Moriond 2012: Straight to the top

A variety of new measurements presented at Moriond are helping physicists to close in on the mass of the top quark

Friday’s sessions concerned the top quark, whose discovery at Fermilab in March 1995 was reported two weeks later at Moriond. The LHC and Tevatron experiments presented the latest measurements of top-quark production and decays.

Top-quark events form part of the background for Higgs searches. Since it is the heaviest known elementary particle, finding the precise mass of the top quark will help to validate a Standard Model Higgs, if it exists.

“We want to measure as many of the top quark's properties as possible, as precisely as possible,” says Alison Lister, from University of Geneva, who presented some LHC results.

The LHC experiments presented a variety of new top-quark results. Among them was a measurement by ATLAS of the mass of the top quark using events with a single lepton. CMS presented the most precise measurement of the mass of the top quark by any LHC experiment to-date, using events with a single muon. CMS also studied a potential mass difference between the top quark and antiquark, looking for signs of CPT violation. They found a discrepancy still dominated by uncertainty, but expect to reduce these error margins by examining their complete, largest dataset so far recorded.

The Tevatron experiments presented results using the full Tevatron dataset, including the world’s most precise measurement of the mass of the top quark. The top quark will always be a legacy of the Tevatron experiments, which will continue to provide a substantial contribution to the world average for years to come.