Just a quicky-the CMS magnet ramps have started in the last few days – this is critical for us, since the last time we really turned on this magnet it was on the surface, about 2 years ago (nearly to the day!). Here’s the plot of the current (in Amps) versus time for the last few days – last night they reached 10 kA, about half of what they eventually plan to get to, but one does these sorts of things pedantically and carefully.  Keep in mind your house probably has 100 A service – so 10 kA is 100 Houses!  That’s a lot, but that’s the beauty of superconductivity.

I believe the plan is to go to 3/4 of full field this evening.   Soon all those event display pictures with tracks will be curving!

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Some folks working at CERN—I’m not going to single anyone out, but American taxpayers may be assured that it’s not anyone whose salary you cover—like to vacation for the entire month of August. Personally I’d rather be here working at this very exciting time, but now and then I do like to get out of town and enjoy all the places that are (relatively) easy to get to while I’m living in Europe. So I take a day or two off for long weekend trips now and then.

For example, this past weekend I was in Copenhagen, enjoying the lovely weather. (If you click for the large version of the image, you can see the raindrops!) I had a good time, but in order to get a flight I could afford, I had to (a) fly out of Zurich, and (b) return on Monday morning rather than Sunday night. That meant my commute to work on Monday looked like this:

5:00 am – Wake up
5:45 am – Catch subway to airport
8:15 am – Take off from Copenhagen
9:55 am – Land in Zurich
10:13 am – Catch train to Geneva (I had to run, but still, try getting out of an American airport that fast!)
1:15 pm – Arrive in Geneva, buy lunch at a pizza stand, and take the usual tram and bus to work
2:00 pm – Sit down at my desk at CERN

I stayed at work until almost ten to put in as full a day’s work as I could. (One of the great things about being a physicist in general, and a physics student in particular, is that you can put in whatever hours you like as long as the work gets done.) Of course, I was pretty tired, but what can I say? I like to work hard and play hard.

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Yes, been gone for far too long. July saw the arrival of my family in Geneve for a week, plus a move to new digs sans ethernet but with a great view:

Not having ethernet at home doesn’t bode well for blogging – I feel guilty writing when I should be working. But we got our 10 million channel detector working reasonably well, detecting Cosmic rays with the rest of CMS. This is a great step, but the Cosmic trigger rate is considerably less than what we expect at the LHC, so we still have to wait to see how well we’ll do with beam, and it won’t be too long now.

Then August, and a trip to Maine (Acadia NP) to get reacquainted with my family as well as some old friends from Fermilab who we used to go camping with, as described in my first blog appearance by a Quantum Diary writer. It’s pretty obvious who I am in the story. Anyway, 4.5 families of 4 in a house in Maine for a week, no ethernet or even cell coverage there, but we’re all still friends and had some really really good seafood. When I came back, I took my laptop in for repairs, as it did not run and charge at the same time, which added chaos into the normal work day for me. Well, 10 days, two motherboards, one keyboard, and a LCD display cable later it seems to have recovered, although again a week without my laptop doesn’t help the blogging (especially when my kids tie up the home computer during their laconic end of summer…)

But now I’m back, back at MIT, and will try to add my color commentary to the reports we get from those bloggers lucky enough to be there on the front lines. I’ll hop back and forth to Geneve a few times this fall, but in fact as others have mentioned it is very hard to predict exactly when beam will turn on – those who plan to go for “first beam” will probably be disapppointed due to some hiccup which pushes it just past the tenure of their stay. But it will come, of that I’m sure, and all indications are that the hiccups if any will be small. Meanwhile there is a fresh crop of yound and very enthusiastic students just coming in, and someone needs to teach them some Electromagnetism (it helps when your experiment has built the largest doorbell magnet in the world, though that’s not what we use it for…) so we’re off to a new semester.

The activity at the experiment is centered around being ready for the first collisions, the detector is closed up now (finally we cannot try to mess around with the 0.1% that isn’t working normally!  Striving for perfection can be a pain, and counterproductive as well!) and they are starting to run the magnet regularly.  You know how you feel when you are almost to the top of a very long roller coaster climb – anxious and excited about the ride ahead?  Hold on!

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Part of the LHCb detector was turned on during the recent LHC beam test, and they have some neat pictures of the first events recorded from the LHC here.

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If you haven’t already, check out Peter’s posting on the first findings of the LHC. He does a nice job of discussing the basic foundations we need to establish first before we can focus on the ’sexy’ physics; supersymmetry, the higgs, extra dimensions, etc. But before we can even do the studies that Peter mentions, we have to first calibrate and understand the detector. This in itself is no easy task.

Now that Sept 10th has been set as the day of first beam, the most frequent question I get these days is, ‘So, when are you going to see the higgs?’

I wish that I knew. But it is really impossible to put a timeline on something like this. So the answer is ‘I don’t know’. And if you are annoyed by physicists refusing to estimate when results will be ready, then you are not alone. I was speaking with a journalist earlier this week, who was clearly exasperated with me on this point. This was the gist of our conversation.

Journalist: What is the next milestone for ATLAS after first collisions?
Me: Once there are collisions, our next steps will be in the understanding of and the final calibration of the detector.
Journalist: And how long until that is finished and there are first results? A few hours?
Me: ATLAS has roughly 100 million electronics channels and nine different detector technologies. Calibration of that full system is incredibly complex.
Journalist: Two days?
Me: When we are satisfied that any detector-induced effects in the data are understood, we will confirm that we can observe the particles that we already know exist. Particles like the W and Z bosons.
Journalist: One week?
Me: Then we can be in a position to search for physics beyond the standard model.
Journalist: Two weeks?

In the mist of the first beam excitement, I hate to sound like a killjoy about the timeline for new physics results. But I think the focus is wrong. The next milestones for ATLAS might not be Higgs discovery but they are very exciting. Right now, even the background to the Higgs search is unknown to us. And as Peter mentions this is extremely interesting in its own right. So, who knows maybe by the time we are ready to search for the Higgs, it won’t be the most exciting particle in physics anymore….

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It’s a week full of ATLAS meetings here at CERN. This time it’s the “Performance and Physics Workshop”. The topics of the presentations are a mixture of some about the status of the detector/software, plans for what to do when we (very soon!) get first data, and studies of data analysis techniques or future improvements based on studies of simulated data.

The focus of these meetings, and really all ATLAS meetings, is shifting towards the data we will soon be recording. With more successful tests of beam in the LHC, the reality of collisions in the LHC is finally close. That makes the meetings these days a lot more interesting and urgent than a few years ago.
Thinking about meetings, I think there are mainly 2 times when meetings become interesting rather than just another place to bring your laptop to work:

1. When deadlines are approaching, like the accelerator turning on, or when a big conference is coming up and work needs to be completed in time. The few weeks before big conferences are always full of meetings to approve results. Sometimes there are even arguments, which makes them really interesting. People are very passionate when it comes time to put something out there in an official way.
2. When it is time to publish results. I have seen several arguments about how to interpret results, or whether something should be published at all, and even some shouting matches. This could happen if for example, there is a hint of a Higgs boson in the data, but not clear evidence. Should we put it out there, and risk it turning out to be a statistical fluctuation and not the real thing?

Well right now we have the first kind of interesting meetings, and hopefully soon after we will have the second kind, with lots of results to argue about.

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Some weeks ago, New York Times columnist Gail Collins wrote a piece about the possibility of black-hole production at the LHC.  I think she took this far too seriously; the chance of the LHC making black holes is super-tiny, and these aren’t the sort of black holes that are going to eat anything anyway.  Today Collins (who really is one of my favorite columnists, very trenchant political commentary) returned to the matter.  This time she did talk to an actual physicist, Brown’s Greg Landsberg, who is the US CMS physics coordinator.  She’s still too hung up on it, but at least she gave us some publicity for the big September 10 date, and even said that LHC startup will be as exciting as the upcoming Democratic and Republican conventions.  For sure, it will be more suspenseful!

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A Manchester physics student named Tim Head has created an amazing time-lapse movie of ATLAS being constructed, by putting together footage from the ATLAS webcam.  Experience in five minutes what we’ve experienced over the past five years!

See what Tim has to say about the video here.  If you like time-lapse ATLAS movies, there’s also a thirty second movie of one of the endcap toroids being lowered.

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Since I have been blogging for close to a year now, let’s summarize my topics.

In the control room, taking cosmics data
In the control room again taking cosmics data
Crazy athletic adventure
Control room, More cosmics
Control room, yet again
Control room, still
Control room, yes still
More crazy athletic adventures
Control room
Control room
Control room, what am I still doing here?
Euro Cup
Euro Cup
Euro Cup
Euro Cup
Euro Cup
Euro cup over, banished to control room again
Control room
Control room. Again
Control room. Again. Again.

So… I spend a lot of time in the control room. If you haven’t noticed. And needless to say I am in the control room while writing this. This comes as no surprise.

September 10th. This is the new ‘it’ date. On this day, single beam will run around the ring (and through ATLAS) for the first time. And every reporter on the planet will be there. Many of them in the ATLAS control room (which is why I am strategically staking claim on my control room chair now).

Now don’t get me wrong, I cannot WAIT for beam. The 10th can’t come soon enough. But after long days I tell myself, ‘you think you spend a lot of time in the control room now… wait until there is beam’…. But although I do love sleep. And although the prospect of getting sleep is pretty dim for the months of September, October and November, you couldn’t pay me enough to leave the control room. Not now. Not with first beam in our grasp.

So is it September 10th yet?
.
.
.
.
How about now?

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As Peter once noted, a contribution to Symmetry Magazine means a free blog post. Now it’s my turn; I wrote the commentary for the new issue, and here it is:

• Wikipedia needs more physicists

If you’re interested in contributing to physics articles on Wikipedia, WikiProject Physics is a good place to start. If you want to see what I’m up to on Wikipedia, you can look at my user page; bear in mind that my edits there are entirely my personal responsibility.

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The LHC startup is getting closer and closer. A few previous blog entries already informed you that there was a successful insertion of beam into the LHC. This is of course great news, but means that the testing and final preparations of the detectors has now become serious business. As the CMS pixel detector was planned to be installed as one of the final components before the first beam was delivered, we are very much under pressure to be ready in time. You can read that as ‘continuously on shift until things are stable enough to be run by non-experts’. This also explains the lack of blog entries by me and some of the other people working closely on the detector, at the moment the pressure is really on and the detector comes first!
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Indeed at 21:40 (GMT+1) on Aug 8, the first shot into the LHC made it all the way to IR3 – way to go!! One can probably say that there were no major polarity problems or big magnetic errors, miraculous and thanks to all those working hard in the tunnel installing and commissioning the sector. Hope the trend continues all around.

Later around 2 am one of the aperture tests being carried had caused a minor quench (remember 450GeV & very low intensity). Some access is taking place both from the accelerator side and ALICE. Should resume early afternoon and continue injection tests. Will investigate further and update.

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Beam in the LHC! A few of us were following the developments from the ATLAS control room. The comments on this screen shot from the LHC Operation Group web page say it all:

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It is like a fish market in the main control room now. Today, Aug 8, 2008 at 16:40 all the safety interlocks tests in the LHC were completed and the machine was fully closed for the first beam tests. However, it hasn’t without some small hickups, a fire alarm in the pre-injector (PS) and along with some other cabling problems, small panics before the big thing…

It is about 6pm now and they have managed to put the beam through the injector chain and all the way through the transfer line just 15 m before the LHC tunnel where it is stopped. The stopper in the transfer line will be removed shortly (6-8pm). The plan is to then adjust the timing of the injection magnets to put the beam into the LHC and thread the beam thereafter the sector 2-3 before midnight. Slightly optimistic but when you wake up tomorrow could the “first beam in the LHC” already be an old story ?

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In the recent mini-wave of “What Will We Find at the LHC” posts, no-one mentioned that the first actual measurements at the LHC will certainly not be of anything as exotic as the Higgs boson, supersymmetry, or large extra dimensions. This is not for any reason as prosaic as the fact that it’ll take time to get to the design energy and luminosity, which is true. If we define the very notion of “finding” something as being “measuring a quantity that we could not predict with current tools”, then the very first measurements at the LHC will count as discoveries of great interest to those not just focussed on what typically counts as exotic phenomena.

To boil it down to something concrete, consider the number of particles produced in a typical collision at the LHC. And to make things more straightforward, only consider the number of charged particles, the ones that leave curling tracks when moving through a magnetic field.
These are neat looking events, and they happen each and every time protons collide, at every energy, since the dawn of the accelerator era (you need a few GeV to even make a bunch of pions!). Thus, these particles are the “grass” that one sees in lego plots showing two huge jets, or the steel wool amidst which the two high energy muons emerge after a Higgs particle decays. For most people, this part of the collision is a background that needs to be cut away to see the interesting physics.

Here’s the rub: while it’s moderately easy to count the number of particles in each event, no-one has ever managed to come up with a bottom-up theoretical scheme by which one can predict this number. This is mainly due to the somewhat-scandalous situation that we know what protons “do” when they get close to each other (and can propagate that information into very precise predictions for the production of high pT particles, etc — the bread and butter of the LHC), but we don’t really get “why” they do it. Thus, we don’t have a very solid means to extrapolate our current knowledge into the LHC era, even if the Tevatron is only a factor of 7 lower in energy.

Thus, I promise that the first things you will see coming out of the LHC program are a bunch of measurements pertaining to “minimum bias” events, i.e. the events 99% of the experiment want to throw away so they can look for the needle in the haystack. Some of us (which include many of us directly interested in the heavy ion program at the LHC) want to see how the grass grows when those first collisions appear. We’ll count the particles emerging near 90 degrees, turn it into a “particle density” (by restricting the angle over which we count them), and put it on a plot with the rest of the data — probably with a few curves reflecting our favorite predictions. And everyone wants the first paper from the LHC, so it’ll be a real race, and so the results will appear almost as soon as real collision data is written to tape (which may well be this fall!)

For entertainment value, here’s my take.

This is a pretty straightforward application of the ancient (and bizarre) Landau hydrodynamical model to p+p minimum bias collisions and heavy ion collisions. It assumes that the two protons dump all of their energy into the collision as they overlap, and the system expands collectively like a relativistic fluid after that (sound familiar?). It describes the multiplicity (linear with the entropy) weirdly well for heavy ions (the top curve) above 20 GeV or so, and predicts a very high density at the LHC. It is pretty scratchy for p+p (the bottom curve — which may or may not be related to trigger bias issues — we’ll have to discuss that soon, too) but at least predicts something quite a bit higher than most popular models. But if this model has anything non-trivial to say about proton-proton collisions (something suggested by Landau and Fermi in the 1950’s, but which became controversial and even “heretical” during the rise of QCD, something I wrote about a few years ago), then we may have to start to take seriously the possibility that even small systems have “medium”-like aspects similar to what people already say about the QGP at RHIC. And how fun would that be?

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