Measuring Oscillations of Strange Bottom Mesons Is Hard Work

I read the preprint of CDF’s on the observation of Bs mesons. It took a remarkable amount of work. Large high energy physics collaborations have large author lists due to the large contributions made by many people to operate and calibrate the detector, simulate and process the data. But the analysis described in most papers is done by a very small group of people, usually a graduate student and his or her adviser or a postdoc.

This analysis requires the observation of Bs mesons and a measurement of their momentum and decay point. In addition it is necessary to determine whether it was produced as a Bs meson or the antiparticle. In order to get a large enough sample to be statistically significant, CDF had to use many decay modes of the Bs and some of these were only partially reconstructed, which means that one particle escaped detection which hurts the momentum resolution and can increase the background. CDF also had to use multiple techniques, called tags, to identify whether the original Bs was a particle or antiparticle.

A graduate student could be expected to do an analysis that used one tag and a small number of similar decay modes. Clearly this work had to split up among a number of people. Some of the partially reconstructed modes using leptons would require very detailed studies to understand the effect on the momentum resolution. Combining the results in the end is also a big job. Making sure that the various data samples were independent or that any correlations were understood is critical.

This is a very impressive result. Having studied B mesons for many years, I can appreciate the amount of work that must have gone into this analysis.


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