A Quantum Diaries Survivor

This is going to be a rather long piece, so for the lazy and the absent-minded among you I decided to put together an executive summary at the top, and not at the bottom of the article as I usually do. It is a bit of a spoiler, but those of you who can invest some time reading about particle physics will not be deterred by the first few lines of text. Besides, an executive summary is needed because we are discussing real news here: so here it is.

This afternoon Lisa Randall, one of the most famous theoretical physicists of our time, received from the hands of Flavio Zanonato, mayor of Padova, the keys of the city.

A new paper in the Arxiv attracted my attention this morning. It is titled "Perturbative QCD effects and the search for a signal at the Tevatron", and is authored by a set of quite distinguished theorists: C.Anastasiou, G.Dissertori, M.Grazzini, F.Stockli, and B.Webber.

Last Tuesday CDF announced their own discovery of the Omega_b baryon, a measurement which creates a controversy with the competing experiment at the Tevatron collider, DZERO. That is because DZERO had already claimed discovery for that particle, almost one year ago, and because the two measurements disagree wildly with each other. Just browse through my past few posts in this column and you will find all the information you need (how lazy can one be with links?).

In the last few days I indulged in a rather technical description of the checks I made on DZERO's evaluation of the significance of their observation of Omega_b particles. In those occasions I did not discuss either what the Omega_b is, nor what is its relevance, nor the details of how DZERO collected a small but significant sample of events characterized by the production of that ephemeral particle.

In a previous article here I considered from a statistical standpoint the signal of Omega_b candidate decays extracted by the DZERO collaboration in a large dataset of proton-antiproton collisions -the ones produced by today's most powerful hadron collider, the Tevatron at the Fermi National Accelerator Laboratory.

A first observation of the Omega_b baryon -a quite exotic particle composed of a bottom quark and two strange quarks- has been recently published by the DZERO collaboration. Their paper claims to observe the so-far-unseen particle in 1.3 inverse femtobarns of Run II data (about a hundred trillion proton-antiproton collisions, that is).The claim is based on the signal they find, 17.8 fitted events making a peak in the reconstructed mass distribution, a signal whose significance is computed to exceed five standard deviations: 5.4 of them, to be precise.

With an unexpected move, the Austrian Minister of Research and Science, Johannes Hahn, announced last Friday that he intends to put an end to the 50-year-long participation of Austria to CERN.Such a move is hard to understand, in light of the great prospects of physics that the start-up of LHC will bring at the end of this year. Losing membership to CERN would mean a downgrade of Austrian scientists in all the projects they are involved, and it would be detrimental to the experiments, to the lab, and to particle physics in general, but most of all it would be a catastrophe for Austrian research.

The Fermi collaboration released yesterday a paper describing their measurement of the electron and positron flux of cosmic rays. Simultaneously, a second paper was published by the HESS collaboration on the very same topic. Together, these two important new articles provide the means for a significant advancement in our understanding of the spectrum of electrons and positrons from nearby sources.It is especially meaningful to consider the two results together because the two instruments are as different as salt grains and tequila. Let me see where to start:

Triggered by a preprint appeared three days ago on the ArXiV -a fundamental resource for particle physicists willing to stay in touch with the latest developments of the theory and new experimental results-  this morning I was gearing up to write a post with a careful, didactical discussion of why we believe that the subnuclear world includes three generations of quarks and three generations of leptons, what is the evidence for this peculiar fact, and what would a fourth generation of matter imply for e.g. searches of the Higgs boson. Unfortunately, my memory is still good enough to let me remember that I did write about those things in my old blog, about one year ago.

These are hard times for evil guys like me, who are always willing to speculate wildly on particle physics results -only to secretly chuckle at the ripples their extrapolations make, knowing for a fact that the Standard Model is as solid as it has ever been.Suggestive new results which offer themselves as the first hint of a breakdown of the Standard Model are indeed quite rare nowadays. In a famous post which originated a $1000 bet (taken up in part by Prof. Gordon Watts and in part by Prof. Jacques Distler), no less than 32 months ago I was writing in my old blog:

Here is the concluding part (for the first part see here) of a discussion of a few subtleties involved in the extraction of small new particle signals hiding within large backgrounds. This is a quite common problem arising in data analysis at particle physics experiments, but it is not restricted to that field. Quite on the contrary: narrow Gaussian signals are commonplace in many experimental sciences, and their identification and measurement is thus an issue of common interest.