Hot news in ’22, but this was based on data collected by 2011!
https://www.nature.com/articles/d41586-022-01014-5
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Old experiment, new tricks
In the latest work, Kotwal and his collaborators aimed to take the most precise measurement ever of the W’s mass. The data had all been collected by 2011, when Fermilab’s Tevatron — a 6-kilometre-long circular machine that collided protons with antiprotons and was once the world’s most powerful accelerator — shut down. But the latest measurement would not have been possible back then, says Kotwal. Instead, it is the result of a steady improvement of techniques in data analysis, as well as the particle-physics community’s improved understanding of how protons and antiprotons behave in collisions. “Many of the techniques to achieve that kind of precision we had not even learned about by 2012.”
The team looked at roughly four million W bosons produced inside the CDF detector between 2002 and 2011 — a data set four times larger than the group used in an early measurement in 20122. The researchers calculated the energy of each decay electron by measuring how its trajectory bent in a magnetic field. One painstaking advance over the past decade improved the resolution of the trajectories from roughly 150 micrometres to less than 30 micrometres, says Kotwal.
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