During Christmas holidays I tend to indulge in online chess playing a bit too much, wasting several...

Why Measure The Top Quark Production Cross Section?

As part of my self-celebrations for XX years of blogging activities, I am reposting here (very)...

The Buried Lottery

As part of my self-celebrations for having survived 20 years of blogging (the anniversary was a...

Twenty Years Blogging

Twenty years ago today I got access for the first time to the interface that allowed me to publish...

Tommaso Dorigo

Tommaso Dorigo is an experimental particle physicist, who works for the INFN at the University of Padova, and collaborates with the CMS and the SWGO experiments. He is the president of the Read More »

The Overconstrained Standard Model

May 06 2013 | comment(s)

With the Higgs boson in the bag, the game called "global fit" that particle physicists have been playing for a couple of decades has changed significantly. The knowledge of the Higgs boson mass provided by the measurements obtained by the ATLAS and CMS experiments, added to dozens of other measurements of critical observable properties of subatomic particles that have been measured at LEP/SLC, LEPII, the Tevatron, and the LHC itself, allow us to constrain some of the fundamental parameters of the Standard Model more than direct experimental determinations do.

But what the heck is a global fit ?

The Quote Of The Week - Four-Jet Events at 130 GeV

May 03 2013 | comment(s)

"A detailed study of four-jet hadronic events at LEP 1.5 has been reported by the ALEPH collaboration. From selected four-jet events, the invariant masses of jet pairs are computed, and out of the three jet combinations, the one with the lowest difference in jet-pair masses is retained. [...] Not only is the total number of four-jet events observed by ALEPH at 130-140 GeV larger than expected from QCD, but this excess is contained in a narrow window around 105 GeV for the sum of jet-pair masses. In this window, about two times the width of the estimated resolution, nine events are observed with only 0.8 events expected from QCD."

J.Mnich, "Recent Results from LEP", SLAC XXIV Summer Institute, 1996.

Your Move

May 02 2013 | comment(s)

Last weekend I participated in a chess tournament in Mogliano. This year the event was not as strong a tournament as this used to be - only 24 players, two of them international masters. Anyway there was room for fun, since the time control was of 90 minutes for the whole game, with 30 second increments per move. This fostered a livelier play with lots of blunders especially during the second half of the games: of course the quality of the games was low with so little time to think, and younger players were favoured with respect to older ones like myself.

The Plot Of The Week - Z Plus Jets

Apr 29 2013 | comment(s)

ATLAS has just produced a very nice new study of jet production in Z-boson events. I will describe a sample graph below, but before I do I find it useful to explain to the less knowledgeable among you what a hadronic jet is, just in case you've been away during the last forty years.

Hadronic Jets: what are they ?

CP Violation In D Mesons: New Physics Or Standard Physics ?

Apr 23 2013 | comment(s)

One of the most intriguing effects in subatomic physics is the phenomenon of violation of the discrete symmetry called "CP". It is intriguing at various levels.

First of all, CP violation is intriguing because of the depth of the concept: proof of that be that it is not at all easy to explain it to outsiders (I will make an attempt below, but I am likely to fail!).

Second, its elusive nature makes it even more mysterious and difficult to study: only a few subatomic physical systems exhibit it, and the effect is visible only as a modification of measurable quantities at the level of a few parts in a thousand.

The Quote Of The Week - G.H.Hardy, Second-Rate Minds

Apr 18 2013 | comment(s)

"It is a melancholy experience for a professional mathematician to find himself writing about mathematics. The function of a mathematician is to do something, to prove new theorems, to add to mathematics, and not to talk about what he or other mathematicians have done. Statesmen despise publicists, painters despise art-critics, and physiologists, physicists, or mathematicians have usually similar feelings: there is no scorn more profound, or on the whole more justifiable, than that of the men who make for the men who explain.