A joint Fermilab/SLAC publication

Europe reaches the top, err, the top reaches Europe

07/23/10

It might be a long way to the top, but the LHC experiments are already half-way there. Today at the International Conference on High Energy Physics in Paris, the CMS and ATLAS experiments presented their first top quark candidates. These candidates are collisions that have all the hallmarks of having produced top quarks, but the experiments don't yet have enough data to be 100% sure that the events created top quarks that decayed into other particles, rather than another type of event.

"The signal is starting to rise from the background," notes Tim Christiansen from CMS.

The top quark, the heaviest particle in the Standard Model, was discovered at Fermilab's Tevatron in 1995. The CDF and DZero experiments on the Tevatron are still busy measuring its properties in detail (one of this morning's parallel sessions had several talks on its width, mass and likely couplings to particles of and beyond the Standard Model). Now the LHC experiments are joining them on the way to explore the top: both CMS and ATLAS showed selected candidate events of top quark pairs.

Finding top quarks at the LHC is exciting because the top is the last, and heaviest, particle that the LHC needed to add to its list of 'rediscoveries'. It is also an important partner in the hunt for all sorts of new physics. The better the top and its behavior are understood the easier it will be to distinguish events that involve direct top quark production from events that involve, for example, the Higgs or supersymmetric particles.

The top at ATLAS?

The top at ATLAS?

The top at CMS?

The top at CMS?

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