Do the top quark and the Higgs boson have a special relationship?

Particles in love.

The Higgs boson gives mass to fundamental particles, and so it likes to interact the most with the most massive particles. The top quark, discovered by CDF and DZero in 1995, is the most massive fundamental particle known, and its large mass could indicate that it has a special relationship with the Higgs boson. If so, learning about that relationship will be one of the most important tasks in understanding the Higgs boson and how it produces mass. One way to investigate this is to look at how often a Higgs boson appears in collisions that produce top quarks. The Standard Model predicts how often this should occur, and any new interaction between the Higgs boson and the top quark could alter that rate.

The CDF group at The Ohio State University has performed a pioneering search for Higgs bosons in events with top quarks. This search builds on previous CDF analyses by applying techniques developed in top quark studies and in other Higgs searches. The presence of the distinctive top quark pair sets this Higgs search apart by allowing us to include all the decay modes of the Higgs boson. Other Higgs searches employ only one decay mode, so this new technique boosts the sensitivity of this analysis.

We use the entire CDF data set and select events with a signature that includes a lepton, jets and missing transverse energy. These events are subdivided according to the number of jets and b-tagged jets in order to maximize sensitivity to the Higgs signal, and we employ an advanced mathematical technique to determine which events are most similar to Higgs events. Although we do not observe anything unexpected, we are able to put limits on how often top quark events also contain a Higgs boson and so constrain how special the relationship between the Higgs boson and the top quark might be.

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—edited by Andy Beretvas

The figure shows the results for data and simulations that have six or more jets and three or more b-tagged jets. The signal model is for a Higgs of mass 125 GeV/c².

These CDF physicists contributed to this data analysis. Top row from left: Jake Connors (now at Harvard University), Jon Wilson (now at University of Michigan), Homer Wolfe (The Ohio State University). Bottom row from left: Brian Winer and Richard Hughes, both from The Ohio State University.