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LHCb Measures Unity, Finds 0.6

With a slightly anti-climatic timing if we consider the just ended orgy of new results presented...

Waiting For Jupiter

This evening I am blogging from a residence in Sesto val Pusteria, a beautiful mountain village...

Winter 2017 LHC Results: The Higgs Is Still There, But...

Snow is melting in the Alps, and particle physicists, who have flocked to La Thuile for exciting...

The Way I See It

Where by "It" I really mean the Future of mankind. The human race is facing huge new challenges...

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Tommaso DorigoRSS Feed of this column.

Tommaso Dorigo is an experimental particle physicist, who works for the INFN at the University of Padova, and collaborates with the CMS experiment at the CERN LHC. He coordinates the European network... Read More »

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A few months ago LHC took a special run of proton-proton collisions at  2.76 TeV. Why the lower energy, now that we are accustomed to searching for new phenomena at the highest available energy of 7 TeV ? Because of the wish to compare lead-lead collisions, taken last year at 2.76 TeV nucleon-nucleon energy, with proton-proton ones. The comparison allows to extract extremely interesting results.
Just a short post to mention that the Large Hadron Collider has reached tonight the top instantaneous luminosity of 1.075 * 10^33 cm^-2 s^-1. This is a new record for high-energy hadron colliders, improving over precedent records already set this year by the CERN machine. The peak luminosity is 2.5 times larger than the highest reached at the Tevatron (which, one needs to remember, collides protons against antiprotons, and the difficulty in producing the latter makes the comparison between LHC and Tevatron luminosity a bit deceiving).
The plot of the week is actually a table this week. A histogram with several background components can be extremely informative, but sometimes a table provides more detail and one can focus better on interesting features.

The table below has been produced in a CDF search for events containing same-sign lepton pairs: a striking signature of new physics, faked by very few processes. Because of the paucity of Standard Model sources, even relatively small new physics signals can emerge in such a sample. The CDF analysis is based on 6.1 inverse femtobarns of proton-antiproton collisions collected at the Tevatron during Run II. Let us see what the table tells us.


Last night I had the pleasure to visit Mauro, a friend of mine and an amateur astronomer. Mauro owns a 24" dobson telescope with a mirror crafted by the superb hands of Romano Zen, the same who made my own 16". The precision of the optics of Romano is legendary, and as far as my limited capabilities allow me to judge, his reputation is entirely deserved. With my dobson scope I have been able, in nights of lucky seeing, to discern details on Jupiter of the order of half an arcsecond in angular extension. And with Mauro's 24"...
A question posed by Tony Smith in the thread of the previous post (which dealt with the choice of the bin width in histograms) triggered me to do a little work to produce a convincing answer to him.

The issue is the following. Tony got interested in a few top candidate events in a few mass distributions published by CDF and DZERO quite some time ago, which seemed to all cluster in the surroundings of 145 GeV. Could those eight candidate events (once summed across the various channels and experiments) be the signal of some resonance different from top quarks ?
I was unaware of the following story, which was brought to my attention by Monica Pepe-Altarelli yesterday. Since I totally agree that nobody should be detained without proof of guilt for long periods of time, and since we are talking of a physicist, I am glad to broadcast the story here.