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Where are the 4 fb-1 Results!? May 2, 2008

Posted by gordonwatts in Uncategorized.

Congratulations to everyone at D0 and the Fermilab accelerator division — D0 has been sent 4 fb-1 as of April 30!! That is a lot of data! And years of work!

It will be a while before you see that in an analysis however. First of all, of the 4 fb-1, only about 3.5 fb-1 were written to tape. The rest is lost forever. Where did it go? Well, perhaps our detector was broken for some short amount of time. We do our best to make sure that doesn’t happen of course, but a machine like this does break (my name is no more than a few of those minutes for Level 3/DAQ problems!) We generally run our triggers with a small fraction of dead-time — time where we aren’t accepting new events even if they are coming in – if we were to run with zero dead-time we’d not be able to do nearly the physics program we do [if you want more details, let me know].

The second issue is time. It takes time to understand our data – a while to do something as sophisticated as a Higgs search. Parts of the detector are turned off, which affect efficiencies and systematic errors. The events we trigger on are changed as we try to optimize our data for the higher instantaneous luminosity the Tevatron delivers. On top of that, of course, is the continuous effort to improve our analysis technique’s power. All these changes must be carefully studied to see how they impact each analysis. And once that is done, only then can the data be shown externally. This takes quite some time. The more sensitive the analysis, the more carefully the data must be studied.

So, fantastic for us at D0 (and CDF) for reaching 4 fb-1 delivered. Thanks to the Fermilab accelerator division for doing this despite the trying times. Everyone else: sorry, you’ll have to hold your horses a short while before we show the results of this data!


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