Physics

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.

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 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.

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.
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.
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.
In the most recent edition of PhysicsWorld, there are two articles that on the face of it have little to do with each other: one is about Jan Hendrik Schön, the physicist formerly famous for creating the first organic superconductor and the first single-molecule transistor, and now most famous for having simply made up all of those results out of thin air, the greatest kind of scientific fraud in physics.

The other article is about how the internet is transforming scientific communications, looking at which new means of scientific communication failed (such as Physics Comments and scientists contributing to Wikipedia -- although Scholarpedia is taking off quickly at the moment, probably because its signed and peer-reviewed authorship model is more in line with academic customs than Wikipedia's semi-anarchistic one) and which succeeded (the arXiv) in making the dissemination of scientific results quicker and more transparent.

At first glance these two topics appear to have little to do with each other. At second glance, however, they are closely intertwined.
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.
Researchers in condensed matter physics at the University of Pennsylvania and the University of Chicago have created an experimental and computer model to study how jamming, the physical process in which collections of particles are crammed together to behave as solids, might affect the behavior of systems in which thermal motion is important, such as molecules in a glass.

The study presents the first experimental evidence of a vestige of the zero temperature jamming transition — the density at which large, loose objects such as gas bubbles in liquid, grains of sand or cars become rigid solids such as foam, sand dunes or traffic jams — in a system of small particles where thermal energy is important.