Quantum Diaries

My job at CERN has been to analize data from two different parts of the CMS detector. The DT (Drift Tube) chambers and the CSC (Cathode Strip Chambers) both measure the position of muons that go through the detector. The DTs are located in the barrel, while the CSCs are located in the endcaps of the detector. There is a region in CMS where the same muon can be detected by both systems. I am currently analyzing data from this region.
One of the first tasks that students who start working for a CERN project do is to get familiar with the software that is used here. In the case of the ATLAS detector, the packages that they use are all put together in a framework called ATHENA. At CMS, we use the CMSSW. It will take long before you learn how CMSSW works, and you have to be patient, unless you are very familiar with software development. Another package that students learn how to use is ROOT. You usually use ROOT for plotting the data that was obtained with the analysis done in the CMSSW.
Besides learning how to use the software used by the CMS collaboration, I have also been able to do shifts at the detector’s control room. This is located at P5 (Point 5) at Cessy, France. The control room is the place at ground level where each subsystem of CMS has its own station for monitoring what goes on. So people working on the CSC subsystem most of the time have someone monitoring the CSCs at the CSC station. The same is the case for the other subsystems. As a shifter, most of the time your job is to take runs (gather data) and to log them. Since there is always two shifters, one of them configures and starts the run, while the other one logs important information about the run. The detector is located 100m under this control room. If you have access to the detector cavern (or UXC55) you can go down and look at the actual detector. It is huge. I also had a chance to visit another detector, ALICE. This detector is a bit smaller in size, but still big enough to impress you. The cavern is 50m underground.
Living in France
I work at CERN on the Swiss side of the border. However, I live on the French side, in a small town named Saint Genis Poully. Saint Genis is a very calm place. There is a pub named Charly’s Pub that I visit with my roomates every once in a while. Other activities near Saint Genis include hiking to the mountains and paragliding. There is a lot of mountains in the area, and you can actually see the Swiss alps from CERN.
One thing you learn while living in Europe is that business usually close early. When my roomates and I need to buy groceries, we usually go to a store called Carrefour right after we get out of work. You can find Carrefour in many European countries, not just in France.
The Swiss city of Geneva is less than 10Km away from Saint Genis. It is really easy to get to Geneva from where I live, since all you have to do is take a road called Route de Meyrin. The CERN Meyrin site is located near Saint Genis along this road between Saint Genis and Geneva. There are nice places to visit in Geneva, such as the lake, or the United Nations building. If you want to travel to other European cities, all you have to do is go to the Geneva train station and buy a ticket. Paris is a little bit more than 3h away by train.

jafet

Hello, all.  This week my code finally went into production at CMS, and
it seems to work.  Hooray!  My little piece of the puzzle is some
monitoring code which tells the shifter whose job it is to guard the
pixel subdetector if a certain specific piece of the experiment is
malfunctioning in real time.  My boss, Dr. Karl Ecklund, wants me to
eventually add functionality to monitor other things, but for now, life
is good!

In other news, I've done some exploration of the surrounding area.
Lausanne and Montreux were very pretty, and I got to go hiking at a ski
resort called Les Diaberets, which was cool until it started raining, at
which point it became quite cold!  I also spent a weekend in Lyon, but
it was hot and not very interesting.

CERN in general is surrounded by beautiful scenery and filled with mad
scientists, but the infrastructure leaves something to be desired.  The
buildings look suspiciously like no architects were disturbed in their
construction, and the power grid needs some work!  Other than that
things seem cool.

More later,

Robert

Those of you who have been keeping up with the blogs will probably be aware that during the summer months, CERN has a summer student program that allows recently graduated students from all over the place – although most of them come from European universities – to come to CERN for a few months and obtain really valuable profesional and educational experience. The procedure to come here as a summer student is – as would be expected – highly selective; as many Physics and Engineering students apply. On top of that, this year the turnout of applicants was even higher given the present economic situation.

Although as Rice students we don’t strictly fall under the summer student program umbrella, we still mingle with them and naturally take part in the activities that CERN organizes for them. One of the most important ones – which I am finding extremely useful – is the Summer Student School Lecture series.

Every day, from 9 AM to Noon, they have three different lectures covering a wide range of topics – from the principles behind accelerator construction to Data Acquisition systems, passing through Anti-matter. The best part of them is that being at CERN, the lecturers themselves are all brilliant Physicists, some of the best in the world, who volunteer to give their time and effort to share a small piece of their knowledge with us. For instance, this week we’ve had the honor to receive Dr. Graham Ross, from Oxford University, who has given us five classes on the fundamentals of particle physics and the standard model. For me it has been very enlightening, as well as helpful seeing as one of the classes I’m taking next semester is Introduction to Nuclear and Particle Physics! Admittedly, the level of the lecture was maybe slightly above the level of lectures I am used to, seeing as it was aimed at new Graduate students and not undergraduates, but it is very difficult to homogenize the level of these lectures such that they are accesible (not too easy and not too hard) for everyone in such a diverse audience.

I’d like to share a little experience regarding one of the lectures that we had last week, even though it wasn’t one of the lectures from the Summer Student program. Dr. Steven Weinberg, the 1979 Nobel Prize winner in Physics, was at CERN last week to share his knowledge on Quantum Field Theory. All of the summer students happily marched (or more accurately ran, seeing as the seating was limited) to The Globe, the famous building that has now been immortalized by the Angels and Demons movie. I invite you to see the video of his lecture here.

You will see that a presentation of the most recent advances in the field of theoretical Physics hardly qualifies as “accesible”, as was evident from about the 2nd line of the 2nd slide. Amram and I didn’t really follow much of the content of the lecture itself, but it was still really enlightening. James joked while the first slide was up (where an unlabeled and handrawn simple graph was displayed) about how easily they give away Nobel prizes these days, anyone can make a graph like that! (again, refer to the presentation to see what is meant). And Vesna, my supervisor (and a PostDoc student) asked me to please summarize the lecture to her after it was done, to see if I had caught the minor details. We all laughed, seeing as I’m (hopefully) about 7 years away in my Physics education from being able to do stuff like that. The next day, even one of the lecturers from the Summer lectures themselves joked about how difficult it was to follow! However, it was great that we had the chance to go to the lecture and to listen to such a brilliant man speaking about what he is, well, brilliant at.

– Diego

There are thousands of different roles here at CERN, and my role this summer is coding.  I work specifically on the Pixel detector.  This essential part of CMS tracks the movement of charged particles passing through the silicon that comprises the Pixel detector.  The specifics of how this works are rather interesting, and also rather complicated, but I’ll focus more on my role.

The developers of the Pixel detector have written code that automatically calibrates and configures the system.  This code varies the multitude of different settings, evaluates the performance of the Pixel detector under these settings, determines which of these provide the best results, and then configures the detector accordingly.  I have been asked by my advisor, Dr. Karl Ecklund, to add code to this calibration process.

Now, I have little experience coding.  Before completing my undergraduate education I worked for 5+ years at a high tech company.  During my years there I worked very closely with developers to resolve software problems.  However, regardless of how much I desired at the time to assist with writing code, they thought it best to allow the highly trained professionals do that part of the work.  That is not the case here at CERN, and perhaps is one of CERN’s most amazing attributes.

I have been given a task, one that I felt under-qualified for when I arrived.  Over the past month I have learned, little by little, the skills and tools necessary to complete my task.  I’m not quite all the way there yet, but I am getting closer each day.  I liken this experience to the “sink or swim” method of teaching.  Sometimes I feel like I am sinking, I might have even drowned once or twice.  Other times I feel like I am soaring, although a new problem surfaces that sends me plummeting back towards the water.  Regardless, I am learning more about the ins and outs of coding in mere months, then I did in five years at a software development company.  All of this has been possible due to the culture here at CERN.

I must say I am enjoying my time here, and I am learning many new things.  The landscapes that surround CERN are quite amazing, and Geneva is a pretty nice city (though I don’t spend much time there).  The people I’ve met are friendly, and having the opportunity to explore different places in Europe is wonderful.   I won’t say that I don’t miss home, but who needs a Texas summer anyway?

James Zabel

So as my internship was drawing to a close (already…?) I was looking back on what I’ve been doing over the past month and a half… and a strange paradox made itself instantly clear: I feel like I still know very little (~nothing) about what is going on at the experiment, and yet if I were to travel back in time to a month and a half ago to talk to myself about what I had done and what I knew of the experiment, my past self would’ve been impressed at everything my present self knows. I guess that’s how you can tell how steep the learning curve is, and at CERN, when you’re working everyday alongside some of the most brilliant people in the world, qualifying the learning curve as “very steep” already sounds like a euphemism.

Yet learning isn’t the only thing I had going for me all this time. My professors would no doubt be relieved to know that I also did (some) work for the experiment, from taking shifts to mounting, installing and databasing (for lack of a better word I made one up) temperature sensors. You know you’ve got something good going for you when, as you’re fighting to get that sensor installed in the midst of all those high voltage cables and razor sharp scraps of hard nylon and metal (there is a mortality rate for undergrads at CERN… though that information is classified), some average Joe on tour of the experiment decides to take a picture of you as you’re working and even asks his kid to stand in the picture with you. I guess they should’ve given me a nametag with “the summer student intern in his natural habitat” written on it… (A “no pictures please, it bothers the animals” sign would’ve been nice too)

I also got some pretty interesting questions asked to me about the experiment. You get all sorts of people on these tours, but I really want to share an excerpt from a particular conversation I had with an anonymous man while touring my own father around the CMS cavern:

Visitor: “So I’ve heard that, if we discover this Higgs particle, also known as the “God” particle, then it will have proven the existence of the Divine Creator?”

Me: “Not exactly… only that there exists one particle that gives mass to all the other particles.”

Visitor: “But… that MUST mean that there is a God, right?”

Me: “I don’t know… is the Higgs particle mentioned anywhere in the Bible?”

(Imagine my shock when I learned that it wasn’t…)

And speaking of interesting people on tour, there was a very important official from the Vatican that came through the CMS experiment, and I heard that he asked where CERN kept its antimatter. We were also honored by the presence of Bill Gates at CMS, who, to my great disappointment, didn’t help us out with our software problems. Yet the greatest fiasco of all was the visit, in one day, of the presidents of Poland and Mozambique. That day, the farmer who owns the fields adjacent to Point 5 woke up with the sudden urge to spray manure all over his land, and, the wind blowing in the direction that it was, the whole place was a stinking mess for the duration of the tour of these two eminent visitors. I think next time the French will be pushing for EU subsidies for their agriculture, the Polish representative might have something to say…

Stinking-up foreign leaders aside, CERN is full of its own array of diplomatic incidents. Going into a physics group meeting, I didn’t expect to understand much, and I didn’t… at least, not physics. Because nothing, not even my professor’s constant references to the “heated debates” that took place within those meetings, could’ve prepared me for what I was about to witness: a yelling standoff between physicists arguing in favor of or against different theories (in keeping with my tradition of euphemisms, I chose to use the word “yelling“ to describe what was going on in that meeting…). To quote my own physics professor, Dr Padley: “It is interesting for you to go to those meetings not so much for the informational content they may have, but for the cultural experience as well.” I think I might disagree on the use of the word “cultural” there, though I will grant that I’ve never before heard so many curse words in all those different languages…

Yet that is what truly amazes me about CERN. It’s hard enough that they have ridiculously large amounts of data coming in, from different detectors, detecting collisions taking place in the largest scientific experiment in the world, operating at energies never before probed by man, but they’ve got to work together with scientists from all over the world! When this experiment finally operates at optimal performance, it will have been an achievement unparalleled in the scientific community, but also a tremendous achievement at the human level, and will confirm once more the resounding truth: that physics is universal, and though we may often disagree with the grammar, it nonetheless makes for one impressive international language.

Amram Bengio

One of the chores that we have to face as summer interns at the CMS experiment is the half-dreaded, half-loved shifts. During these at time endless periods of time, we get to drive about 30 km away from the LHC main site in Meyrin to the so called point 5, or the location of the LHC ring where the CMS experiment is, in the town of Cessy.

A shift involves monitoring the different subdetectors of the experiment, making sure that the temperatures, humidity, voltages and many other parameters stay within the specified ranges. As shifters, we have limited possibilities as to what exactly we can do to fix any problems that might (and do) arise. In case, we are to let the shift experts know about any issues that arise. Sometimes, the problems are trivial, and one must just make a note of them and let it go. However, as Amram and Tico know very well, sometimes serious issues arise, and one has to have the guts to take drastic decisions, such as turning off the detector itself. (Not that we have access to the buttons that do this, but we’re around when this is done).

Last week, for instance, there was a general power failure at point 5. Some of the cooling cycles did not turn on again after power came on, while some of the wires carrying thousands of volts were quickly heating up. Before they cooked, said voltages had to be turned off.

In general these events are quite rare though. It is of course necessary to always have someone controlling each of the subsystems (Data Acquisition, Tracker, Pixels, the different calorimeters, the cathode strip chambers…), because whenever the experiment is running,   someone will always have to on duty to check that the data acquisition process is running as smoothly as possible.However, spending 8 hours in a row sitting in a room with many screens, many of which don’t even change their display at all does get somewhat tedious at times…

Update: there is this cool website : http://cms.web.cern.ch/cms/Media/CMSeye/cam6.html. From there you can get a snapshot of the surface control room. It is updated every 5 minutes and if you’re lucky you might even see some of us there!

When we were first told to consider writing a blog entry for the US LHC Blog, none of us really thought much of the idea. However, after having discussed it together a little more seriously, we figured that if we could all contribute our fair share, it would not only be rewarding but also further the cause of helping people understand what it is that makes these massive physics experiments (like the Compact Muon Solenoid) tick.

So what exactly is a normal day for us at work? First off, each of us have different duties and responsibilities. In general, James, Robert, Jafet and Diego are more inclined to dealing with software. This means spending most of the day in front of a computer screen, remotely connected to offline servers that allow everyone at CERN access to essential computing tools and databases, but also allow us to enter a digital mainframe that all CERN workers share. Robert, for instance, has been working on a crafty bit of code that will warn us if something is going wrong in the internal circuitry of the Tracker detector (such as unexpected temperature changes) once the detector is running, and Diego has been working on reconstructing how the W bosons generated in certain proton – antiproton collisions decay into other particles. These tasks require a combination of understanding the subsystems of the detector on the one hand and the ability to interact with the virtual interface of these subsystems, which is why people like Robert (with his years of experience in the private sector) can be crucial components of the experiment.

Patrick (a.k.a. Tico) and Amram also interact with the CMS software to a certain extent, but they spend most of their time in “the cavern”, or the enormous underground hole where the monster particle detector lives. They get to install temperature detectors, or help out the technicians before the cavern is sealed (which should be happening very soon if all goes well). Being down there is truly an experience none of us will soon forget. The sheer size of CMS is breathtaking; but even more surprising is the endless intricacy and detail of it all. At first glance, it resembles more a piece of modern art than it does scientific equipment.

Stay tuned for more updates about how things go with us!