Higgs, SUSY and taus, oh my!

The DZero Result of the Week describes rather complex measurements. The accessible language can sometimes mask the true difficulties scientists face in searching for answers.

Making a physics measurement is hard—even for an analysis that doesn’t confirm a theory. Scientists are searching for evidence that would support two popular theories—supersymmetry and Higgs bosons. Today’s article mixes the two. Like all measurements, this is a challenging endeavor.

The first step is to figure out ways to select the right collisions to record. After all, we only write 0.01 percent of the collisions to tape. Assuming that we selected the correct collisions and the detector is functioning properly, finding events with a supersymmetric Higgs boson is extremely challenging. From the billions of recorded events, only a handful might have the desired characteristics. And to even try to identify the desired events requires tremendous care and the assimilation of a lot of information.

For instance, the simplest extension of the Standard Model that includes supersymmetry suggests that perhaps Higgs bosons might frequently decay into tau leptons. Tau leptons are the heaviest cousin of the familiar electron. However, tau leptons are unstable and can decay into muons (another electron cousin), electrons or even charged pions.

To identify tau leptons, we combine information from tracking and energy-measuring detectors and occasionally the muon detection system. While identifying the events that contain tau leptons is difficult, DZero scientists can do that. They have then exploited this capability to search for events in which the tau lepton came from supersymmetric Higgs bosons.

DZero scientists also made an additional measurement, searching for supersymmetric Higgs bosons that are made simultaneously with a bottom quark. Finding bottom quarks poses its own interesting technical challenges, as we must identify where it decayed, just millimeters after it was created.

These searches did not confirm the Higgs bosons in the simplest supersymmetric model, but they did provide valuable constraints on the theory. Despite not finding exactly what we were looking for, our ability to narrow the field is an invaluable contribution. Knowing what something isn’t is an important part of finding out what it is.

Don Lincoln

These physicists performed these analyses.
An analysis as tricky as this requires clever algorithms to select the interesting events from the deluge of data seen by the detector. These physicists are responsible for the operation of the trigger that connects DZero tracking detectors with the energy measuring ones.