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Archive for November, 2008

Where ya been, Perfesser?

Tuesday, November 11th, 2008

Ok, Silence may be golden, but this is a bit ridiculous.  Truth is, right now I am back at MIT, busily teaching Electromagnetism to unsuspecting freshmen and upperclassmen who are onto me, giving presentations to Visiting Committees and preparing seminars which when scheduled had the promise of REAL BEAM DATA (see, you’re drooling too!)  but now fall into the category of “what we can do with zillions of cosmic rays” – is is unfair to pooh pooh the 300 million events CMS just collected, which are very useful for us as a dry run, but it just isn’t the same.

Being back here while everyone else is at CERN means I am a virtual presence, attending meetings in my PJs with a cup of coffee at my computer at 7 AM via VOIP, or occasionally getting to work in time to join by real video conference.  There was a surreal moment last week when Josh showed up using his laptop onboard camera:

Someone needs to recomplie his Kernel

No, he’s not from Australia – he claims he needs to recompile the Linux Kernel to get the camera to uninvert, but still, it is pretty strange to see such a thing so early in the morning.

Actually, funny enough, there has been some noise about blogging from the CMS management – apparently they are very concerned about physicists disparaging physicists, or “leaks” about LHC or about new results.  Now, I understand the concerns, but to me it also borders on censorship, and we professors feel pretty strongly about our intellectual freedom – anyway, maybe that is another reason for my lack of spouting off, but anyone who is worried about that ought to have a look at my second blog entry– it isn’t a real result unless it is in a peer reviewed journal.

So, I will continue to blog but if I  make anybody angry, let me know and we can discuss.  Discussion is good – sometimes I’ve had some pretty vigorous and loud ones, and usually I find all participants learn something (unless they are my 11 year old, who decides he isn’t going to learn anything even if it kills him which happens more often than I’d like).


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?


Counting experiments

Friday, November 7th, 2008

All measurements in particle physics ultimately come down to counting events.  How many events of type X did you see?  Of those, how many have property Y?  What fraction of X events did you miss because your detector is imperfect (it always is), and does that fraction have a dependence on Y?  How often does process Z come into your sample by accident, and does that too depend on Y?  It it through such careful counting, and then accounting, that we find the true production rates and true kinematic distributions, and use them to determine parameters of physical theories.

This week, the United States has been engaged in a set of really huge counting experiments — our federal elections!  According to the numbers I could find, something like 118.76 million people voted for either Barack Obama or John McCain in this year’s general election.  This election turned out to be not especially close, but some others did.  In particular, in the Minnesota Senate race, 1,211,542 people voted for Norm Coleman, and 1,211,206 voted for Al Franken.  That’s a 336-vote difference out of 2,422,748 votes cast for the two of them, 0.014%, and that’s not even worrying about the effects of independent candidate Dean Barkley (437,377).

Compare this to some of the most challenging measurements in particle physics:

W boson mass: 80.398 +- 0.025 GeV (0.031%)

Z boson mass: 91.1876 +- 0.0023 GeV (0.0025%)

Anomalous muon magnetic moment: (11659208 +- 6) x 10^(-10) (0.000051%)

Achieving this level of precision on these measurements has required many years and many graduate students.  And now we’re supposed to do the same in a matter of a few days to get the election results?  Good luck, Minnesota!


I’ve been thinking about it since this yesterday, and I’ve finally decided to take the plunge: I’m going to say a few words about the blogosphere debate on the CDF “ghost muon” paper.  I know that, by the demanding standards of the Internet, this is old news; the posts that started the mess were an eternity ago, last week.  In my defense, I have been traveling for the entire time, to Berlin and a few cities in Poland, in what now seems a confused blur of night trains and buses.  And in any case, I think my comments are universal enough that they’re worth making even if the debate is starting to die down.

I have relatively little to say about the paper itself, which was submitted last week but is not yet published.  Very briefly, the paper discusses a series of particle collisions seen by the CDF detector at the Tevatron Collider at Fermilab that appear to possibly contain muons which decayed from a very long-lived unknown particle — or maybe there’s a less dramatic explanation, and nobody’s figured it out yet exactly.  If you haven’t heard about this at all, I strongly recommend you go to Cosmic Variance for a more substantial summary.   One very big debate on the paper is whether it ought to have been submitted for publication in its present form; many experts who I know personally say that CDF should have been more careful in investigating the possible sources of the signal before publishing, and much of the CDF collaboration (including my colleagues at Berkeley) chose to take their names off of the paper’s author list.  The counter-argument, which won the day in the collaboration’s final decision, is that everything that could be done had been done, and that it was time to send the work out to the wider particle physics community to see if the signal could be understood and duplicated by other experiments.

A second “debate” is much more disturbing, centering on speculation that a group of theorists had written a new theory based on inside information from the paper before it was published.  When the group denied this, Tommaso Dorigo (who works on CDF and CMS) accused them point-blank of lying.  The exchange, originally in blog comments, is summarized here by Dr. Dorigo.  Although he qualifies his accusation a bit, he seems to stand by it and even reiterates it in the process of apologizing.

This kind of in-your-face accusation goes beyond the appropriate boundaries of professional discourse.  It seems to stem the bizarrely-prevalent idea that being really obnoxious in public is normal, as long as it’s on the Internet.  Would you, dear reader, put up a poster calling your boss an idiot, or give a newspaper interview in which you speculate that one of your coworkers is a liar?  No, you wouldn’t!  And nothing changes because our job happens to be physics, or the venue happens to be the World Wide Web.  Of course we all have the right to free speech, but what we choose to say has consequences; others have the right to choose whether or not to collaborate with me, whether at the personal level or the level of a large-scale experiment, and one thing they can and will think about is whether I’m going to publicly insult them.

One of the theory paper authors, Professor Nima Arkani-Hamed, wrote a several part response to these accusations, but one part of his comment really struck me.  It was about the physics blogosphere as a whole: he called it “brown muck” and said that he has “a very dim view of the physics blogosphere, and avoid[s] interacting with it.”  Upon reflection, this is a fair comment.  Many — though by no means all — of the physics blogs seem to spend a disturbing amount of time on personal “clashes” between “epic” personalities.  The ultimate example of this is found in the insults exchanged between Peter Woit and Lubos Motl, each of whom command large opposing followings (at least on the Internet) in the so-called “String Wars.”  The problem is that their extreme viewpoints and aggressive tactics don’t reflect what most physicists think about the issues; their drama, like these latest accusations about the ghost muons, is largely manufactured for consumption by the blogosphere.

I would like to think that the US/LHC Blogs offer a different vision, one that falls outside of Dr. Arkani-Hamed’s criticism.  We are, first and foremost, an outreach site.  We seek to explain the excitement of our work — the wonder of the Laws of Nature we’re trying to investigate, and the fantastic machines that we use for that investigation.  Of course we tell you about our lives in the process, to give you an understanding of what our work really involves.  We want to explain what our work means to you and why it’s worth your tax dollars, and we want to get young people excited about learning and maybe getting into careers in science.  Of course we also have interpersonal conflicts, nasty suspicions, and hallway rumors — just like anybody does — but in my opinion we’re not here to tell you about that stuff for two reasons: first, because all that nonsense is not what’s essential or exciting about our work, and second, because we owe our colleagues (and potential colleagues) the courtesy of not being rude to them in public.

I hope those of you who read our blog are looking for the stories that we think are important to tell; if not, sadly, it appears that you have a wealth of alternatives to choose from.  But I have been wondering about something, and in the words of Tommaso Dorigo, “I should like to open a poll for those heroic readers who came to the bottom of this post.”  Do you think all this infighting is valuable to know about?  Does it help the overall cause of expanding interest in, and knowledge about, our work?  (In fairness, Dorigo, Motl, and Woit are also known for writing very informative posts about subjects within their expertise.)  Or does the partisan warfare and discourtesy simply serve to distract readers seeking real knowledge?

You know my opinion on those questions, but I’d like to hear yours.  Until then, I’ll leave you with the words of Nima Arkani-Hamed: “I’m sure you’ll agree that there is more critical physics to do than there are hours in the day to do it, and I for one would like to get back to work.”


LHC in the news

Friday, November 7th, 2008

Even though there won’t be any discoveries for a while, the LHC remains in the news.  It was named the #5 best invention of 2008 by Time magazine.  Not bad, although looking at the top 4:

  • 1. The Retail DNA Test
  • 2. The Tesla Roadster
  • 3. The Lunar Reconnaissance Orbiter
  • 4. Hulu.com

I am a little disappointed.

Okay, at-home genetics (#1), electric cars (#2), and movie downloading web sites (#4) are more useful right now than the LHC, and space missions (#3) produce better images, but I don’t think any of them will have as large an impact long-term.

Although some people think the impact is already being felt.  When analyzing the election results on his comedy show, Stephen Colbert said (1:20 mark or so) he believed that the LHC “jolted us into a parallel universe that is exactly like our own, only Barack Obama is president and the Phillies are world champions.”  And he may be right.