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Archive for March, 2010

These are plots of the horizontal and vertical positions at CMS where collisions will be expected to happen.  They were measured from “beam gas” events by experts from the CMS Collaboration.  There is a small offset of about 100 microns in one of the directions.  This information is being passed to the LHC operators.   The moment of truth approaches, stay tuned….

Edgar Carrera (BU)



It is 6am at CERN and I am in the UK, remaining awake and looking out for anything interesting going on. This is a very different experience to when we first collided at 900 GeV and I was physically there, although my sleep levels are the same! I am hoping that if collisions happen in the next few hours, I can catch some footage and show any interested people later on today. I am a little jumpy as LHC have been playing around with both beams since around 5.15.I think it’s time for some tea.

If you want to follow what’s going on (as much as anyone not physically present can), try these links:

LHC Status

ALICE Live from the control room

ATLAS frequently updated event display

With these, be sure to refresh your browser. And of course what we will have at Birmingham in a few hours will be much better. Also, from 8.30 onwards, there is an LHC First Physics live webcast and ATLAS will have something similar streaming on their webpage.

ATLAS do have webcams in their ACR but they seem to be forbidden access to non-ATLAS members. Happy geeking 🙂


We will enjoy about one hour of stable non-colliding beams at 3.5 TeV.  When was the last time we saw all those indicators “true” and “green”?  It looks beautiful; congratulations LHC, and thanks!!….. we can’t wait for collisions!!

Edgar Carrera(BU)

lhc stable non-colliding beams at 3.5 TeV per beam

lhc stable non-colliding beams at 3.5 TeV per beam


Standby for 7 TeV Collisions

Monday, March 29th, 2010

We’ve been getting word that 7 TeV collisions are supposed to start happening tonight as early as 7 am at CERN (1 am Eastern standard time). As I’m writing the sign on the LHC Ops page is Beam Status: Ramp (the current energy is 480  GeV… no wait 500 GeV and rising 🙂 ). I’ll be watching the ATLAS control room live tonight (got the coffee pot going already)… but for those of you who want to watch too here’s a couple of links:

From the LHC control room. The webcast will start at 8:30 am at CERN (2:30 am Eastern).

From the ATLAS control room.

This one is already live streaming. Be on the look-out for my former roommate Stephanie, she’s run coordinator for the Liquid Argon Calorimeter tonight… and I’m sure she’ll appreciate me mentioning her in the post. I’m so jealous she’s there on the front lines. I know we’re all really nervous and hope everything goes well.

So tune in to watch!!!



Monday, March 29th, 2010

lhc1The first proton collisions at 7 TeV are supposed to happen tomorrow morning Geneva time – maybe just in time for people to be watching the morning news in Europe!

By the way, let me mention about the word “buckets” on the LHC beam status page.

Basically, the proton beams aren’t continuous – they are kept in tiny bunches or “buckets.”  The bunches in both beams go around the LHC ring at the same frequency and only cross at specific points.  So for protons to collide they have to be in synchronized buckets, or else they won’t be at the crossing point at the same time.

So keep an eye out, because soon, the LHC will be smashing together the world’s highest energy “buckets o’ protons”!


The next 24 hours are going to be critical for the LHC – the most challenging to date. They will make a first attempt to collide protons with 7 TeV centre of mass energy. This is far more than any accelerator has ever achieved, and it is not clear what we expect to find there. Physicists and engineers alike are about to leap into the unknown.

Last week I was in meetings at CERN finding out how prepared we are to deal with this uncertainty, and I took the opportunity to catch up with ALICE physicists and see how they were feeling. I spoke to experimentalists and theorists alike and it seems that there is no outcome we can’t be excited by. The theorists all have their own ideas – which contradict each other in measurable places – and many of the ideas on first glance seem to be completely mad. This is something I came across in the strange quark matter conference too, and if you look back on science’s history you can see that with every newly broken boundary in measurement comes wild, strange ideas to explain the unexpected, that are ridiculed and criticised and tested…and some are often surprisingly illuminated as the “uncomfortable truth”. This is a phrase that Johann Rafelski brought up with me over coffee last week and I like it, because it points to why these seemingly topsy turvy concepts have to be given the benefit of the doubt.

Since the recent release of Tim Burton’s take on Alice in Wonderland, I have been looking back over Carroll’s books and the ideas they conjured. It is not uncommon to look at “Through the looking glass” from a scientist’s perspective, as any wiki page will tell you (things like C-Parity or chirality and the idea of imperfect symmetries as an example) but the point that the first book (and indeed the film) really hits home is the idea that a little imagination or “madness” is desirable. “Believing as many as 6 impossible things before breakfast” may well be as good a practice for the budding scientist as developing a sense of criticism, because just as red herrings and ignorance hinder development, so does the refusal to accept the possibility of new, radical ideas despite the evidence to support them. Luckily for particle physics it is not lacking in imaginative physicists, and the best part about it is that they also can’t wait to prove their ideas wrong, which makes the whole process converge so nicely.

“Have I gone mad?”

“I’m afraid so, entirely bonkers. But let me tell you a secret. All the best people are.”

I have made a short video with interviews from the ALICE group describing their excitement for the coming days. There is nothing more thrilling to a scientist than the unknown. I may upload it to a resources page soon. For now though, I must go and prepare the Birmingham University Physics West Lecture room as a hub for live feeds to CERN, so that staff and students across campus can keep track of the developments tomorrow. If you want to keep an eye on what is happening, try here:



And of course, I am sure the news will be following the progress!


Marathons and sprints

Sunday, March 28th, 2010

I thought it best to write a post now, as I won’t have a chance to during this Tuesday’s excitement — not because I’ll be so wrapped up in first 7 TeV collisions, but because it’s going to be the first day of Passover, which will take me partially offline. (Who exactly thought that this would be a good day for the big event? Well, it had to be on some day or another.) Just like last time, I plan on sleeping through the big event, as I thoroughly expect it to be uneventful.

For instance, don’t expect any radically new science to emerge from the first days of collisions. While it appears that the experiments are really in excellent shape, based on the work done with the December collisions, it will take a long time to accumulate and analyze enough data before we can definitively say that we have observed any new physics. The amount of data we expect to take in these next two years is enough to make the LHC experiments competitive in discovering new phenomena, or constraining what new phenomena might look like, but that’s still two years worth of data. So, as the old saying goes, this is a marathon, not a sprint, and we have to pace ourselves.

But on the other hand, everyone is motivated to get out some kind of result as soon as possible, to demonstrate that the experiments do work and that we’ve got what it takes to complete the marathon. The major milestone is the International Conference on High Energy Physics, which starts on July 22. By then, everyone is hoping to have a bunch of real physics results (even if they are merely confirmation of known phenomena rather than discoveries) that can set the baseline for the performance of the experiments. July 22 is sixteen weeks from this Thursday. To go from having no data at all to high-quality measurements in sixteen weeks is going to be quite a feat. Put on top of that the uncertainty of just how well the LHC will perform over this time — by ICHEP, we definitely expect to have a million times as much data as we recorded in December. But it could turn out to be be ten million times as much! Whether any particular measurement is feasible or not could depend on which end of that range we end up on, and there might be many course corrections to make as we go along as a result.

So even though the real LHC physics program is a marathon, on your marks, get set….



Update (3/26): I should probably clarify that this post focuses on theories for new physics beyond the Standard Model. We certainly do have well-established theories that are absolutely spot-on within their regime of applicability, e.g. the Standard Model, quantum electrodynamics, general relativity… these have all been tested experimentally over and over and over again.

One our goals here on the US/LHC blog is to clarify a few public misconceptions about  physics. One thing that the popular press seems to get consistently wrong is that people are married to their models—by which I mean “plausible, but speculative, frameworks for explaining natural phenomena.”  Journalists will often write about a physicist’s pet model by starting with “Professor So-and-So believes that…,” as if Professor So-and-So goes to bed at night thinking of ways to explain to the world why his/her model is right and everyone else is wrong.

That’s not how science is done, not even speculative science. Just because someone spends some time developing a new idea, that doesn’t mean that they are doing so because they think it must be true. This may sound silly: if they don’t think its true, then why devote so much time to it?


One answer is that it could be true. Thus we should figure out what falsifiable implications it would have if it were true so that future experiments can cross it out. However, there’s a deeper reason to pursue ideas that one isn’t necessarily “married to.”

The point is that good ideas have value  just because they’re good ideas, even if they are necessarily speculative. Certainly a “good” idea should be plausible, e.g. a model of “intelligent falling” would have a very hard time garnering serious interest. However, there are plenty of good ideas out there for open questions. Of course we really want to find the “right ideas,” but there’s no way to know which ideas, if any, will ultimately be reflected in nature. All we can know are which ideas fit present data and which have strong theoretical (somewhat subjective) motivation. Rigorously exploring these ideas, their implications, and their inter-relationships allow the field to move forward.

[An interesting side note: it’s not even clear that there should be only one idea which is “right.” Much of the modern progress in theoretical physics is based on the idea of “dualities,” i.e. two totally different models describing the same physical phenomena in complementary ways.]

The value of “wrong” ideas is something that’s often under-appreciated in the popular press. In fact, theoretical physicists are usually interested in building up a tool-box of good ideas (independent of ‘correctness’ for a particular problem) that can be used as needed to solve open questions. One popular example is string theory.

  1. Our front-running speculative “theory of everything” wasn’t born with such grand aspirations: rather it was originally constructed as a potential model to explain the weird particles that were showing up at the old-school colliders of the 1960s. Later experiments showed that correct explanation (quantum chromodynamics) was something rather unrelated, and string theory (then known as “dual resonance models”) fell to the backs of everyone’s minds…
  2. … until some clever theorists realized that it could be used to give a quantum theory of gravity. This became a hip thing to study in the 80s and especially 90s, but since then has lost a bit of steam due in part to its lack of experimental predictions at accessible energies.
  3. But that’s okay: while people were playing with string theory as a “good speculative idea,” they discovered some very unexpected dualities between higher dimensional gravity theories (which are relatively well-understood) and lower dimensional models of strong coupling (which are notoriously difficult to work with). These ideas are usually referred to as the “holographic principle,” and have shown promise as models of, among other things, the very same kinds of particles that originally motivated string theory in the 1960s! (In coming full circle several new and rather deep insights were developed.)

Stories like this can be found all over the place in the history of physics. The extra dimensional models which became very popular in 1998 and 1999 are based on the Kaluza-Klein models from the 1920s, but adapted to solve new problems. The idea of electroweak symmetry breaking and a Higgs boson was built upon progress in understanding superconductivity. Good ideas never really die, they just lay dormant until the next big problem comes along.

In this sense, the measure of a theoretical physicist isn’t necessarily how many “right ideas” s/he has generated. (Indeed, in the past 30 years there hasn’t been enough experimental sources to definitively say anything about many good ideas.) Instead, the community values creative new ideas. And for what my two cents are worth, fostering this creativity—in multiple disciplines (arts, humanities, sciences, mathematics)—should be one of the main goals of primary and secondary education.

For what it’s worth, the ‘good idea’ that I personally think is most theoretically appealing is supersymmetry. But as evidenced by Cornell’s recent loss in the NCAA basketball tournament to #1 seeded Kentucky, most of the things that I cheer for don’t seem to benefit from my support. (PS, Big Red: we’re proud of you!)

Flip, US/LHC blog


Hi there!

The LHC is about to start colliding protons at 7 TeV (3.5 TeV per beam) or with about three times more energy than has ever been achieved by man. This is really exciting stuff! We’ll have a big media day on Tuesday to make sure everyone has a front row seat to the event!

Last night I was asked an interesting question – interesting enough that I thought I’d share the answer.

Will we collide the beams at many energies, or only at 7 TeV?

The LHC is really a discovery machine. Imagine that you’re back in 1490, and we’ve built a new ship that is capable of going seven times further than any previous ship in history before it needs to land (to refresh its stores, etc). The first thing we want to do with this is take it as far as it will go to see what’s out there! It could be that we’ll find a whole mess of new particles – that would be wonderful! It could be that we find nothing at all. That really would be like Columbus sailing for the new world and coming to the edge of the earth! It seems impossible and would fly in the face of everything we know – for physicists, it would be almost as interesting as finding a load of new particles! And, of course, when you’re sailing that far, you might pass some interesting things along the way…

End Of The Earth Images

Once you’ve searched for new high energy physics, you might want to try collisions at a few different energies. That would be something like looking for islands in the Atlantic. They might not be as exciting as a new continent, but they’re worth searching for all the same. Technically, just like if we were to sail out, we have no choice but to pass all the energies in between. But we do so for only a moment, and don’t really pause there to do any significant search in the middle. Side note: the middle energies aren’t quite as exciting at the LHC as they would be at, say LEP, because protons are “composite”, rather than single objects (as one professor put it, it’s like colliding two garbage cans). You can get some sense of what’s going on at lower energies from the higher energy collisions.

So on Tuesday, you should expect to see the beams go up from 450 GeV each (when they go into the machine) to 3500 GeV each (when they are colliding) without stopping in the middle – unless they plan something I don’t know about, of course!

One fun (very) technical note. Computers have a clock that keeps them in time (your computer is probably 2 GHz, for example). The whole LHC acts like a giant set of computers, all of which are timed together. It’s as though the entire thing has a single heart beat, around 40 MHz. We actually keep the heartbeat going at just the right pace to always have collisions “on time.” But the protons are changing energy from when they are injected at 450 GeV to when they collide at 3.5 TeV!! That means the entire heartbeat of the machine speeds up just a little bit to keep up (because of relativity, it’s only a fraction of a percent, but it is noticeable!!). To make sure things are safe, ATLAS usually stops collecting data while the heartbeat is actually changing – it’s a delicate operation, and we don’t want to have to stop to fix something right before the data arrives! So we may or may not actually see any of the collisions at energies between 900 GeV and 7 TeV!




One consequence of pursuing a career in science is moving house (often changing town, country, or even continent) several times, about every two to three years. While moving is always a hassle, one can also take it as a step towards a more essential lifestyle.
I had gone to university in Zurich, where I had grown up. When preparing to move to Berlin for my PhD, I had to face a giant closet full of clothes and stuff I had owned for 15 years, but likely not worn in the last 8. After I had thrown out a huge amount of things, I packed my boxes.
In Berlin, I started out with my first mistake. I went straight to IKEA and furnished my flat with just about everything I had seen in my mom’s house. I later discovered that the household of a grad student has different needs than that of a family. Most things I had bought (especially kitchen stuff) I have never used a single time.
What was a bit special in my case, was that after only one year, I had to move again, since my advisor moved to Munich. Given price levels for housing in Germany, my next flat was only half the size of the one I had had in Berlin. Consequence: most of my new furniture remained in Berlin and about half of the (still too numerous) clothing went to a second hand shop. Yet my new landlord claimed that no one had ever moved into their one-room flat with so much stuff. I became an expert in storing things in improbable places, like on top of cupboards, and under the bed.
Only two years later, I moved to Amsterdam. Another part of my furniture was left behind. I also realized that it was better to just stick with one kind of shampoo, conditioner, or body lotion, because moving five half-used bottles of each is a bit a waste of space. I learned to only buy new stuff when I actually needed it. And I learned to sort through my clothes regularly and give away what I don’t wear anymore.
After two years in Amsterdam, I moved to Japan. And it seemed smarter to use my moving allowance to actually buy what I needed new in Japan, instead of dragging my own (cheap) stuff to the other side of the globe. All remaining furniture and the last of my poor unused kitchen utensils found new owners in Amsterdam.
We arrived in Japan with four suitcases, and had three boxes shipped, that’s all. And this time, we did not make the same mistakes. In Japan, my husband and I only bought things for the household we actually found we had a need for. We know that we’ll have to move again in less than two years. So we bought inexpensive, but decent looking kitchenware and other household items that we can easily let go of when we are leaving. Of course we bought also some nice things that we will keep, for example our beautiful Japanese tea cups. But I think we’ll be leaving with almost as little as we came with.
All my moves, and the moves ahead, have taught me not to be so attached to stuff, because it weighs me down. I actually need rather few things, and the ones I do need for practical reasons, I am happy to use and then pass on. Like this, moving, and life in general, has become a little less troublesome.