Physics

The "new" section of experimental physics papers in the arxiv today features a preprint by the CDF collaboration, titled "First Observation of Vector Boson Pairs in a Hadronic Final State at the Tevatron Collider". This is another instance of a difficult analysis where the CDF and DZERO experiments have competed in the past, and one which is relevant for Higgs boson searches. And CDF got there first once again. I will describe in detail the analysis and the results later today, because this particular study is dear to me for at least three different reasons: I have always worked at the…

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. The ceremony is part of this years' celebrations for the Anno Galileiano, and the World Year of Astronomy. Padova is the place where Galileo Galilei, the father of the scientific method, taught for 18 of his best years. To commemorate Galileo and popularize science, the city of Padova has set up an excellent exhibition dedicated to his work and the scientific method. Also, the city has started giving the title of honorary…

This morning the Planck 09 conference started at the Auditorium Altinate (see picture, right) in Padova. For a week, theorists and experimentalists will discuss hot topics in a variety of fields, from particle physics to cosmology, to string theory. A PDF file with the program is online. I am attending the conference and will be taking notes on some of the talks. Of course the slides of all presentations are going to be online very soon, but even for experts I find that a summary is beneficial. It is tedious to open all pdf or ppt files in search of something remarkable -much better to rely…

When Albert Einstein constructed his general theory of relativity he decided to resort to some reverse engineering and introduced a 'pressure' term in his equations. The value of this pressure was chosen such that it kept the general relativistic description of the universe stable against the gravitational attraction of the matter filling the universe. Einstein never really liked this fudge factor, but it was the only way to get the equations of general relativity to describe a universe that is static in size. More than 10 years later, Edwin Hubble's observations showed that the universe is…

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. The paper is quite technical and a detailed discussion of its content does not belong here. However, given the importance of its results, I wish to provide with a short summary those among you too lazy to download the paper. The authors consider the effect of Next-to-Next-to-Leading order (NNLO) corrections to the process of…

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?). I already discussed why the comparison of the two measurements shows that the one we have to abandon is DZERO's. Here, I will just…

In thirty minutes (4 PM Chicago time) a live streaming of the Omega_b discovery by CDF will be broadcast at this link: http://vms-db-srv.fnal.gov/fmi/xsl/VMS_Site_2/000Return/video/r_live.xsl Please follow it if you are interested in particle physics - Pat Lukens, the main author of the analysis, and a very experienced and skilled physicist who has spent the better part of his life for the good of the CDF experiment, will be discussing this fantastic new analysis for all of us. If you want more details on this measurement, and some background information accessible to non-scientists, please…

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. I wish to fill that gap today, and I hope I will be able to keep the discussion at a level which enables anybody who is interested in particle physics to follow it. In so doing, I will probably…

Good news today. Yesterday afternoon Werner Faymann, the Austrian Federal Chancellor, announced that Austria will not leave CERN, as previously suggested. An official confirmation of this decision will be received this afternoon by letter by the President of the CERN Council. The decision of Austria does not surprise me - it would have been both crazy and self-destructive for Austrians to decide to leave the rich program of particle physics that they have contributed heavily to make a reality. The LHC, most notably, will start producing knowledge of a totally new energy frontier next year,…

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. The signal of that fancy baryon, according to the DZERO collaboration, exceeds the significance of "five standard deviations", the coveted goal above which a new particle is certified to have been unequivocally observed. A signal is said to have a significance of 5-sigma when the…