The power of two top detectors

Complementary experiments enhance the Tevatron physics program by improving searches and measurements.

Two independent experiments, CDF and DZero, recorded the results of the proton-antiproton collisions provided by the Tevatron, and their complementary efforts have proven greater than the sum of their parts. Each collaboration scrutinizes its collected data, searching for signs of new physics while making precise measurements of particle properties in order to improve our understanding of the Standard Model. Comparing and combining the separate results from each collaboration can benefit the field of high-energy physics more than if a single experiment had just collected twice as much data.

The detector is the “lens” a particle physicist uses to investigate the subatomic world. The CDF and DZero detectors are like two different digital cameras, each as large as a four-story apartment building. A significant amount of effort in each collaboration goes into understanding how its particular detector will affect the way scientists see subatomic interactions, and these effects must be carefully accounted for in each physics analysis. Each group of physicists may also perform their physics analyses using different techniques. These differences allow independent verification of any signs of new physics, since it should appear in each experiment regardless of the detector technology or analysis technique.

The sensitivity of a search, or the precision of a measurement, is limited both by statistics, or the amount of data used, and systematics, which includes effects from the detector and the analysis methods used. If the largest uncertainty in a search or measurement originates from a systematic, then simply taking more data with the same detector may not improve the result. Combining results from both experiments not only doubles the amount of data used, which decreases the statistical uncertainty, but it may also reduce the total systematic uncertainty since the effects from each detector are largely independent. Combinations between the Tevatron experiments have helped improve the sensitivity of searches for the Higgs boson, the measurement of the mass of the W boson and more. The latest preliminary combined result from the CDF and DZero collaborations provides the best measurement of the unique production rate for top quark pairs at the Tevatron. These combined results will prove to be part of the legacy of the Tevatron, providing important information that will constrain future models of physics.

Mike Cooke

The CDF and DZero collaborations worked together on this analysis.