A Quantum Diaries Survivor

New important information on high-energy particle physics has recently been released by the CDF experiment, one of the two detectors scrutinizing the 2-TeV proton-antiproton collisions copiously produced by the Fermilab Tevatron collider located near Batavia, Illinois (see aerial view of the site below). The CDF experiment has ruled out the existence of so-called "Z' bosons" (particles extraneous to the Standard Model which are predicted by a number of new physics models) for Z' masses below one Tera-electronvolt.

Betting a grand on the existence or not of new physics is cool, but one does not need to be that daring (or to be that daring every other day) to enjoy the game of making predictions for what the fundamental research in experimental particle physics will discover or measure in a future close enough that we can reasonably expect to experience ourselves. So here I am, at the end of this eventful 2010, to look forward rather than backward, with no additional grand to invest but some insight to use, some reputation to waste, and a bit of humour to stuff between the lines.

A reader of this blog asked in the comments thread of a recent piece the following interesting question:"Assuming mH = 201 GeV/c2, how many Higgses shoud have been produced atthe Tevatron by now with an integated luminosity of 10 inversefemtobarns? And how many H -> ZZ -> µµµµ would one expect to see?"

As sure as death and taxes, and as timely as a Swiss watch, the Tevatron collider never ceases to awe us. Well into its twentysixth year of life, the aged and celebrated proton-antiproton collider sitting just a few meters underground in the west Chicago suburbs hit the mark of 10 inverse femtobarns of collisions delivered to the core of the CDF and DZERO detectors.10 inverse femtobarns! Ten inverse femtobarns of proton-antiproton collisions is a HELL of a lot of them. Plus, you should multiply that number by two, since the same number of collisions happened inside two different collision areas -those manned by the two competing collaborations.

A new result for the production cross section of Z boson pairs in proton-antiproton collisions at the 2-TeV Tevatron collider is now public, thanks to the efforts of the CDF collaboration. The measurement, in a nutshell, confirms Standard Model predictions nicely: the cross section is determined to be 1.45 picobarns, with an asymmetric error bar of of +0.60-0.51. The Standard Model, on the other hand, predicts that the cross section is 1.21 picobarns. The agreement of the two numbers, within uncertainties, says that all is well in the searched final state, and no unforeseen effects are at work.

Our present understanding of fundamental physics implies the existence of three generation of matter particles, which we consider structureless and "elementary", both in the sense that they cannot be divided into smaller entities, and in the sense that they are the building blocks of all observed manifestations of matter.

The time is now. If you are going to fantasize about the possibilities of an extended Tevatron running and how likely it is that your favourite physics model may be tested by CDF and DZERO, you are advised to get in the game.

A really interesting piece of news comes from the CERN laboratory today. The CMS experiment has detected a handful of Z boson decays in events featuring the collision between heavy ions, accelerated to energies of hundreds of GeV per nucleon.

Scientific American features an excellent article by Garrett Lisi and James Owen Weatherell, with title "A Geometric Theory of Everything". It is a rather clear explanation of the ideas behind the recent articles published by Lisi on the E8 group and how this exceptionally rich mathematical structure could embed the representation of all particles and forces of nature.

As beautiful as they get, or even more so. It is hard to express the beauty of the event that the CMS collaboration published today. CMS, which stands for "compact muon solenoid", is one of the two main detectors operating at the CERN Large Hadron Collider (the other is ATLAS). The duo is seeking evidence for the Higgs boson, the only elementary particle predicted by the Standard Model that still awaits to be discovered.

Giorgio Chiarelli is a particle physicist. His research activity has been based largely at the Fermi laboratory near Chicago, US, at the CDF experiment. In 1994-96 he actively participated in the discovery of the top quark and in the first measurements of that particle's properties. Later, after directing the construction of a part of the new CDF detector, he moved its research interests toward the search for the Higgs boson. Currently he is a INFN research director in Pisa, where he leads the CDF-Pisa group. In the most recent years he dealt with problems connected with the communication of science.

The ATLAS collaboration has just released an important study of the sensitivity to a standard model Higgs boson. For the first time precise predictions are made for LHC running at a centre-of-mass energy of 7 TeV (but also 8 and 9 TeV are considered, given the possibility that next year the energy is bumped up a bit), and for most of the sensitive channels together.The public document is long and detailed, and I have no time to discuss its intricacies with you here, nor do I believe that you would actually want me to. But I do want to discuss one of the most significant figures in the note. It is shown below.