Tomorrow I will be packing up and leaving CERN to fly back home, after a quite eventful, productive, extenuating, exhilarating week. The reason for my coming to Geneva was the CMS week, an event that takes place four times a year, and where a good fraction of the members of our 2400-strong collaboration gather to listen to updates of the experiment, the detector, the analyses, and to discuss rules, appointments, organizational issues.

This time, though, there was quite something more to do here for me. Most of my students had also come to CERN, as well as some of the collaborators who work with us at one of the analyses I am following. And there were new data to look at! The Large Hadron Collider had just produced a small but noteworthy bounty of proton-proton collisions at 450 GeV and 2.36 TeV in CMS and ATLAS, and studying in detail these few thousands of events had become a huge priority.

Walking in the hall of Building 40 at CERN (above, in a panorama view), in the cafeteria, through the corridors, or around the buildings was different this time. Everybody seemed to be more active, walked faster, talked faster and more reservedly, busied themselves on their laptops. A place brimming with science in the making. Exciting!

So here are a few notes of my week at CERN. I will be unable to go into details of what I heard or did, but I nonetheless hope you will enjoy it and feel closer to the activities now ongoing...

Sunday - I arrive in the afternoon with a flight from Venice. Building 40 -the headquarters of the two main experiments- is not so empty as usual on a Sunday afternoon. And it is not due to the rain! People are working hard to produce the results that will be shown in the meetings this week. My students are not in the office, though. Maybe I am not tough enough as an advisor ?

Monday - I get to see some of the first results from the data, and I am excited to see that the detector is working like a charm! In the evening I start bugging my students and collaborators: we have data, it's there for us, we must run our algorithms and see whether we get this result, which I think nobody has yet tried to produce. Maybe it is too hard, maybe the data is too scarce to allow it, but we have to try!

They are convinced, and we start working like a single man. But the first results are unconvincing. However, I am astonished to realize that in the matter of thirty minutes, starting from scratch, we have managed to find the data files, produce a working piece of code, compile it, and run it on the data. The first histograms appear on our screens, and it is real data we are looking at! No more Monte Carlo simulations, the stuff we have studied for a decade or more now. The LHC is finally producing collisions in CMS, and from the data files stored to disk files to a meaningful histogram there is only a limited number of commands you have to type on your computer! Amazing, exciting, boosting our morale. But the result I have hoped to achieve is not there yet.

Tuesday - the day starts with a long string of meetings, which keeps me busy until the afternoon. But then, an email from Mario turns an average day into the brightest one: the mail has an attachment with the result I wanted! Mario has just applied one more cut on the quality of charged tracks reconstructed in the silicon detector, which was suggested to him by the tracking experts, and things have changed dramatically.

The histogram I have on my screen is showing something that testifies the quality of our detector, a result of no scientific importance now, but still an amazing display of performance, with so little data collected just a handful of hours before. And we got it first! We get together, work on the result for a while, refine it, and then we circulate it through an internal forum on the tracking performance. Soon everybody in CMS knows about it.

Yet, some of our collaborators still have doubts: is the result genuine ? Indeed, it is a surprise for most, and physicists are die-hard skeptics. We start receiving suggestions on how to really ensure that what we see is not caused by this or that effect or mishandling of the data. People also suggest to use a method to refine the result which we have tried all day to implement, but still failed. At seven thirty in the evening I call it a day, and join the rest of the CMS committee I am part of, for a dinner at a nice restaurant near CERN.

Wednesday - working on the method we have tried to implement in order to refine the result, we finally succeed. The further selection of the data retains the effect we have observed, making it more prominent, while the rejected data shows to be really background. This is a definitive proof that what we are seeing is what we claim. In the meantime, I follow more meetings, see and talk to people, get myself busy in a number of ways. The office I sit in crams half a dozen laptops and as many people, working elbow to elbow in a frenzy, some standing because there are no chairs for everybody: during CMS weeks overcrowding is the rule, but this time there is even more people around: every collaborator has apparently come to CERN, to hear about the performance of the detector on the first data!

The evening is spent at the CMS christmas party: 800 collaborators in a huge industrial building have gathered to chat, eat, and drink. The party is a success, I drink too much beer, and go home a little dizzy at midnight. As I crash on the bed, I am cheered up to know from the latest emails that my students and collaborators are still in front of their computers, to give the finishing touches to our plots. It is good to be the boss.

Thursday - I attend the plenary sessions, where the first physics results are discussed. And one of the talks includes the result we have produced just the day before! Luca, my hyperactive and sleepless Ph.D. student, is sitting next to me in the main auditorium. He nudges me when our figure gets up on the big screen, together with our names. And he is ecstatic when, at the end of the session, the spokesperson-elect spends himself in words of praise with him for our result, expressing surprise for such an early success. Luca, as well as Mario, have slept maybe ten hours in total in the course of the last three nights, but now they can see it was well worth it!

In summary, this was quite an eventful, exhilarating week indeed. But now all I need is a quiet weekend in the company of my kids!