|Rare processes that produce a single top quark at a time can give insight into the nature of the weak force.|
Albert Einstein once stated, “The pursuit of truth and beauty is a sphere of activity in which we are permitted to remain children all our lives.” A recent analysis at DZero takes his advice in a literal search for truth and beauty.
While top quarks are most commonly produced in pairs via the strong force, the W boson, a weak force carrier, will rarely decay into a solitary top quark (also known as a truth quark) and a bottom (or beauty) quark. Certain models of new physics predict that this mode of single-top quark production would be enhanced with respect to the Standard Model. By taking Einstein’s advice, DZero analyzers aim to uncover truth and beauty in the universe by observing the simultaneous production of truth and beauty quarks.
Quarks made in a collision turn into sprays, or jets, of particles. Jets produced from a bottom quark can be identified because they tend to be offset by a couple millimeters from the rest of the particles produced in an event. After selecting events that include a W boson signature and bottom quark jets, there are nearly 50 times as many background events as signal. To enhance the sensitivity of their analysis, the analyzers used three independent advanced techniques to discriminate signal from background and then combined the output of all three into a final powerful discriminant.
After examining the DZero Run II data, the analyzers found a significant excess of events above the background prediction and report the first evidence for this mode of single-top quark production. In addition, they presented an improved measurement of another production mode, in which the top and bottom quarks are accompanied by a third quark, and refined an independent measurement of the way the weak force interacts with top and bottom quarks. As part of the legacy of Einstein’s appeal to our curiosity, these new measurements of truth and beauty become part of the Tevatron’s legacy and provide important constraints on future models of new physics.
|These physicists made major contributions to this analysis.|
|Many analyses, like the one above, rely on the DZero b-jet identification group in order to select events that have jets that originated from bottom quarks.|