Tommaso Dorigo

Work in Progress

It is nice to see that, despite my lack of productivity these days, things are progressing steadily. It is the best part of having students working at projects you set up for them. While I am busy with writing proceedings for Moriond, making copies of papers I co-authored for a job application, and dealing with other silly things, my students are breaking ground.

Giorgio, who's in his last year of PhD studies, is giving the finishing touches to a very important new analysis (I wrote shortly about that here). Basically, he's found scores of top decay candidates that other analyses discard - for not triggering on them, or for applying too tight cuts on lepton identification, or for not looking at tau decay topologies -, and devised a method to compute backgrounds, such that he can claim he has 60 top events in a sample of 100 events. Now, the nice thing is that he is producing plots which demonstrate that those 100 events do have a component that's markedly top-like, in several discriminating distributions of kinematical quantities.

Marco, who's in his second year of PhD studies, has started producing interesting results on simulations of the pixel detector of CMS. The idea we're pursuing is of determining whether the pixels (tiny squares of silicon which record the passage of ionizing particles through them, thus allowing a very precise reconstruction of the particle path) can be used while triggering the events with jets, to save events with low jet energy from being discarded, if they are useful for extracting interesting physics signals.

Pietro, a undergraduate student, has started to study b-quark jets, to determine whether with the information available with the CDF tracker b-jets can be better measured (the energy is usually measured in the calorimeter, but if you know a jet originates from a b quark, you can use the information to your profit).

Andrea, another undergraduate student, is looking for J/psi candidates inside the jets of the events we are using to extract a Z->bb decay. B quarks can yield these interesting particles in their decay, through the reaction B->J/psi K. The J/psi is a very famous particle, and I think it deserves a post here, which I can only promise for now. In two words, it was its discovery in 1974 at Brookhaven and SLAC that provided the first unquestionable proof that quarks were not mere mathematical tools but real entities buried within the hadrons particle physicists studied day in and day out. It was like a earthquake in high energy physics, and today, 30 years from then, seeing a sharp peak from the decay J/psi-> mu mu (mu=muons, the heavier version of electrons) over a flat background is still an emotion, and counting these particles provides insight on the sample composition of our dataset, which is a valuable piece of information for our analysis.

Popemobile for sale

Would you buy a used car from this man ?

Well, I don't know if you would, but you sure can. In fact, Cardinal Ratzinger's used Golf (a black Golf, yes, the kind of car most used by young Casanovas in Europe) it is being auctioned on ebay.

It appears that the car used by Cardinal Ratzinger (now pope Benedetto XVI) has been put on ebay, with a base price of 9999.00 euro, by Reimund Halbe, a german citizen who probably used to ride Ratzinger around.  Halbe can provide written proof that the car was once used by Ratzinger himself. Hurry, I am sure you cannot get a better deal if you are a fervent Catholic.

Successful Diet

Three months ago I posted about the need of a new diet. As my most affectionate readers know, I lost nine kilograms (20 pounds) three years ago, and managed to more or less hold on to my optimal weight, around 72 kg (160 pounds) since then. However, if you look at my weight chart here, you notice that a slow rise has set on after the diet, such that early in 2005 I was up to an average of 75 kg (on the x axis the time is in days since June 2002, such that 1000 roughly equals mid March 2005).

I then decided to start a new diet, but for one reason or another I did not really begin seriously until I came back from the Moriond QCD conference, in mid March. Since then, my 1300 calories diet has scored successfully, allowing me to lose 0.1 kilograms per day, or three kilograms per month, as you can see from the set of points to the farthest right of the plot. I am now continuing the diet although I got back to 72 kg, since I want to get to 70 kg before I stop it this time. Time will be a good judge on whether I stuck successfully to my plan or not...

The Say of the Week

Groucho Marx: "So, Mrs. Smith, do you have any children?"
Mrs. Smith: "Yes, thirteen."
G.M.: "Thirteen! Good lord, isn't that a burden? "
S.: "Well, I love my husband. "
G.M.: "Lady, I love my cigar, but I take it out of my mouth once in a while!"

Physics Exhibit

Today is April 25th, and Italy celebrated the 60th anniversary of the liberation from the Nazifascists and Fascists. It is a national holiday, so no work today.

I should have been in a plane, since I have tickets in my hands for flying to Chicago this morning, returning then on the 28th back home. However, I decided not to go, since I have not recovered from the jet-lag from the previous trip yet. I am just too tired, and need some rest.

So today I could spend time with my kids. I brought Filippo to a Science exhibit in Ponte di Brenta, a small town next to Padova, where in a very nice palace (Villa Breda) tens of interactive experiments in Electrodynamics, Mechanics, Optics, plus Chemistry and Biology have been set up for people to try them out themselves. The pictures show the front of Villa Breda and the beautiful park behind it.

The exhibit, called "Sperimentando" (experimenting), is a success, as demonstrated by the many families with curious kids of all ages who crowded the rooms of the museum. The initiative is part of Padova's effort for the World Year of Physics, of course, as you can see in the web page of the exhibit.

Filippo was particularly impressed by the spark generator (a wheel which charges two large capacitors by friction, connected with two small conducting spheres that can be brought to a distance of about 1cm, yielding sparks as soon as the potential difference reaches about 30 kV). He also liked to peek in the many microscopes, showing paramecia and other niceties of the submillimeter world.

The best attraction of the day, however, was a demonstration of how to build and fly water rockets. Basically, you can build a rocket at home with plastic bottles of water or other pop glued together and provided with suitable wings and pointed top. You can then fill them for 1/3 with water, and then pump air inside with a regular hand pump for bycicles, until the pressure is enough to create a burst of water out of the only hole (where you pumped the air), projecting the missile up for tens of meters. They built three rockets of different dimensions. They all flew nicely, but the one that really awed the audience was the largest one, a 5 liter rocket built with three large bottles. It flew 200 feet in the air, then fell point first in the grass, ending like a nail on the ground. Spectacular!

busy and tired

I know. I've been posting very little this week, shame on me. Much less than the average for the QD site, and FAR less than my weekly average of about 5 posts.

What's up ? Well, although I cannot say I've been really sick, I have been sleep deprived for most of last week, due to a rotten combination of chronical jet-lag and Ilaria being unconvinced she has to stay in her bed at night. Since I insist on forcing her on her bed, I am the one who has to take care of getting her back to sleep when she wakes up in the middle of the night crying. But if my sleep is typically sound, and I am usually able to get back to it after  being woken up at 2AM, when I'm jet-lagged this is not the case!

All in all, my week has been spent trying to recover from the sleep deprivation of the first few days. Apart from that, undergrad students have taken most of my time, and a trip to Perugia on Thursday did the rest. More on that in the following post. Now I'm off to bed!

The Say of the Week

"I'm too shy to express my sexual needs except over the phone to people I don't know."

Garry Shandling

Sleep deprivation

Going back and forth on the two sides of the Atlantic is taking its toll. I'm in Italy since Saturday morning, and I've slept less than 10 hours total - including Friday and the flight back. That is about 3 hours a day, which is half of what I usually need. The problem has to do with Ilaria, which has now gotten accustomed to sleeping with Mariarosa, and is now in the process of being persuaded to stay back at her own place; and with my unavoidable jet-lag.

This blog also suffers from that, because when I'm sleep deprived everything becomes less interesting, more procrastinable, less compelling. Suddenly I'm not brilliant anymore. I speak by monosyllables, act rudely, even my kids fail to raise a smile on my face. Sex is nearly the only thing I can still do pretty well.

I'm looking forward to a good night of sleep tonight, but I know chances are it will be as the last few ones. But I have reacted in a sort of way to this. I canceled a trip to Fermilab in mid May. I still have to do the one to Fermilab next week, though - I have the tickets in my hands already, and they are two different tickets since they're interleaved. So next Monday, if I am able to catch up with the sun's rythm here, I will change it again, and then again on the following Friday when I'll be back here. In the meantime, this Wednesday I will have to drive to Perugia for a meeting of CMS physicists.

The life of a physicist may be interesting, but at times it does suck!

Flying back home

In thirty more minutes I will be heading towards the O'Hare airport, to fly back to Munich and then Venice, to my family for the weekend. This has been a productive and intense week, but this going back and forth over the Atlantic Ocean every second week is starting to get on my nerves... Please, Lufthansa, will you upgrade me to Business Class as you did last time ?

This time I'm flying back with a PhD student from Trento University. She is working with me at an analysis of top physics with tau leptons, and we'll have a lot to discuss together. But I need to also sleep, since tomorrow Filippo and Ilaria will require me to be at full power...

If I get to the business class I swear I will blog again from the plane. Lufthansa has wireless internet connection in the plane, but it is only worth doing it if you're in business class, because otherwise you don't have power and your batteries won't last for the whole flight... We'll see how it goes.

Being a bad guy and aching for it

The blessing process in our collaboration sucks, as I mentioned in a post here a few months ago. Blessing a physics result means getting approval from the collaboration to show it to the outside world - at a conference, in a paper, in a seminar. It may be painful to bless a result because you need to convince all your fellows that the result is sound, and even if you do people may object in the most obnoxious way to its publication.

I have always been on the side of taking it easy, being transparent, allowing results out even if they could be improved rather than forcing grad students to stay away from life for N more months because of the complaints of some sorry professor from an institutions 6 thousand miles away. However, yesterday I was on the opposite side of the trench.

It so happens that a very important analysis for CDF high-Pt physics program - I won't say which for privacy purposes - has been done in CDF and the results were up for blessing yesterday at the Exotics meeting - the meeting of a group which includes supersymmetry and Higgs analyses. The analysis finds an excess of 2.7 sigmas above background predictions. Still the proponents, not believing that is a real signal of an object that, if it exists and has the properties the Standard Model predicts, must yield much fewer events in our dataset, went ahead and placed a 95% confidence level limit on its production cross section.

Besides the obvious shortcomings of deciding to place a limit when you see a signal - admittedly not a compelling one - there is a big problem in publicizing such a result. Since we want to redo this analysis three years from now, when we will have collected enough statistics to be able to actually SEE the signal if we're lucky, then showing we do not understand the data at 2.7 sigma level now is a real mistake, which jeopardizes our ability to make claims in the future. More work is needed into trying to understand whether the excess of events observed is really a unlucky fluctuation or rather a systematic underestimation of our backgrounds.

Yesterday, I was not the only one to raise my voice against the blessing of these results. However, I certainly took a very active part in killing it. I pointed out that a statistical test done with the data had obviously wrong results, I complained that the dijet mass resolution is too poor to go proud of it, since it is 50% worse than what we publicized two years ago when we issued a report on the discovery reach of the Tevatron experiments for the sought particle, and I expressed my concerns with going public like this with a result that people will only take as our sign of defeat in this particular physics quest.

The analysis was not blessed, and more work is now required to bless it in a few months. I however feel bad, because one of the authors of the analysis is a friend of mine. He told me he did not take it personally and I believe him, but the guilt will stay with me for a while longer...