Quantum Diaries

The massive size of the DZero detector is evident in comparison to the size of the man standing near the top of the image. Credit: Fermilab

What’s the winter conference season? We pretty much take data all the time, and we analyze the data and produce dozens of results every year. These analyses are ongoing, but there are two big events in the year where experiments here and at the Large Hadron Collider at CERN aim to roll out new results. That’s the winter and summer conferences. It’s kind of like when the fashion designers send their latest creations down the runway, hoping to turn as many heads as possible. These conferences are where we introduce to the world our latest and greatest insights about the nature of the universe.

The biggest winter conference is “Rencontres de Moriond” held in the Italian Alps, and it just completed two weeks ago. The big summer conference changes from year to year, and last year it was the International Conference on High Energy Physics, or ICHEP, in Paris. I was fortunate to give a talk for DZero at that one (yes, a perk of being a physicist is that every now and then you get to go somewhere nice).

 A deluge of data:

As a scientist on DZero and head of the team that runs the data handling for many Fermilab experiments, things get busy in many ways when we gear up for the conference seasons. For example, physicists run computer programs to analyze the mountain of data that comes from the detector. The computers are always busy, but before the conferences they get super busy as people try to finish up their analyses. For those weeks we deliver around 200 terabytes of data per day! The amount of data in 200 terabytes is equivalent to watching a high-definition television station non-stop for 2 ½ years (that reminds me that my 5-year-old daughter needs to watch less TV)!! Our data-handling system is very robust and tends to run itself. But, this season the demand for data was so great that some future plans to make it more efficient had to get implemented very quickly. Fortunately, that all worked and now it’s ready for even greater demands that may be coming in the summer.

 The Results:

A smattering of results from DZero for the 2011 winter conferences. Click on image to make it larger. Credit: DZero

I’m also a “subgroup” convener, which means I organize a small group of analyses and the people doing them. Probably the most exciting result being presented this winter is the Tevatron mass exclusion for the Higgs boson, which was written about previously in Quantum Diaries. But there are lots of other new results as well, including two from my subgroup.

One result is an updated result, which means we’ve analyzed more data, from an analysis that looks for collisions that produce two Z bosons (ZZ). These events are very, very, very rare. In fact in the Standard Model, the theory that describes sub-atomic particles, the Higgs is the next rarer process. Showing that we can find ZZ proves that we really understand our detector and our data. And, in fact, the result shows that we find ZZ at the level the Standard Model predicts.

The other analysis looks for events that have a W boson and a photon (the latter is a particle of light). We now see a few hundred of these events and have a clear picture of the “radiation amplitude zero”, which is an interesting effect predicted by the Standard Model that says that the W and photon fly off in some directions more often than others.

I mentioned I was lucky enough to give a talk at last year’s big summer conference. It was exciting to be in Paris, which is my favorite foreign city and where I’m reminded how much of my high school French I’ve forgotten. But it was also exciting because that was the conference where the new LHC experiments showed their first results.

 This winter they had more results and joined us in comparing experiment with theory. While the LHC is just starting, as you may have heard, the Tevatron will wind down soon. But that doesn’t mean we’re done. We will have lots more data and lots more analyses, including possibly some new ones. The results from our final data set will be appearing at many summer and winter conferences to come!

— Adam Lyon