I once was an active chessplayer, but work duties have long taken tournaments off my plate - I simply do not have the time to sit through long hours of chess battles. So I play blitz online on chess.com (my handle is "tommasodorigo", in case you wondered).
On Friday evening I was in Tesero, where a crowd of 150 interested laypersons attended my talk on particle physics, organized by the very active Gruppo Astrofili Fiemme. There, among other things, I discussed the challenge that is on between the Fermilab experiments in the United States and the CERN experiments in Europe. I will discuss elsewhere the successful evening; here I just want to show the status of data collection by the two challengers.
Being still in the middle of a rather long vacation (now in the Italian eastern alps), my blogging power is limited. So today I will just offer you some thoughts on the recent measurements of a fundamental parameter of the Standard Model called "W boson width". The W boson, like any unstable subatomic particle, has a very short lifetime, which depends on the strength of its couplings to lighter particles, on its own mass (generally the heavier a particle is, the faster is its disintegration), and on the availability of lighter bodies into which to decay without breaking any fundamental rule.
W bosons have been thoroughly studied at the Tevatron collider. Discovered by the UA1 experiment at the CERN SppS proton-antiproton collider in 1984, these particles have since been produced also in electron-positron collisions at LEP II (in pairs), and recently at the Large Hadron Collider. But the CDF and DZERO experiments have some of the most precise measurements of the physics of these particles, thanks to their now very large datasets.
This is a good year for summer meteor watching. The moon, just past new, will not interfere with observations of faint meteors. And the Perseid shower, originated from the dust left behind in the orbit of comet Swift-Tuttle, will produce a nice show. Perseids are a rather stable stream, and they produce a detectable rate of meteors from late July to late August, with peaks in the nights of August 11th and 12th, depending on the exact trajectory that the Earth takes while plunging in the dust-ridden area of the solar system. The rate is usually encoded in the acronym "ZHR", for zenith-hourly-rate. ZHR values of 100 to 150 are common for the two highest-rate nights.But what exactly should you expect to see ?
CDF and DZERO, the two experiments at the Fermillab Tevatron collider, have studied top quark production since their own discovery of the heavy particle in 1995 (see here, here, and here for a three-post history of the top quark quest).
What picture should we draw of the quest for new phenomena after the presentation of a wealth of new results at the international conference on high-energy physics in Paris held last week ? I am speaking in particular of results coming from the experiments at the Tevatron and LHC, which are all studying hadron collisions in search for still unseen effects to both confirm (with the discovery of the Higgs boson) or break down (with the observation of Supersymmetry, new particles, extra dimensions, or still other effects) the present theoretical understanding of fundamental physics which the standard model provides us with.
After the issuing of new top mass results by the Tevatron experiments, it is time for another look at global electroweak fits of standard model observables. The Gfitter group has produced new fits for the standard model in search of the most probable value of the Higgs boson mass, given the new measurements of top quark mass and other quantities, and the huge amount of existing information on sensitive observables from the standard model. Unfortunately, I could find no update including the new Higgs search results yet. I guess such a fit will be ready in a few weeks... But the new released information is already interesting enough that we may meaningfully spend a few words around some figures here.
While the focus of the international conference in high-energy physics in Paris last week has been on the search for new physics and the precise measurement of standard model quantities, I will offer to you today something more technical, but in no way less physics-rich; it was presented in Paris, but with the many parallel sessions it may have well gone unnoticed... What I wish to explain to you is the procedure by means of which the CMS experiments calibrates the scale and resolution of its charged particle momentum measurement.
While everybody is busy discussing the latest Tevatron results on the Higgs boson searches -is that the light-mass excess the internet was abuzz, is it consistent with a signal as we expected it, how long will it take to confirm it is not a fluke, etcetera, etcetera, etcetera- I think I have a different plot with which to enthuse you. If you do not like the figure below, courtesy CMS Collaboration 2010, you are kindly requested to leave this blog and spend your time reading something else than fundamental physics. I do not know what will ever make you believe particle physics is beautiful, if not what is shown here.
The parallel sessions at the international conference on High-Energy Physics in Paris are over, and it is time for a summary of results. Of course if you are following the conference you will get it from the summary talks, but if you prefer some armchair, remote attendance of the conference, I have collected for you a few meaningful plots. Here I wish to assemble some of the electroweak physics results produced by CMS in time for ICHEP. The CMS experiment has shown results that use up to 280 inverse nanobarns of proton-proton collisions, but for electroweak measurements -those involving W and Z signals, to be clear- the statistics used is up to 200 inverse nanobarns of well-understood data.
Ashay Dharwadkeris the founder and director of the Institute of Mathematics, Gurgaon, India. He is interested in fundamental research in mathematics, particularly in algebra, topology, graph theory and their applications to computer science and high energy physics. Based upon the new proof of the four color theorem, he has developed a grand unified theory for the Standard Model and gravitation. In particular, this leads to a mathematically precise prediction of the Higgs boson mass.
The CMS collaboration at the LHC collider has just produced its very first results on the production of Upsilon particles, with 280 inverse nanobarns of proton-proton collisions at 7 TeV center-of-mass energy. I wish to discuss these results here, to explain what is interesting in these very early measurements, and what we can expect to learn in the future from them.The production of resonances decaying to muon pairs is one of the first things one wants to study when a hadron collider starts operation. This is because these particles are extremely well known, so one immediately figures out whether the detector is working properly, what is the resolution on the momenta of the reconstructed particles, etcetera.
