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Holiday Chess Riddle

During Christmas holidays I tend to indulge in online chess playing a bit too much, wasting several...

Why Measure The Top Quark Production Cross Section?

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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 and the SWGO experiments. He is the president of the Read More »

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How could I miss it - and you did too. A very comprehensive article on standardization as a way to reduce environmental pollution has appeared here, and has almost gone unnoticed. I think it is worth reading, if only to acknowledge the existence of this issue and the need for all of us to pay attention to it.

Here is an excerpt of Enrico's conclusions from the study:
A paper describing the first evidence of top pair production in association with a energetic photon has just appeared on the Cornell Arxiv. This search has been performed by the CDF collaboration in a sample of 6 inverse femtobarns of proton-antiproton collisions.

There is nothing strange or particular about the fact that any hard production process at a hadron collider can produce, in addition with a massive state such as a top pair, additional energetic photons. That is because any charged particle involved in the process will have a small but finite chance of radiating electromagnetic energy, with a strength governed by our good-old fine-structure constant.
The ATLAS Collaboration, one of the two high-energy physics experiments at the CERN Large Hadron Collider, has just produced updated results of their ongoing search for new heavy particles decaying into lepton pairs. They are now using up to 236 inverse picobarns of 7 TeV collisions, which is seven times more data than previous searches based on 2010 datasets. A seven-fold increase in data size grants a significant increase in sensitivity, so it is worth taking a look at what they see.
New results from the T2K collaboration have been presented at a KEK Physics Seminar today, and they are really interesting stuff. In a nutshell, six electron neutrino events have been seen by their far detector, illuminated by a pure and intense beam of muon neutrinos. The estimated backgrounds from non-oscillating-neutrino sources are estimated to amount to 1.5+-0.3 events, and the observed counts thus constitute a 2.5-standard-deviation effect, hopefully a first hint of direct detection of nu_mu -> nu_e oscillations.
The LHC has been running very well in the last few weeks, and I can announce, with some anticipation, that the 1-inverse-femtobarn line will be crossed in the next few days. Check it out in the figure below, which shows, together with the delivered luminosity (red line), the one acquired by the CMS experiment (that is, the part acquired with CMS fully operational).

The total bounty available before the next shutdown (end of June) is probably going to amount to 1.3-1.4/fb. Expect exciting new results by ATLAS and CMS for the summer 2011 conferences!
CMS has recently produced an updated search for black hole production in the 7 TeV proton-proton collisions delivered by the LHC. The data sample now consists of 190 inverse picobarns of collisions collected in 2011, and the limits set on black hole production are more stringent.