialty- the firehose: success in this field is quite demanding, like drinking from a firehose, there is a deluge of things to deal with in a very short time – many hoops to jump through, lots of long hours, very little time for non-work pursuits, none of which is particularly conducive to family life, although I do not understand why this should have a gender specific effect.

There are probably others, but as I am not female, I am not really in a position to speculate.   I welcome suggestions.

If I think about my own situation, it is definitely true that my (wonderful) wife does the lion’s share of the child rearing tasks these days, and being away at CERN for multiple weeks at a time is not something I could do if she weren’t so flexible.  This seems to be the case for (almost?) all of my male peers with children- the spouses are typically at home or have flexible working hours and do most of the heavy lifting in terms of child care.    For married female peers, first, there aren’t a lot of statistics, that’s the point of this blog.  I know a few who have  solved the “two body” problem and have husbands also working a strenuous schedule, even some who work in different cities/states, but they do not have kids, and arrange to fly a lot to be together when schedules allow, etc.  I know less that do have children, and depend on a nanny/daycare for child care.  Still, those options require someone to be home at the end of the day and on weekends, which is not always possible for the aspiring physicist.

But here’s the real kicker, I guess: I cannot think of a single example of the opposite of my situation- the wife is working the time consuming job and the husband has the flexible job and does the child rearing.   Maybe there’s another “critical mass” which is lacking, and that is the “stay at home” Dad, so a woman is forced to choose between a less time consuming career and having kids, or going for that time consuming career and either finding that rare partner who takes on the role of primary child rearer, or ending up without kids.  (Note I am not saying there is anything wrong with not having kids, but my impression is that most of us have the expectation that we’ll have offspring at some point.)  It is certainly true that physicists tend to have kids late, (perhaps post-tenure? there’s  study for someone) – I know because I am the exception, with a 13 and 11 year old- the vast majority of my peers have kids ~5-8 years younger than mine, or more, and maybe that delay while the biological clock is still ticking plays a role as well?

I do know that both at MIT and in the field as a whole we are trying to do something about it.  The American Physics Society has a Committee on the Status of Women in Physics and a  Women in Physics program, which offers site visits to improve the climate for fostering women (and other minorities) in your department, and the results of a survey titled “Is your Graduate Department in Physics Female Friendly?” which 168 insitutions (including MIT) have responded to.  At MIT, the Physics Dept. supports both graduate women in physics and undergraduate women in physics groups, and in my own division 2 of the last 3 hires were women (who are also excellent physicists).  My point is that there is desire and effort to improve the situation, but exactly how to do that is not particularly clear, at least to me- part of the meeting today was to raise awareness and brainstorm a bit, so that was the straw that broke the camel’s back for writing this blog- you are invited to share your opinions (although we will censor with a conservative fist lest this turn into “the battle of the sexes“).



Friday, February 13th, 2009
During the Tom Hanks and Ron Howard visit to promote Angels and Demons at CERN were two Entertainment Tonight broadcasts (one last night and one tonight).  I just watched the one from last night online, and I thought it was pretty good.  Maybe my standards have been lowered after seeing so many bad accounts of CERN.  A few other physicists I talked to did cringe.  A few comments:
  • Tom Hanks has dubbed us “CERN-ites”
  • Tom Hanks asked “With the supercollider, can you reheat a cup of coffee?”

I respond, “Have you seen how much coffee the people here drink?  Do you think the coffee ever gets cold?”

  • Ron Howard said “Everythings’s practical, they’re not trying to put on a show here.”

Very true.  Maybe a polite way of saying that CERN is messy, but we can take it as a compliment.

  • Entertainment Tonight described antimatter as “a potentially volatile and lethal substance”, and CERN as “the top secret location where the antimatter is made”
Now I know this wasn’t a serious piece about CERN, but it’s frustratingly common for people commenting about CERN to suggest the research is somehow dangerous or has something to do with weapons. CERN is not at all top secret.  Anyone can visit, even movie stars!  All results are made public.  As for antimatter, nothing like what happens in the Angels and Demons book could happen in real life.  See CERN’s web page on Angels and Demons for some clarifications.
All in all, I suppose it’s good publicity for CERN and particle physics.  And it was a fun diversion from the long wait before collisions.

Beam is coming — Look busy!

Friday, February 13th, 2009

A lot has been written about the new LHC schedule. Like everyone here, I was deeply disappointed by the “incident” last year and I’m eagerly anticipating first collisions this year. Because of the delay in the collider schedule, my family thinks I’m on an extended vacation, but somehow I’m almost busier now than if we really were taking data.

As we wait for the accelerator repairs, my major focus is on managing one of the data analysis working groups. Actually maybe “facilitating” is the right word. My job is to make sure that the folks in our working group are ready to look at the first data with the CMS detector with all their software (and youthful enthusiasm!) revved up and ready to go. We do this using what we call “Monte Carlo Data” — which is a bit oxymoronic considering “Monte Carlo” means simulations of what we think LHC collisions will look like in our detector and “Data” implies the real signals from real LHC collisions.

The Monte Carlo “Data” is made in several steps:

Step 1 – Event Generation: In this step we generate a list of particles that might be created from a particular proton-proton collision. To do this we use the theory of Quantum Chromo-Dynamics (or QCD) combined with results from all previous High Energy Physics experiments to predict all the end products (particles) in an LHC proton-proton collision. This is (only!) our best guess of what the collisions will look like. There are many different “generators” for generating the final particles in a collision as we can only approximate QCD predictions and there are different models for how and what to approximate. Also there are a lot of input parameters to QCD (like particle masses for example) that have to be put in by hand. The output from the generation step is a list of all the particles from the collision, their charge, their direction and how fast they are traveling (i.e. momentum). Because in each collision there is only a probability for a particular set of final particles, we “roll the dice” and repeat the collision millions of time in order to get, on average, an idea of what the collisions look like. Hence the origin of the name “Monte Carlo”. Unfortunately knowing how to use a QCD Monte Carlo generator does not help you win at the gambling tables.

Step 2 – Simulation: Once we have a set of particles from Step 1, we simulate how the particles would interact in our detector. To do this we have to have a very complete implementation in software of our detector, including the positions of all the components and exactly what the signal from each type of particle would look like in each component.  Each part of the detector is designed to collect complementary signals from a particle. Even parts like the cables that bring signals from the inside of the detector out to the electronics that register the data have to be in the simulation since there is some probability that a particle will interact in the cables!

Step 3 – Reconstruction: In this step, we now forget we ever knew anything about the original generated particles and we try to reconstruct them given the signals we simulated in Step 2. This step we also perform on real data once we get it.

Step 4 – Calibration: From the reconstructed Monte Carlo events of Step 3, we can ask ourselves how well the reconstructed particle matches the particle we generated in Step 1. This gives us an idea of how well our detector will perform when we reconstruct real data (where we don’t know what the generated particles).

The better our simulation and reconstruction steps (steps 2 and 3) the more like real data our Monte Carlo will look like. The better our calibration step (Step 4) the better our understanding of the particles coming out of our real proton-proton collision will be.

Step 5 – Analysis: this is where we take the final calibrated collisions and look for all the cool stuff we hope to find like the Higgs boson or mini black holes. But most of the data will come from more mundane QCD processes, so in order to claim we see something new and different, we will have to work hard to make sure we understand the data in terms of our QCD generators (from Step 1). Likely we will have to do some tweaking of the generators since will be looking at hadron collisions at a much higher energy than anyone has ever before studied and we will have to modify some of our assumptions and approximations.

Right now, as we wait for the repairs to the LHC, we are busy creating millions of Monte Carlo collisions using different models for Step 1 and ever more precise detector information for Steps 2, 3 and 4. It’s a lot of work, but it will pay off in faster data analysis time once the real collisions begin. And I should mention that even though we think we are planning for all the eventualities in how the detector will react to particles from collisions, there are almost always surprises. So while we will see nice pictures of collisions at the instant they happen, it will take us longer to understand and analyze them.

So, in short, this is not much of a winter vacation. And I left out all the work we are doing repairing andimproving our own CMS detector while we have the opportunity during this down time!

P.S. I’m new to this whole blog thing, so please feel free to critique/ask questions/boo me off the stage…


Tom Hanks at CERN

Thursday, February 12th, 2009

At lunch today, I was told to look at the ATLAS Control Room Webcam to see actors doing some kind of publicity-related visit for the upcoming Angels and Demons movie. (I was sketchy on the details, because Thursday is the day that I try to practice French at lunch, and to me the French language has a certain je ne comprends rien.) Unfortunately, there was nothing to see on the webcam by the time I got back, but Stephanie Majewski saw the excitement, in person:

She has has an exclamation point in her title, and I don’t, because she actually got to see Tom Hanks. She has some other links with more information, and the Interactions News Wire has a blurb about this too.

So I actually don’t have much to say except to go read Stephanie’s entry. Yes, this is an archetypal example of writing a blog entry on the cheap, but I’ve had a rough week!