‘All systems go’ in the search for the Higgs boson

This evidence for diboson production at DZero is an important test of the analysis techniques that are used to search for the Standard Model Higgs Boson.

On May 22, 1969, the Apollo 10 Lunar Module dipped to just 47,400 feet above the lunar surface during the “dress rehearsal” for the following mission that landed mankind on the moon two months later. The Apollo 10 mission collected the final data needed to calibrate the lunar module’s guidance systems for a moon landing and successfully tested all other aspects of the following moon-landing mission. A similar dress rehearsal was just completed by the DZero collaboration, but the ultimate goal of our mission is to discover, or rule out the existence of, the Higgs boson.

Below a mass of 135 GeV, a Standard Model Higgs boson would most often decay into a pair of bottom quarks—a difficult signature to pick out from the backgrounds at a hadron collider. To get a handle on the signal in this low-mass region we look for events where a Higgs boson is produced with one of the weak force carriers, a W or Z boson. The decay of that weak force carrier into leptons, in combination with the bottom quarks produced by the Higgs boson, helps flag our signal events. But backgrounds still dominate and we rely on advanced analysis techniques to perform our search. This includes forming a powerful signal discriminant by combining many variables, which individually show only mild separation between signal and background.

We can show that these advanced techniques work by applying the same strategy to look for a Standard Model signal with the same final state as our low-mass Higgs boson search. A Z boson can decay into two bottom quarks, and they can be produced in association with either a W boson or another Z boson. This specific mode of diboson production and decay occurs at roughly four times the rate of the potential Higgs signal. Using the same techniques as in the low-mass Higgs boson search, the DZero Higgs group has just produced the first evidence for this mode of diboson production.

—Mike Cooke

This analysis is the result of combined efforts from all of the low-mass Higgs boson search teams at DZero.
Kin Yip, Brookhaven National Laboratory, plays an important role in the DZero collaboration’s analysis efforts by organizing the monitoring and support of our data handling and storage systems.