Bigger is better

Since its discovery in 1995, our understanding of the top quark has improved, mostly due to improvements in accelerator and detector technology. Today's article describes an early analysis using the LHC data taken in 2015. The fact that it is about top quark production is a testament to changes in technology, as well as superb effort by the scientists involved.

Since its discovery in 1995, our understanding of the top quark has improved, mostly due to improvements in accelerator and detector technology. Today’s article describes an early analysis using the LHC data taken in 2015. The fact that it is about top quark production is a testament to changes in technology, as well as superb effort by the scientists involved.

I’d like to start by stating the obvious. Analyzing frontier physics data is hard. When you record data using a cutting-edge particle accelerator like the LHC or the Tevatron in its heyday, you encounter lots of ways of getting things wrong. It can take years for scientists to understand the little imperfections of their detector and figure out how to correct for them.

The LHC just resumed operations in June, this time at a collision energy of 13 trillion electronvolts, which is a little over 60 percent higher than when it last ran in 2012. Given that scientists have been looking at the data for under half a year, the first physics analyses are of the simplest topics — ones for which a subtle understanding of the detector’s performance is not needed. Thus it is (in my not very humble opinion) a breathtaking achievement that one of the first papers submitted for publication using data recorded in 2015 was the production rate of top quarks.

Some of you will remember the excitement in 1995 when the top quark was discovered here at Fermilab. After painstaking effort, DZero and CDF scientists teased out a tiny signal from an overwhelming background. It was a very hard thing to do. So what changed?

We are told that bigger is better, whether it be for football players, paychecks or slices of Mom’s apple pie. But that aphorism really does apply when it comes to particle accelerators. The LHC is colliding beams at an energy that is 6.5 times higher than was possible at the Tevatron and at a much higher rate of collisions per second. Both of these contribute to a much improved ability to produce top quarks. In fact, the rate at which top quarks are produced at the LHC is about 100 times that of the Tevatron for the same amount of delivered beam. What was once hard is now easy.

Mirena Paneva of the University of California, Riverside, made important contributions to this analysis.

Mirena Paneva of the University of California, Riverside, made important contributions to this analysis.

This CMS analysis is a simply brilliant accomplishment that exploited the enhanced capabilities of both the accelerator and the detector. The result is that the increased production rate is in exact accordance with the predictions of the Standard Model.

This is both good and bad. It is good because it again affirms just how good the theory is, and it is bad because it says that there are not yet any surprises in the production of even the heaviest particle ever discovered. This suggests that the road to a paradigm-changing discovery might be steeper than we hoped. But the universe is not obliged to make things easy for us, and it is our job to accept its secrets, whatever they may be.

See other science results from Fermilab.