A Quantum Diaries Survivor

I devote only a short piece today to the topic of the week -or the month- in particle physics: as many of you already know, yesterday the CMS collaboration has made public the results of their analysis of two-particle correlations, which evidences an effect never seen before in hadronic collisions, and which has been saluted very emphatically by the press around the world.The Analysis In Ten Lines

A very important new theoretical study has appeared last Tuesday in the hep-ph preprint arxiv. Titled "Precise Predictions on W+4 Jet Production at the Large Hadron Collider", it is signed by a strong team of theorists: C. Berger, Z. Bern, L. Dixon, F. Febres Cordero, D. Forde, T. Gleisberg, H. Ita, D. Kosower, and D. Maitre.I believe it may be quite useful if I review here the paper results, and explain to you why they are very important for the physics of the LHC. But first, I feel that there are a few details concerning the process of W+jets production at the LHC which might be obscure to most of you. Let me straighten them out -it is worthwhile to do it!Preliminaries

No, it is not a typo. I do mean "quirks": these are hidden-valley brothers of quarks predicted to exist in some fancy new physics scenarios. These particles have been sought by the DZERO experiment in a large dataset of proton-antiproton collisions, making use of a neat technique which I thought could be interesting to briefly explain today.

Back to breathing the air of Fermilab after a full year away, I got to gauge a bit better the aftermath of the little incident created by a posting of mine in July. As often happens with internet bubbles, they look quite dramatic as they inflate, but they leave no big scars. Two months have passed, and this looks like a good time to post here some ruminations about the general issue.Physics Experiments And Confidentiality

A new paper produced by the DZERO collaboration got me quite interested today, for several reasons. The analysis is based on a large data sample: over seven inverse femtobarns of proton-antiproton collisions! This is a huge dataset, the result of about 500 trillion proton-antiproton collisions! In fact, the measurement these data has made possible is extremely precise and it exposes quite strikingly the shortcomings of our present modeling of the production of vector bosons.

The Standard Model of particle physics has been under attack since its original formulation, in 1967, and yet it has so far resisted every assault; in so doing it has become one of the most thoroughly tested physical theories. Like it or not, the construction has stood the test of time so well that theorists and experimentalists alike feel threatened by the chance that the Large Hadron Collider, too, will fail to find new physics beyond what the model predicts.

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.