A Quantum Diaries Survivor

This morning LHC machinists, experimentalists from the LHC experiments, as well as other CERN personnel gathered in the Main Auditorium at CERN to give their end-of-year report. After a LHC status report the spokespersons of ALICE, ATLAS, CMS, LHCB, and TOTEM briefly flashed their first experimental results, obtained from 900 GeV and 2.36 TeV collisions acquired in the course of the last three weeks.

The signature of large missing energy and jets is arguably one of the most important avenues for the study of potential new physics signatures at today's hadron colliders. The above concept marks an interesting turn of events: the years of the glorification of charged leptons as the single most important tools for the discovery of rare production processes appears behind us. The W and Z discovery in 1983 by UA1 at CERN, or the top quark discovery by CDF and DZERO in 1995 at Fermilab, would have been impossible without the precise and clean detection of electrons and muons. However, with time we have understood that missing energy may be a more powerful tool for new discoveries.

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.

One of the cool things I have learned to do, through years of experience in data analysis at particle colliders, is to visualize the complex kinematics of a signal process in a multi-dimensional space, and imagine ways to separate it from backgrounds by selecting in the hyperspace the signal-rich region. I came across a very simple example of the above rather abstract statement yesterday, and I wish to share it with you.To help you visualize what I am going to discuss, here is the example: an avocado in a square tumbler. The avocado is top pair production, and the glass is Z plus b-antib production. ... Confused ? Let me explain.

I do not know about you, but top quarks fascinate me. Since my early years as a student in particle physics I participated in the top search, and then the top discovery, with the CDF experiment at the Tevatron collider; and I then worked for many more years with top quark samples. And that particle is fascinating for many different reasons: its phenomenology, the richness of its decays, its mass close to the scale of electroweak symmetry breaking. I feel honored by having had a chance to study the first few tens of top quark events that physicists have been able to produce, and yet I regret that during the last few years I have been unable to put my hands on the much larger datasets collected by the CDF experiment.

Tomorrow morning Venice will sink under a maximum tide predicted to reach 1.30 meters above average sea level. The event will occur at 8.35AM, a time when Venetian residents are in the streets trying to bring children to school or to reach their workplace. You can see the predicted evolution of the tide in the graph below, where the red curve shows the time variation of the season's average, and the blue one the actual prediction for tomorrow. The peak of 130 cm above average sea level is predicted to occur at 8.35AM -which is 2.35AM in New York, or 5.35PM in Tokyo.

This is the second part of a two-part collection of tips for particle physics graduate students. The first part is here.Three: be a fool today if you want to be a guru tomorrowThe third advice I have in store for Jane is maybe the toughest to follow, at least at first. But I do believe it is of critical importance for her to grow, become knowledgeable, and distinguish herself from the rest of the pack.

My blog is not a place for hot-off-the-press news - in it you are more likely to find discussions on material well digested and thought over. Nevertheless, I do not have the guts to sit on today's news. The Large Hadron Collider at CERN has produced its first high-energy proton-proton collisions, in the core of the experiments instrumenting its underground caverns.It has been a long way since the first design of this extraordinary machine. I was reminded of just how much effort the construction and commissioning took by a slide shown by Ives Sirois at a workshop in Turin today: it is a schedule of the construction of the LHC dated 1989!

Being a graduate student in particle physics is a tough, stressful job. I know it because I once was one, and I still remember the burden of giving exams, carrying on single-handedly a difficult analysis, and desperately struggling to learn the job of particle physicist, all the while trying to prove my worth to my colleagues. On the personal side, further trouble compounds the situation: one is usually fighting with tight money, stranded away from her family and boyfriend, and finds herself in the company of people whose similar priorities make the otherwise natural impulse of "having fun whenever possible" the last of their thoughts.

It happens in the best families, so they say. Two experiments work 24/7 to produce an improved result on the Higgs search, and the result is disappointing, to say the least.I am talking about the Tevatron, of course. For a little while longer, CDF and D0 will have the exclusive on Higgs boson searches. Last March, we all rejoyced when we saw that the Tevatron was starting to become sensitive to a high-mass Higgs, and indeed it excluded its existence in a range of masses between 160 and 170 GeV. We were waiting for more exclusions for the winter conferences of 2010, when more data would be used to produce improved results. Instead, no improvement, but actually, a retractatio. How is that possible ??

I recently discussed here the Tevatron results of searches for new Z bosons in electron-positron or dimuon samples collected by CDF and DZERO, pointing out that there seem to be a couple of intriguing upward fluctuations in the data. One of the dielectron fluctuations sits at a mass of 240 GeV, the other, also in the dielectron spectrum, is at about 720 GeV. Neither is compelling.

Last May the CDF collaboration published their observation of the  baryon, a particle made by a very exotic "bss" quark triplet. The CDF result came almost one year after a similar measurement was published by the competitor experiment, D0.