A Quantum Diaries Survivor

In a world where standing out is a good strategy in one’s life, in one’s job, in one’s way of living, I long to live in a normal country. The electoral campaign climax in Italy is approaching -elections are scheduled for April 13th-, and inevitably we start to see and hear things we would rather prefer to be spared.

Daniela Santanché, a charming and capable woman who self-proclaimed herself a candidate for premiership by the lone party from the extreme right she leads, declares today that she never had to make compromises for her career, adding -in case one could equivocate- that she never “gave it away” for personal interest. Given the fact that she later remarks she is actually more manly than most men, one is left wondering if she has ever really found herself in the condition of having to make that choice of integrity.

Silvio Berlusconi continues to mistify his observers by acting funny, this time making the “umbrella” with his arms in reposte [italics needed by established reader sensitivity to fancy terms, :o) ] to some offer he did not subscribe to. One is led to remember when he performed in two other pretty italian gestures: the “corna” (in a group picture with other european leaders, see below)

and the “dito medio” (middle finger) - see below.

If I had to make a prediction on the electoral outcome based only on the information above, I would say Berlusconi beats Santanché 3-0 (Veltroni, the candidate of the Democratic Party, does not qualify since he hasn’t said or done anything outrageous yet). Silvio Berlusconi is the one who can capture most brilliantly, with quick and sapient strokes, the essence of the average italian voter. A true Zelig, to which anybody can liken himself. Ms. Santanché, on the contrary, fails to realize that chastity and integrity are not valuable attributes in Italy nowadays: italians have learned the lesson far too well from their leaders of the past, and the perception that the country is divided in mettinculi (”a**-f***ers”) and piglinculi (”a**-givers”) is as vivid as ever.

I still have to see, though, a politician who admits he or she had to exchange sexual favors for a quick career. Now, that would be interesting. I have a feeling that the reaction of italian voters would then surprise everybody. Pierferdinando Casini should really consider that option.

UPDATE: Amara sent me a note on the meaning of the gesture of Berlusconi in the picture above. It is pasted below.

I am currently at CERN, where I am on shift for the CMS tracker (right). The CMS detector is in its final assembly phase, and the tracker - a cylindrical volume made by a dozen layers of silicon microstrip sensors- is being wired to its power, cooling, and readout systems. While this is being done, an important feedback can be given to the technicians by powering up the parts already wired and checking that everything is in good shape.

The microchips installed on silicon detectors in operation produce heat which, if not removed promptly and efficiently, causes overheating and eventually damage to the device. Because of that, one cannot power up the system without proper cooling in place. While the final cooling circuit is not operational yet, a temporary circuit of coolant has been installed on a part of a layer inside the tracker, such that we have a chance to spot problems connected to the assembling procedures early on.

Any temporary system requires a close babysitting. That is presently my job: as a SLIMOS (Shift Leader In Matters Of Safety) I am sitting in front of a desk in a control room inside the P5 cavern, 100 meters underground. I have to watch the temperature of the coolant, its pressure,  and take a walk to the detector hall to check periodically the dry air flowing in the system, the cooling pump and the flow circuits, plus the power supplies that run the modules we are testing.

The walk is the fun part of my job: even though I have not contributed in any way to the mechanical construction of the titanic project, I feel it as my own as I walk with steel-tip shoes through the maze of stairs and passages surrounding the detector, a hard hat on my head, a notebook and pen in my hands, and a professional look printed on my face.

Above you can see a part of the temporary cooling circuit that has been assembled to allow the powering up of layer 4 of the TIB (the tracker inner barrel). Pressure gauges, valves, and tubing - cool stuff! Every couple of hours they get checked up by the SLIMOS on duty.

Below instead you can see the graphs I have to keep an eye on during most of my shift. The temperature oscillates between 10 and 12 degrees during cooling cycles. Of course, an automated system is capable of alerting and shutting down the power to the sensors by itself, but in a temporary setup one has to be careful and oversee things: we do not want to burn our detector before it has a chance of seeing proton collisions!

So, if you watch closely, you can see that indeed, human intervention is required now and then. The jump up of the curves in the top graphs signals abnormal growths of temperature in the detectors being powered at about 12:17 hours today. Following the event, sensors were powered down with no trouble, but I then had to run and enable the power interlock and check the status of the cooling pump: the latter was showing an overpressure situation. I restarted it by following a 13-step idiot-proof procedure (in course of being updated!), and the system is now up and running smoothly again (as shown by the normal cycles on the right of the spike).

“There is a tragic flaw in our precious Constitution, and I don’t know what can be done to fix it. This is it: only nut cases want to be president“.

Kurt Vonnegut

(Seen in gravitas)

Enzo Boschi, a geophysicist in Bologna,  wrote about the issue of the appointment of Maiani as President of CNR. The themes of his letter funnily resemble those of on.Carlucci. I translated the letter below, but since it is quite long, let me first offer my executive summary in ten lines.

I wanted Maiani’s seat, and am pissed off he got it instead. I owe my career to Zichichi, who is a great, but really unlucky, physicist. I think Maiani, Cabibbo, Parisi, and the other physicists in Rome are overestimated, and I am a bit envious of their recognition, where Zichichi should instead be credited. I moved on to geophysics because of an earthquake in 1980, but I can’t explain what I did before then. I owe my career to Zichichi, and he is my teacher. I think writing a private letter to the rector of “La Sapienza” to disagree with the invitation of the pope equates to being delirious. Maybe my teacher Zichichi should have gotten Maiani’s seat instead. 

 Ok. Here is his text, in a very quick-and-dirty translation. I took the liberty to highlight a few passages which, in my opinion, reveal quite a bit about the motives behind the text. Oh, another important input. The text is titled “A note of purely scientific evaluation on the search for a president of CNR”. (more…)

Yesterday I wrote about on. Gabriella Carlucci, an ex-showgirl and now a politician for Forza Italia, Silvio Berlusconi’s party-company, and mentioned her failed occasion of shutting up when she insulted Luciano Maiani’s career in the Senate commission where the latter’s appointment was being discussed.

I have to thank Andrea Giammanco who pointed me to the blog of Pietro Folena (in italian), where the whole text of the infamous allegations by on.Carlucci is reported, along with an answer by none less than Nobel laureate Sheldon Glashow, who sent a indignant letter to italian premier Romano Prodi, expressing his disgust for the allegations of incompetence moved to a stellar scientist (his adjective) such as Maiani.

In the interest of disclosing just how far these dwarfs and dancers of the italian right will go to please their master, I paste below a translation of Carlucci’s statement, followed by the original text of Sheldon Glashow’s letter (more…)

The good news today is that a government decree cancels the insane rules of the Bossi-Fini law which made almost impossible for foreign students and research scholars to come to Italy for their studies. 

The decree (n. 17/2008) determines looser requirements for extra-UE citizens who seek to enter Italy. Accepting the european directive on the admission of citizens from extra-UE states for scientific purposes, the institutes will be able to obtain a visa for foreigners, avoiding lengthy bureaucracy and barrages.

Bossi and Fini, the first a xenophobe and the second an ex-fascist, cooked up a very restrictive law in 2002 as members of the Berlusconi government. The law dictated the procedure of expulsion of illegal foreigners or ones with no documents. It also made much tighter the legal admission of immigrants. It is this second part of the law which has partly been overruled today.  

Dwarfs and dancers, “Nani e ballerine”: this is the way italians call large incoherent aggregations designed to attract interest by their entertainment value. As the italian electoral campaign livens up, one sees definite trends in the formation of the main coalitions that seek a mandate to govern the country.

On one side we see the Democratic Party, whose leader Walter Veltroni bargained today an agreement with the Radicals, led by Emma Bonino (who is best known outside Italy as a former UE Commissioner for Humanitarian Aid, and is neither a dwarf nor a dancer), while showing the door to ex-DC Ciriaco De Mita, now 80 years old, after 45 years in the italian parliament -arguably, an expert dancer of the italian politics tango. De Mita takes offense, but a party which seeks to show some novelty in the political panorama cannot objectively rely on people like him. Instead, I salute as a very good idea the fact that 50% of the candidates for a seat in the italian parliament proposed in the lists of the democratic party will be women - but I remain a bit skeptical until I see that proposal materialize in a definitive electoral list.

On the other side the “Freedom Party” (Partito della Liberta’) led by Silvio Berlusconi made the news today by offering a candidacy to Aida Jespica, the supermodel and showgirl (see left). Jespica declines, saying she is not interested in italian politics. But worry not: we are going to see more dwarfs and dancers joining the electoral lists of PdL.

Showmen and women, singers, soccer players - there is a place for everybody, a big smile and a camera-ready face the only requisites. I still have in my mind the words of Gabriella Carlucci (right), a showgirl elected last time in Forza Italia (Berlusconi’s own party-company), who recently had the guts to oppose to the appointment of Luciano Maiani as President of CNR, openly criticizing his scientific curriculum: a good example of a failed occasion to shut up. How dare these dwarfs and dancers express a judgement on one of our best scientists ?

The D0 collaboration has recently submitted for publication a new measurement of the inclusive jet cross section, using 0.7/fb of integrated luminosity of 1.96 TeV proton-antiproton collisions collected during Run II at the Tevatron collider. I wish to summarize the results of this new precise analysis here, but before I do, allow me to explain why this measurement is interesting.

When you collide a proton with an antiproton (or, for that matter, any other hadron) the most likely result is that they scatter one off the other without breaking apart, and exchange only a small fraction of their energy: they practically fly one across the other, retaining their integrity.

However, hadrons are composite objects made of quarks and gluons, and sometimes a collision does involve a close encounter between a pair of those constituents. They may thus get kicked off the hadron with high energy. But quarks and gluons feel the strong force, which binds them to the hadron they belong to with a potential which grows linearly with their separation from it. As they fly away (in the horizontal direction in the picture on the right) recalled back by the strong force they decelerate, pulling a string of gluons as a bunjee jumper stretches the rubber cord he is attached to. If they have been kicked with enough energy the string eventually breaks, releasing its energy in the form of a new pair of quarks (the antiblue-yellow one on top, and then the antired-blue and antiyellow-red one below).

The process described above continues until a stream of partons (this is the generic way we call both quarks and gluons when we only care about the strong force) moving roughly in the direction of the original one is created. This fragmentation ultimately produces hadrons -the circles each containing a colored-anticolored quark pair in the pic above-, because quarks and antiquarks bind together into colorless objects. The electrically charged ones can be individually tracked with modern detectors, while neutral ones are harder to measure; but they are more meaningfully described collectively in what we call a hadronic jet - or simply, a jet. By measuring the total energy of the jet, and its direction, one gains access to the kinematical characteristics of the quark or gluon which originated it.

Measuring a hadronic jet is not that difficult: the energy of both charged and neutral hadrons in fact can be determined by letting them traverse our calorimeters: sandwiches of thick slabs of dense material alternated with plastic scintillator or similar active detector components, where they create new interactions, produce streams of secondaries, and ultimately get absorbed. The process has a negligible effect in terms of macroscopic quantities: a 100 GeV proton brought to rest by a block of iron produces in it an increase in temperature of about a picodegree Celsius (a thousandth of a billionth of a degree Celsius). We rather rely on microscopic effects: the scintillation light from all the secondary charged tracks traversing the plastic material produces a signal proportional to energy in a very localized region of the solid angle surrounding the point where the collision took place.

In the figure, you see a cartoon showing the different phases of a jet formation and detection: the proton-antiproton collision produces two quarks emitted at large angle with respect to the beam; a quark then fragments into hadrons; and finally, hadrons interact in the calorimeter, getting destroyed by the interactions with the material, and producing a measurement of the originating parton.

Once we measure a jet’s energy and direction we can do wonderful things: for instance, we can study the relative frequency of collisions as a function of energy and angle. We thus find that more energetic collisions are increasingly less frequent. By comparing the functional dependence with a model of the proton, we are able to test how well we know the proton structure.

And indeed, we do understand the structure of the proton amazingly well, after forty years of deep-inelastic scattering and hadron collisions. We describe what’s in a proton with Parton Distribution Functions (PDF): functional forms , , …, that tell us how likely it is to find inside an energetic proton a quark of a given kind (u,d, …), or a gluon, carrying a definite fraction of the proton’s energy. To find the total energy available to the two partons that hit each other hard -the lucky times when that happens- we multiply the two fractions and together: here is the reason why a fixed-energy proton-antiproton collision produces a variety of processes of different total released energy, , where is 1.96 TeV at the Tevatron.

Above, you can see the PDFs of the proton: the curves describe the probability to find a quark or gluon of different kinds (u,d,s,c,b, and also antiquarks , , plus gluons g) as a function of their energy fraction in the proton, x.

Now, let us make an example. In order to produce two jets with an energy each with a proton-antiproton collision, we must provide two partons such that the product of the energy fraction they carry is . That means that each of them has to carry half of the energy of the (anti-)proton which contains them; or 0.75 and 0.33, respectively!

Recall that a proton is a bag with three valence quarks plus a host of quark-antiquark pairs and gluons: one rightfully expects that the three valence quarks usually carry a bit less than a third of the proton’s energy each (because of the gluons they actually share half of the proton’s energy, on average: a sixth each). It is very rare to find energetic partons such as those of the example above! That is the reason why events with two 500-GeV jets are really rare at the Tevatron. And the PDF are what determines the relative fraction of jet events as a function of jet energy and angle.

In the sketches on the left I tried to picture a proton in two different instants of time. Besides the three valence quarks (a red, a blue, and a green one), one sees gluons and quark-antiquark pairs. Occasionally, even a high-mass quark (the red one in the bottom pic) may fluctuate out of the vacuum, vanishing quickly enough that no energy imbalance is created. 

I do not know whether I made the above explanation clear enough to retain N>0 readers to this point. If I did, I ask them one further effort: I am going to explain what else is very interesting in a collision giving rise to very high energy jets. If quarks are pointlike particles, as we currently understand them to be, the PDF are enough to describe the frequency of energetic collisions. But if quarks have a structure, then there comes a point when, by hitting them hard enough, we start to break them apart. If we ever did that, we would see that the relative frequency of those really energetic collisions would be higher than what PDFs alone predict.

In 1996 the CDF collaboration produced a very accurate measurement of the inclusive jet cross section - the same quantity now measured by D0 with seven times more statistics - which disagreed with PDF predictions at high energy: we saw more events than we thought we would, when jets had energies in excess of 400 GeV (the data points on the right in the plot below). The analysis was scrutinized with great accuracy, but no mistake was found. Were we seeing the effect of preons, the quark constituents ? 

Indeed, fits which included a compositeness scale (the energy corresponding to it) hit the data points in the head much better than fits which assumed no new physics. Here is a very good example of what Michelangelo Mangano describes in his recent paper and warns us about: the assessment of a discrepancy from known physics sources and the interpretation in terms of new physics must be two separate phases of the analysis work. And in fact, the more mundane explanation turned out to solve the mystery: the gluon PDF at very high x was not known well enough, and by modifying it just slightly the CDF discrepancy vanished! Later in 1996, D0 data confirmed that the gluon distribution was the sole offender. No preons, unfortunately…

Quarks and gluons are pointlike at the energy we probe them today. D0, with its new analysis (submitted to Physics Review Letters, preprint here), carries the horizon a bit further. But what is impressive of their analysis is observing the various cross section curves - referring to the production of jets at different angles with respect to the beam axis - all described by QCD fits with such an excellent accuracy. Please examine the plot shown below:

In the figure you see different curves - QCD predictions - and different sets of points. The cross-sections have been displaced by powers of two (x2, x4, x8, x16, x32) just to separate the sets for clarity. The sets corresponds to bins of the variable , the jet rapidity - a function of the angle to the beam. The smaller the angle, the harder it is to find jets with a given transverse energy. Transverse energy is the variable of choice for the x axis: it represents the “acceleration” that the quark or gluon originating the measured jet was provided with by the hard interaction. Remember, in fact, that the collision is not, in general, between partons of equal energy: a global motion of the center of mass of the collision is to be expected along the beam axis, but whatever flows transverse to the beam is a genuine indication of a sound kick imparted to the quark or gluon!

As I look at the great agreement of QCD curves and data points it is clear to me that no, the proton - up to energy of about a TeV - is no mystery for us today.

I recently gave a look at the statistics table of my chess games on the Internet Chess Club, and was left wondering whether I should rather spend more wisely my time. Indeed, here is the table:

In it, you can read the number of games I played, separately for each of the time controls used. The main categories are “bullet” ( one minute per player),  “blitz” (two minutes to 15 minutes, if I recall correctly), plus the fixed ”1-minute” and “5-minute” category, which include an automatic pairing system.

If you browse the numbers, you can see that I played a total of just about 10,000 games on ICC since I started with the handle “tonno” eight years ago. Ten thousand games correspond, very nearly, to about a thousand hours of play (5-minute games last on average 8 minutes, 1-minute ones on average 2).

1000 hours spent playing blitz chess! A thousand hours is a hell of a lot of time. They correspond to about seven months of work. In that amount of time I write on average two papers, sign 20 more written by others, present a talk at one international conference, and graduate a student. Am I wasting my life ?

I do not think so. Chess is a way to relax for me, and a very intellectually stimulating activity. I generate endorphines while I play. It is very nearly like a drug. And like a drug, it has anti-social connotations: my wife, in fact, hates it when I play online… But there is a sort of equilibrium which allows both of us to spend some evening time taking care of things we like.

Of course, the question remains… Maybe I could play a bit less and do other things instead. Well, yeah. Like, driving three hours to observe the night sky all night long….