Luminosity Profile June 19, 2007Posted by gordonwatts in physics.
Yesterday, Dmitri, one of our co-spokes person, showed this plot. I like this plot because it really made me rethink what is going on with our experiments luminosity. I like plots that jar me out of some preconceived notion I have.
Our experiment lives and dies by the amount of data it gets. Until recently the Tevatron accelerator was breaking high luminosity records. These high luminosities are tough to handle for the experiments: so much data arrives in such a short time that we often have to throw some of it on the floor just to keep up! Not good. We tend to focus most of our conversation on these issues.
The plot, however, shows that the bulk of the data we collect is otherwise. That plot is the luminosity profile for Run IIb. IIb is since we installed our inner layer of silicon — last summer. The x axis of that plot is the luminosity. The bulk of the events we have recorded were taking close to 50E30 — a fairly low luminosity (we get stressed out at about 200 or above). So it isn’t incorrect that our systems are still optimized for those lower luminosities: that is where we get most of our data!
That being said, however, there is a general rule of thumb in particle physics. New and interesting results and physics only occurs when you double your data. Most results coming out of the experiment are about 1 fb-1 of data. The next round of results will be between 2 and 3. After that we will need more than 4 to make real progress. In order to do that in a timely fashion (i.e. before the LHC starts up), the Tevatron will have to deliver more and more luminosity. One main way to do that is move the average of that plot to the right! And then we will need to re-optimize our system to deal with the higher luminosities!
This plot was done by Boris Tuchming for some of his muon studies. If you want to see it in context, check out D0’s talk at the P5 meeting.
Update: See comments for more details of the makeup of this sample.